Everything Auto

Repair Guide: Lights, Fuses & Flashers

2008-03-10T13:26:00.000-07:00

Modern vehicles use dozens of bulbs to light everything from the road to the ashtray. Servicing the system is easy; over half of all lighting problems are caused by burned out bulbs, corroded sockets or burned out fuses.

The first step in understanding a vehicle's lights, fuses and flashers is to learn about basic electricity. For more information on electrical circuits, how they work and how to troubleshoot them, please refer to the information on "Understanding and Troubleshooting Electrical Systems" elsewhere in this manual

Light Bulbs
See Figures 1, 2, 3 and 4

Small bulbs, used for most automotive applications, come in several basic types-single contact bayonet base, double contact bayonet base with opposed or staggered indexing lugs, cartridge types for a small, flat installation, and wedge-base light bulbs.

Small bulbs show a broken filament when burned-out and are easily replaced. Turn them about ¼ turn and pull them from the socket. The single contact bayonet base is usually used for instrument panel lights in a small snap-in socket. The major difficulty in replacing these is finding them.

The double contact bayonet base is commonly used for turn signals, parking and taillights. The staggered indexing lugs allow one-way installation so the filament connection is correct. These bulbs are reached by removing the lens or light assembly; inside the trunk is also a common place to hide the light housings.

Don't forget to install the gasket under the lens or housing, if one is used. The gasket seals out moisture, a major cause of bulb troubles. While the bulb is out of the socket, check the socket for corrosion and if necessary, clean it.

Poor grounding is a major cause of non-functioning bulbs, especially when the bulb filaments are OK. Scraping the terminal sockets and polishing the bulb contacts is frequently all that's required. Also, check the ground between the bulb housing and the fender, and between the fender and the body. The electricity has to get back to the ground (negative) side of the battery. If it can't because of poor grounding, the bulb won't work. Many times, running a ground wire from the bulb housing directly to the frame of the vehicle is easier than trying to make a ground through rusted sheet metal.

Figure 1 Examples of various types of automotive light bulbs

1. Halogen headlight bulb
2. Side marker light bulb 3. Dome light bulb
4. Turn signal/brake light bulb

Figure 2 Burned bulbs show a broken filament (arrows)

Figure 3 Depress and twist this type of bulb counterclockwise, then pull the bulb straight from its socket

Figure 4 Disengage the spring clip which retains one tapered end of this dome light bulb, then withdraw the bulb

Headlights
See Figures 5 and 6

In the good old days, headlights where the one part for the vehicle that were easy to figure out. They were round sealed beams and you either had two or four mounted on the front of your vehicle. Nothing stays simple very long. New styling brought on rectangular headlights. This alone doubled the number of possibilities. Even more design changes and lowered hood lines brought out the small rectangular and even the mini-quad (the smallest size sealed beam). This brought the possible number of sealed beam configurations to seven.

For years, European vehicles used halogen capsule headlight assemblies. It wasn't until the late 80's that the Department of Transportation (DOT) approved the use for these in U.S. vehicles. This added three new possibilities to the existing sealed beams. However, what this meant to the automaker's was that they could design composite aerodynamic headlight assemblies that could conform to every body design and they can share these common replaceable halogen capsule bulbs.

Practically all late model cars and light trucks use halogen lights. The halogen lights increase the candlepower of the headlight from 75,000 to almost 150,000 and boosts the distance a driver can see at night by almost 20% over the old tungsten lights. Automaker's started installing them on top-of-the-line models in 1980 and they went to wide spread use on 1981 and later models.

Like the old tungsten lights, the halogen lights use a tungsten filament, but it is contained in a halogen gas environment, which allows the filament to be heated to a much higher temperature to produce a much brighter and whiter light. They also require less power, so that a smaller and lighter alternator can be used.

See Figure 5 Common headlight configurations

Figure 6 Light patterns of different types of headlights

HEADLIGHT REPLACEMENT

See Figures 7, 8, 9 and 10
On most vehicles, light bulb replacement is a simple matter. On sealed beam units, the retaining ring is removed (by loosening the clamp and/or removing the retaining bolts), then the beam is pulled forward so the electrical connector can be unplugged.

Figure 7 To replace most sealed beam headlights, start by loosening the retaining ring fastener(s) . . .

Figure 8 . . . then remove the retaining ring to free the headlight

Figure 9 Pull the lamp forward and unplug the wiring harness, then install the replacement bulb

On most halogen vehicles the bulb is replaced from behind the lamp assembly. Usually it is just a matter of opening the hood, unscrewing the lock ring on the bulb socket and/or the bulb socket itself and withdrawing the assembly from the back of the lamp. Once the socket is exposed you can remove the old halogen bulb and install the replacement.

NEVER touch the glass of a halogen bulb! If you touch the glass, you fingers will leave behind natural skin oils which will create a hot spot on the bulb, burning it out LONG BEFORE the natural end of its life. Most halogen bulbs contain a metallic coated tip which can be safely handled and, of course, you can always handle it by the plastic base.

Figure 10 Most new vehicles require only halogen bulb replacement

AIMING THE HEADLIGHTS

See Figures 11, 12, 13 and 14
The headlights must be properly aimed to provide the best, safest road illumination. The lights should be checked for proper aim and adjusted as necessary. Certain state and local authorities have requirements for headlight aiming; these should be checked before adjustment is made.

About once a year, when the headlights are replaced or any time front end work is performed on your vehicle, the headlights should be accurately aimed by a reputable repair shop using the proper equipment. Headlights not properly aimed can make it virtually impossible to see and may blind other drivers on the road, possibly causing an accident. Note that the following procedure is a temporary fix, until you can take your vehicle to a repair shop for a proper adjustment.

Headlight adjustment may be temporarily made using a wall, as described below, or on the rear of another vehicle. When adjusted, the lights should not glare in oncoming car or truck windshields, nor should they illuminate the passenger compartment of vehicles driving in front of you. These adjustments are rough and should always be fine-tuned by a repair shop which is equipped with headlight aiming tools. Improper adjustments may be both dangerous and illegal.

For most of the vehicles, horizontal and vertical aiming of each sealed beam unit is provided by two adjusting screws which move the retaining ring and adjusting plate against the tension of a coil spring. There is no adjustment for focus; this is done during headlight manufacturing.

On vehicles with composite headlights, the assembly is bolted into position, no adjustment should be necessary or possible. Some applications, however, may be bolted to an adjuster plate or may be retained by adjusting screws. If so, follow this procedure when adjusting the lights, BUT always have the adjustment checked by a reputable shop.

Before removing the headlight bulb or disturbing the headlamp in any way, note the current settings in order to ease headlight adjustment upon reassembly. If the high or low beam setting of the old lamp still works, this can be done using the wall of a garage or a building:

Park the vehicle on a level surface, with the fuel tank about ½ full and with the vehicle empty of all extra cargo (unless normally carried). The vehicle should be facing a wall which is no less than 6 feet (1.8m) high and 12 feet (3.7m) wide. The front of the vehicle should be about 25 feet from the wall.
If neither beam on one side is working, and if another like-sized vehicle is available, park the second one in the exact spot where the vehicle was and mark the beams using the same-side light. Then switch the vehicles so the one to be aimed is back in the original spot. It must be parked no closer to or farther away from the wall than the second vehicle.
Perform any necessary repairs, but make sure the vehicle is not moved, or is returned to the exact spot from which the lights were marked. Turn the headlights ON and adjust the beams to match the marks on the wall.
Have the headlight adjustment checked as soon as possible by a reputable repair shop.
If aiming is to be performed outdoors, it is advisable to wait until dusk in order to properly see the headlight beams on the wall. If done in a garage, darken the area around the wall as much as possible by closing shades or hanging cloth over the windows.
Turn the headlights ON and mark the wall at the center of each light's low beam, then switch on the brights and mark the center of each light's high beam. A short length of masking tape which is visible from the front of the vehicle may be used. Although marking all four positions is advisable, marking one position from each light should be sufficient.

Figure 11 Location of the aiming screws on most vehicles with sealed beam headlights

Figure 12 Example of headlight adjustment screw location for composite headlamps

Figure 13 Low-beam headlight pattern alignment

Figure 14 High-beam headlight pattern alignment

Repair Guide: Fasteners (Part 2 of 2)

2008-03-10T13:23:00.000-07:00

Nuts

There is a variety of nuts used on vehicles. Slotted and castle (castellated) nuts are designed for use with a cotter pin. These are mainly used for various suspension and wheel bearing fasteners, where it is extremely important that the nuts do not work loose.

Other nuts have a self - locking feature. A soft metal or plastic collar inside the nut is slightly smaller than the bolt threads. When the nut is turned down, the bolt cuts a thread in the collar and the collar material jams in the bolt threads to keep the nut from loosening.

Still other varieties of nuts include jam nuts and speed nuts. A jam nut is merely a second nut which is tightened against the first nut in order to hold the first nut in place. Jam nuts are widely used where an adjustment is involved. A speed nut is a rectangular piece of sheet metal that is pushed down over a screw or stud.

Lockwashers

A lockwasher is a split or toothed washer. It is usually installed between a nut or screw head, and a flat washer or the actual part and is used to help keep a nut or screw from loosening in service. The split washer is crushed flat and locks the nut in place by spring tension, while the toothed lockwasher, usually used for smaller bolts, provides many edges to improve the locking effect.

Cotter Pins

Cotter pins are used with slotted or castle nuts to lock the nut in position (preventing it from loosening or coming off in service). When used, the stud or bolt has a hole in it. When the nut is tightened, you align the slots with the hole so that a pin can be inserted. After the cotter pin is inserted through the nut and bolt, the legs of the cotter pin are bent over to lock the pin in place.

Loosening Seized Nuts and Bolts

See Figure 15
Occasionally, nuts and bolts that are rusted resist the ministrations of mere mortals and refuse to budge. Most of the time, penetrating oil or a sharp rap with a hammer will loosen stubborn nuts.

Another method, used in extreme cases, is to saw away two sides of the nut with a hacksaw. The idea is to weaken the nut as much as possible by sawing away two sides as close to the bolt as possible without actually damaging the bolt threads. A wrench will usually remove the remaining portion of the nut. Another option to this method is a special tool called a nutcracker. This tool often resembles a "C" - clamp with a chisel tip (other versions of this tool may be completely round with a tip at the opposite end of the threaded portion). Tightening this tool against the nut splits the nut and it then can be easily removed with a wrench. Figure 15 "C"-clamp type nut cracker (top) and impact driver (bottom) can be used to remove stubborn nuts and bolts

Removing Broken Bolts
See Figure 16

Unfortunately for the do - it - yourselfer learning the feel for how tight is too tight is an acquired skill. Breaking bolts is an unfortunate learning experience for most new mechanics. Most often, the original threads are still in satisfactory condition, however there is no longer any means to turn the bolt. When this occurs you can try to drill the bolt out and rethread the hole using a tap. However, this would probably cause you to go to the next size bolt.

The more common method to remove a broken bolt is a tool called a bolt extractor, often referred to as an Easy - Out®. Bolt extractors are available in various shapes and sizes, and are often sold in kits. You will need to know the original bolt size to select the correct tool. Once selected you will drill a small hole in the center of the bolt. Then you will insert and lightly tap the tool into the hole until it is snug. Finally, you can turn the tool and hopefully the remains of the bolt removing them from the hole. Figure 16 Bolt or screw extractors come in a variety of shapes and sizes

Repairing Damaged Threads
See Figures 17, 18, 19, 20 and 21

Several methods of repairing damaged threads are available. Heli - Coil®(shown here), Keenserts® and Microdot® are among the most widely used. All involve the same principle - drilling out stripped threads, tapping the hole and installing a pre - wound insert - making welding, plugging and oversize fasteners unnecessary.

Two types of thread repair inserts are usually supplied - a standard type for most inch - coarse, inch - fine, metric - coarse and metric - fine thread sizes and a spark plug type to fit most spark plug port sizes. Consult the individual manufacturer's catalog to determine exact applications. Typical thread repair kits will contain a selection of pre - wound threaded inserts, a tap (corresponding to the outside diameter threads of the insert) and an installation tool. Spark plug inserts usually differ because they require a tap equipped with pilot threads and a combined reamer/tap section. Most manufacturers also supply blister - packed thread repair inserts separately plus a master kit containing a variety of taps and inserts plus installation tools.

Before effecting a repair to a threaded hole, remove any snapped, broken or damaged bolts or studs. Penetrating oil can be used to free frozen threads; the offending item can be removed with locking pliers or with a screw or stud extractor. After the hole is clear, the thread can be repaired. Figure 17 Damaged bolt holes can be repaired with thread with thread repair inserts

Figure 18 Drill out the damaged threads with the specified bit. Drill completely through the hole or to the bottom of the blind hole.

Figure 19 With the tap supplied, rethread the hole to receive the threaded insert. Keep the tap well oiled and back the tap out frequently to avoid clogging the threads.

Figure 20 Screw the thread insert onto the thread installation tool until the tang engages the slot. Screw the insert into the tapped hole until it is ¼-½ turn below the top surface. After installation break the tang off with a hammer and punch.

Figure 21 In some cases threads can be restored by running a tap in the hole, or a die on the bolt

Repair Guide: Fasteners (Part 1 of 2)

2008-03-10T13:12:00.000-07:00

See Figure 1

In most applications, fasteners on vehicles may be reused providing they have not been damaged during a repair. However, in certain special applications where stretch bolts or torque prevailing nuts are used these fasteners must be replaced.

Threaded fasteners are the basic couplers holding your vehicle together. There are many different kinds, but they all fall into three basic types:

Bolts - Bolts go through holes in parts that are attached together and require a nut that is turned onto the other end. A lock - washer of some sort is usually used under the nut.
Studs - Studs are similar to bolts, except that they are threaded at both ends (they have no heads). One end is screwed into a threaded hole and a nut is turned onto the other end. Lock - washers are usually used under the nuts.
Screws - Screws are turned into drilled or threaded holes in metal or other materials.

There are a great variety of screws and bolts, but most are hex headed or slot headed for tightening. Because the fastener is the weakest link in an assembly, it is useful to know the relative strength of the fastener, determined by the size and type of material. It is also important to understand the sizes of bolts, to avoid the expense and work of re - threading stripped holes. Figure 1 Keep an assortment of fasteners and hardware neatly sorted in tackle boxes

Screws

See Figures 2 and 3
Screws are supplied with slotted, Phillips, Torx® or Allen heads for screwdrivers or with hex heads for wrenches. Most of the screws used on cars and trucks are sheet metal, hexagon or pan type. Occasionally, you'll find a self - tapping sheet metal screw, with slots in the end to form a cutting edge. These types cut their own threads when turned into a hole.

The size of a screw is designated as 8-32, 10-32 or ¼-32. The first number indicates the size of the thread at the root or minor diameter (the diameter of the screw measured from the bottom of the threads on each side) and the second number indicates the number of threads per inch. Figure 2 Common screw and bolt head types

Figure 3 Screw and bolt measurement terms

Torx® Fasteners

See Figure 4
Torx® fasteners have a star shaped head of either an internal or an external design.

These fasteners come in three different types. The most common being internal, these fasteners require a star shaped driver and are frequently found on headlight retainers and adjusters. The second type is external, these fasteners require a star shaped socket and may be found in odd locations such as the wheel cylinder retaining bolts. The third type is tamper resistant, which are used in places that manufacturer's are very serious about avoiding a Do - It - Yourselfer (DIYer) from touching. These look similar to the internal type however, they have a pin in the center of the fastener preventing the use of the standard Torx® driver. They may be found on components that are meant to be serviced only by authorized repair centers. Figure 4 Two different types of Torx® fasteners.

SAE Bolts

See Figures 5, 6 and 7
Many bolts that were once used on domestic cars and trucks maybe measured in inches, and standards for these bolts were established by the Society of Automotive Engineers (SAE). Special markings on the head of the bolt indicate its tensile strength (resistance to breaking). The SAE grade number, corresponding to the special markings, is an indication of the relative strength of the bolt. Grade 0 bolts (no markings) are usually made of a mild steel and are much weaker than a grade 8, usually made from a mild carbon steel alloy, though a grade 0 or 2 bolt is sufficient for most fasteners.

SAE fasteners are also identified by size. As an example, a 3/8-24 bolt means that the major (greatest) thread diameter is 3/8 inch and that there are 24 threads per inch. The head diameter is always 316inch larger than the bolt diameter. A ½16 bolt would be ½ inch in diameter and have 16 threads per inch. More threads per inch are called "fine" threads and less threads per inch are "coarse" threads. Generally, the larger the bolt diameter, the coarser the threads. There are actually six different classes of threads, but most bolts are Unified National Coarse (UNC) or Unified National Fine (UNF). The term "Unified" refers to a thread pattern to which US, British and Canadian machine screw threads conform. Figure 5 Fasteners commonly found on automobiles

Figure 6 SAE bolt head markings indicate their relative strength

See Figure 7 SAE standard torque specification chart.

Metric Bolts

See Figures 8 thru 14
The International Standards Organization (ISO) has designated the metric system as the world standard of measurement.

As far back as the early 1970's when Ford introduced the 2300cc, 4 - cylinder engine in the Pinto, the use of metric fasteners have become more prevalent in domestic vehicles. Probably the majority of domestic vehicles on the road today have more metric fasteners than the inch - size (SAE) type and almost all the fasteners on vehicles currently being produced are metric.

The mixture of metric and SAE fasteners on the same vehicle means that you have to be very careful when removing bolts to note their locations and to keep metric nuts and bolts together. At first glance, metric fasteners may appear to be the same size as their SAE counterparts, but they're not. While the size may be very close, the pitch of the threads (distance between threads) is different. It is possible to start a metric bolt into a hole with SAE threads and run it down several turns before it binds. Any further tightening will strip the threads. The opposite could occur also; a nut could be run all the way down and be too loose to provide sufficient strength.

Fortunately, metric bolts are marked differently than SAE bolts. An ISO metric bolt larger than 6 mm in diameter has either "ISO M" or "M" embossed on top of the head. In addition, most metric bolts are identified by a number stamped on the bolt head, such as 4.6, 5.8 or 10.9. The number has nothing to do with the size, but does indicate the relative strength of the bolt. The higher the number, the stronger the bolt. Some metric nuts are also marked with a single - digit number to indicate the strength, and some may have the M and strength grade embossed on the flats of the hex.

Metric nuts with an ISO thread are marked on one face of the hex flats with the strength grade (4, 5, 6, 8, 12, and 14). Some nuts with a 4, 5 or 6 strength grade may or may not be marked.

A clock face system is used as an alternate means of strength grade designation. The external chamfers or faces of the nut are marked with a dash at the appropriate hour mark corresponding to the relative strength grade. One dot indicates the 12 o'clock position and, if the grade is above 12, 2 dots identify 12 o'clock.

The size of a metric fastener is also identified differently than an SAE fastener. A metric fastener could be designated M12 x 2, for example. This means that the major diameter of the threads is 12 mm and that the thread pitch is 2 mm (there are 2 mm between threads). Most importantly, metric threads are not classed by number of threads per inch, but by the distance between the threads, and the distance between threads does not exactly correspond to number of threads per inch (2 mm between threads is about 12.7 threads per inch).

The 25 standard metric diameter and pitch combinations are shown here. The first number in each size is the nominal or root (minor) diameter (mm) and the second number is the thread pitch (mm).

Remember that the nominal bolt diameter is the measurement of the bolt diameter as taken from the bottom of the threads NOT the top (which would be major diameter). Figure 8 A thread gauge will instantly identify the thread size

Figure 9 Metric grade to SAE grade comparison
Metric Grade	Nominal Diameter (mm)	Corresponds to SAE Grade
4.6	M5 thru M36	1
4.8	M1.6 thru M16	-
5.8	M5 thru M24	2
8.8	M16 thru M36	5
9.8	M1.6 thru M16	-
10.9	M5 thru M36	8
12.9	M1.6 thru M36	-

Figure 10 Metric bolts are marked with numbers that indicate the relative strength of the bolt. These numbers have nothing to do with the size of the bolt.

Figure 11 Typical ISO bolt and nut markings

25 Standard Metric Diameter and Pitch Combinations
Figure 12. The 25 standard metric diameter and pitch combinations
M1.6 x 0.35	M20 x 2.5
M2 x 0.4	M24 x 3
M2.5 x 0.45	M30 x 3.5
M3 x 0.5	M36 x 4
M3.5 x 0.6	M42 x 4.5
M4 x 0.7	M48 x 5
M5 x 0.8	M56 x 5.5
M6.3 x 1.0	M64 x 6
M8 x 1.25	M72 x 6
M10 x 1.5	M80 x 6
M12 x 1.75	M90 x 6
M14 x 2	M100 x 6

Figure 13 Thread forms replaced by ISO Metric

BSW	BSF	UNC	UNF	ISO Metric Size


-	-	10	10	M5
3/16	3/16	-	-	-
-	-	12	12	M6
1/4	1/4	1/4	1/4	M6
5/16	5/16	5/16	5/16	M8
3/8	3/8	3/8	3/8	M10
7/16	7/16	7/16	7/16	M10
1/2	1/2	1/2	1/2	M12

Buyer's Guide to Parts and Supplies (Part 2 of 2)

2008-03-10T12:53:00.000-07:00

Sources for Parts

There are many sources for the parts you will need. Where you shop for parts will be determined by what kind of parts you need, how much you want to pay, and the types of stores in your neighborhood.

NEW CAR DEALERS

New vehicle dealers usually have parts for your vehicle, but the prices are usually higher than other sources. The dealer carries what are known in the auto trade as Original Equipment Manufacturer (OEM) parts. OEM parts are those supplied by the vehicle manufacturer and are the same parts installed on the vehicle when it was built. Because of the higher overhead expenses, these parts are generally a little more expensive than the same item available through other outlets.
The higher cost of OEM parts does not necessarily indicate a better value, or higher quality. Automotive jobbers and auto discount stores regularly stock high - quality replacement parts in addition to OEM parts. Although manufacturers will recommend that you use OEM parts for replacement or service work, they will also specify that you can use an equivalent replacement part. Many replacement parts are made by or sold by reputable companies and are built to the same specifications as OEM parts. In many cases, replacement parts may even be identical to OEM parts, since many parts manufacturers sell parts to vehicle makers as OEM parts and also sell the same part to other companies, who market the part under a different brand name. The parts you have to be careful of are "gypsy" parts, which are discussed later in this section. Fortunately there are very few of them.

There are some parts for your vehicle - cylinder heads, crankshafts, body parts, and other slow movers - that you will be unlikely to obtain anywhere but at your dealer. These parts are not sold in sufficient quantities to make it attractive for any other outlet to stock them. Many of these parts may be special ordered.

SERVICE STATIONS

Your local service station can supply you with many of the common parts you require; though they stock these parts mainly for their own use in the repair end of the business. The problem, from the consumer's standpoint, is the cost - it will be high. The reason is that the service station operator buys the same part from a jobber that you can buy over the counter. Although he buys at a discount, he must make a profit on the resale of the item, whether through direct sale of the item or as part of repair charges. Really, when your service station sells parts to you over the counter, they are competing with the local parts stores and discount merchandisers, and most service stations do not buy or sell parts in sufficient volume to offer a competitive price. They are in business to sell "service," not to sell parts.

PARTS JOBBER

The local parts jobber, who is usually listed in the yellow pages or whose name can be obtained from the local gas station, supplies most of the parts that are purchased by service stations and repair shops. He also does a sizeable business in over - the - counter parts sales for the do - it - yourselfer, and this may constitute as much as 30% to 50% of his business.
The jobber usually has at least two prices - one for the local mechanic or service station and an over - the - counter retail price. The reason for this is that local mechanic, like the service station, does not pay the retail price for a given part. They pay less than retail (a mechanic's discount may range from 15-40% depending on the item) and mark up the price of the part to their customer, making a profit on the resale. Many jobbers will offer you a 10%-15% discount off the retail prices on over - the - counter sales, and most jobbers run periodic sales on both private brand and brand name do - it - yourself items.

The prices charged by jobbers are usually lower than the new vehicle dealers and service stations but slightly higher than discount or mass merchandisers. The reason is that the jobber is used to dealing with professional mechanics and usually sells name brand or OEM parts. His volume is such that he sells more than a service station, but less than a discount merchandiser does, and thus his prices fall somewhere between the two. The people who work the counters in the jobber stores and discount stores know about vehicles - often more than the salesperson in the auto section of a department store. Unless they are extremely busy or very rushed, they can usually offer valuable advice on quality parts or tools needed to do the job right.

AUTOMOTIVE CHAIN STORES

Almost every community has one or more convenient automotive chain stores. These stores often offer the best retail prices and the convenience of one - stop shopping for all your automotive needs. Since they cater to the automotive do - it - yourselfer, these stores are almost always - open weekday nights, Saturdays, and Sundays, when the automotive jobbers are usually closed.
Chain stores are the automotive "supermarkets." Hardly a week goes by that they are not running advertised specials or a seasonal promotion of some type. The ads normally appear in the local newspapers and offer substantial savings on both name and store brand items. In contrast to the traditional jobber stores, where most merchandise is located behind the counter, you can walk through the auto chain stores and browse among most products, picking and choosing from a large stock of brand names.

Prices in the auto chain stores will normally be competitive with the discount stores and mass merchandisers, and they will usually be slightly lower than the jobber will. Counter personnel working in the chain and jobber stores are usually familiar with their products and common automotive problems and can offer good advice.

DISCOUNT STORES

The lowest prices for parts are most often found in discount stores or the auto department of mass merchandisers, such as K - Mart, Sears, and Wal - Mart. Parts sold here are name and private brand parts bought in huge quantities, so they can offer a competitive price. Private brand parts are made by major manufacturers and sold to large chains under a store label.
You have to have a good idea of what you're looking for when you buy from these outlets. Many are self - serve, in direct contrast to the older, traditional jobbers where they still look up the part number and get the part for you.

AUTO JUNKYARD

Wrecking yards, junkyards, salvage yards, previously owned parts yards - call them what you will - are good sources of parts, particularly for older vehicles or limited budgets, although most parts available from salvage yards are beyond the scope of this book. Auto wrecking yards range from the incredibly sophisticated computer - run inventories to stumblebum one - man operations where nobody knows exactly what they have except the inevitable snarling dog.
In most cases, don't expect the wrecking yards to supply the smaller parts. They prefer to deal in complete assemblies. Among the better deals in wrecking yards are engines, transmissions, rear axles, body parts, and wheels. The cost of these parts from a yard is generally about one - half the cost of new parts. Most junkyards are not interested in selling carburetors, voltage regulators, and other small parts, but if they do, their cost will be negligibly less than the cost of rebuilt parts, and rebuilt parts are a far better deal.

Some wrecking yards may have two prices - one if they remove the parts and one if you do it. Most yards will prefer to remove parts themselves, but be careful. Time is money when removing parts, so a lot of yards, particularly the less organized, will remove an engine or rear axle with a cutting torch instead of unbolting it. This makes it necessary for you to buy small parts, such as motor mounts, brake lines, spring hangers, and other hardware, that were destroyed by the cutting torch.

Kinds of Parts

NEW OR REBUILT PARTS

Many times, you will be required to return your old starter, alternator, fuel pump, or carburetor when you buy a new one. These old parts are returned to a professional parts rebuilding service and are reconditioned to be sold over the counter as remanufactured or rebuilt parts.
Most parts stores will carry both new and rebuilt parts. There is nothing wrong with buying remanufactured parts. Many are just as good as the new ones but can be bought at considerable savings. Compare the price and guarantee on a remanufactured part with that of a new part. In general, the higher the quality of a remanufactured part, the closer the price will be to a new part and the better the warranty.

Inordinately low prices for remanufactured parts usually mean shorter parts life and earlier failures. In this case, it will be worthwhile to spend a little extra money for higher quality.

COUNTERFEIT PARTS

Caveat Emptor - let the buyer beware - was a reasonable attitude when the buyer could easily judge the quality of the merchandise he was buying.
However, as automobiles have become increasingly sophisticated, with electronic engine control systems and other hi - tech hardware, there are fewer manifestly clear ways by which to judge the quality of replacement parts.

Reputable manufacturers of replacement parts have built their reputations of repeat business. Their products meet or exceed the Original Equipment (OE) specifications. If they don't perform, you're not going to come back and buy many more of the same. Counterfeiting, as applied to auto parts, is a broad term that covers any form of deception designed to trick the buyer into believing that he or she is purchasing a part produced by the original equipment manufacturer or a reputable aftermarket manufacturer.

Counterfeit products should not be confused with "generic or no - brand" products such as those found in the food industry. It's fully understood that these types of products are not branded products. The key to counterfeit parts lies in the fact that no attempt is made to identify the source of manufacture and that the counterfeit part and packaging closely resembles the real thing.

Packaging of reputable parts manufacturers is often unique and highly recognizable, but those who buy replacement parts by appearance or packaging alone should beware. Counterfeit parts are made to look like the real thing both in packaging and in appearance.

Counterfeit packaging usually involves the unauthorized use of a registered trademark on the packaging or the simulation of a part using original equipment characteristics and is designed to pass off generally sub - standard parts as the genuine article. Counterfeit parts have the right number of wires and connectors. They look official, durable and reliable.

However, looks are deceiving. Not only can counterfeit parts cost you money in the long run, due to premature failure or an unknown manufacturer who will not guarantee the part's performance, the shortcuts often taken in the manufacture of counterfeit parts could jeopardize your safety or the vehicle's performance. Some counterfeit brake shoes have been found deficient in braking power. Some counterfeit gas tank caps have no safety valves, designed to prevent spillage and fire in case of an accident.

How can you recognize counterfeit parts? Often, it's extremely difficult.

Buy brand - name products. A name brand manufacturer's reputation for quality can only have been earned by selling quality merchandise.
Be suspicious of packaging that very closely, but not exactly, replicates the packaging of a known, name brand manufacturer.
Recognize that in a competitive marketplace, there will be variations in price among reputable manufacturers. Nevertheless, be suspicious of extremely low prices.
If someone other than you is installing the part, ask to see the package in which it came. Even mechanics are not immune to assuming, mistakenly, that they are buying name brand replacement parts.
If possible, compare the original equipment part with the replacement part before purchasing the replacement part. There are often subtle differences between counterfeit and original equipment and reputable replacement parts.

Using Automotive Catalogs
See Figure 1

To a person looking for a part for his or her vehicle, the catalog is the most important tool to know how to use. Automotive parts catalogs are what you make them - a confusing foreign language or an easy - to - understand reference to get the correct part number, and price the first time.

Almost all manufacturers of hard parts make a catalog listing the part number, application, and sometimes the price of the item. The catalog may take the form of a large book with thousands of entries if the manufacturer makes many parts for a lot of applications, or it may be as simple as a single card if the manufacturer has relatively few variations. If you are purchasing oil filters, air filters, PCV valves, belts, hoses, and similar common parts, you will usually find the catalog near the merchandise in the parts store, though from time to time they will disappear. Wherever they are located and whatever form they take, learning to use them will assure that you get the correct part the first time, saving a lot of time and energy to return parts that don't fit.

With the age of computer databases, more and more parts look - up is done via a terminal on the parts counter. It is important to supply the operator with the correct information regarding your vehicle as discussed earlier. He will enter the vehicle only one time and have access to many different manufactures parts, as opposed to looking up the vehicle, then the part in individual printed catalogs. You may also find mini - computers in product locations on the sales floor for filters, batteries, wiper blades, etc. Figure 1 Parts catalogs, giving part number and application, are provided by manufacturers for most replacement parts

GENERAL LAYOUT

Catalogs normally contain a descriptive and dated (sometimes - coded) cover, a table of contents, index, illustrations, and then the meat of the catalog, the applications. The applications are normally arranged two ways: (l) alphabetically by vehicle name, and (2) numerically by part number. Jobbers may store their catalogs using the Weatherly filing system, a three - digit number on the front of the catalog, but this is of little interest to the do - it - yourselfer. What does interest you is the alphabetical listing of vehicles by make and model.
Many manufacturers print their parts catalogs every year, but some only print every two years and supply a supplement during the off year. It is essential to check the date of the catalog to be sure it has the latest information. Working with an outdated catalog is sometimes worse than working with no catalog at all.

LOCATING APPLICATIONS

Let's say you want to look up the spark plug for your 1996 Jeep Cherokee with a 4.0L engine. The first thing you do is find a spark plug catalog and check the date to make sure it is current. Then you look in the index for "Jeep." In this particular catalog, there is no listing by make and model in the index. The spark plug applications are broken down by Automobiles, Vans / Trucks & Buses, and several other listings. If you have an SUV or sport utility vehicle it may be listed either in the Car or Automobile section or in the Truck section depending upon the manufacturer. In this case, turn to the page starting Vans, Trucks & Buses.
Under Vans, Trucks & Buses, you'll find they are broken down into individual makes starting with Acura and working back to Volkswagen. Scan the pages until you find the heading Jeep. Under Jeep, you'll find the applications are further broken by model and year. And then 4 - cylinder and 6 - cylinder engines. Your Jeep is a 1996 Cherokee and has a 6 - cylinder, so look under the appropriate heading. Read across the column from the L6 4.0L entry and find the number of the spark plug.

ABBREVIATIONS AND FOOTNOTES

See Figure 2
If you have trouble deciphering the abbreviations used in the parts catalog, they are usually identified in the front of the catalog.

The biggest distraction in all automotive catalogs is the footnotes. Asterisks, daggers, numerals, and letters that appear after a part number or listing indicate that you are up against a footnote. If such a notation is present, you must look further for more information. Most likely, you will go to the bottom of the page for an explanation of why the notation was used. In addition, the explanation could be almost anything. Special kits, superceded parts, special applications, and a myriad of other pieces of information all are deserving of footnotes. To get the right part for your vehicle you cannot afford to skip over the footnotes. Figure 2 Catalog footnotes are important. They may contain replacement part numbers and other pertinent information.

CROSS - REFERENCE

See Figure 3
Many catalogs include a cross - reference so you can double check information. A cross - reference could be from original equipment to independent supplier part numbers, or to application by part number.

Caution should be used when cross - referencing parts. While Original Equipment Manufacturer (OEM) to an aftermarket part number is often a very accurate reference, aftermarket - to - aftermarket references should be double - checked by that particular manufactures application guide.

Figure 3 It is a good idea to check the actual number on the part, against the application catalog.

COMMON CATALOG MISTAKES

Catalogs are designed for using, not confusing, but it is not unusual for catalog users to make mistakes in tracking down part numbers. Simple goofs are the most common and costly. For instance, often the user will find the correct listing, but then he or she reads across the wrong line. On the other hand, sometimes everything is done correctly, but a mistake is made in copying or trying to remember the part number. Alternatively, you can be mixed up in using a cross - reference, or working with an outdated catalog, or overlooking a footnote. Such mistakes happen every day to even the most experienced. All you can do is try your best to avoid them.

Buyer's Guide to Parts and Supplies (Part 1 of 2)

2008-03-10T12:45:00.001-07:00

See Figure 1
Do - it - yourself has become an economic necessity for many of us. It's an opportunity to save some money and have some measure of fun working on the old buggy at the same time.

You'll find, if you haven't already, that it's easy to change the oil and filters or handle minor repairs, but you have to be sure you're getting the correct parts, at the best price.

Today, manufacturers and retailers know you're interested in do - it - yourself repairs to save money. That's why you'll find parts packaged or displayed with application charts to help you select the right parts for your vehicle.

Auto supply stores, discount and department stores, automotive jobbers, and other sources sell complete lines of quality parts for auto repair enthusiasts like you. You may want to comparison shop these outlets to see where you can get the most for your money. It's wise to compare price tags and quality all year, instead of expecting to find bargains on infrequent shopping tours. Sales on replacement parts are common. Weekly specials, holiday, and seasonal promotions all offer a chance to save on your automotive needs.

It doesn't really matter whether you buy name brand or store - brand parts. You can save a little money on the store - brand items as opposed to Original Equipment Manufacture (OEM) parts, but you may end up replacing them a little sooner if you buy too far down on the price scale.

The main thing is to be sure to get the correct part for your vehicle. An incorrect part can adversely affect your engine performance, fuel economy, and emissions, and will cost you more money and aggravation in the end. To avoid buying the parts piecemeal, many manufacturers have taken to offering do - it - yourself tune-up packages, containing, plugs, rotor, and sometimes distributor cap. Spark plug wires can be purchased already cut to length and ready to install, or as a kit, in which case you cut the necessary lengths yourself.

To get the proper parts for your vehicle, you will probably need to know some or all of the following information:

Make: Jeep, Saturn, etc.
Model: Cherokee, SL2 Sedan, etc.
Year: 1996 (example)
Engine size: The engine size may be designated in cubic inches (242, 116, etc.) or in cubic centimeters (cc) on imports (1600, 2000, etc.). Usually, it will be given in liters (4.0, 1.9, etc.). If you are not sure, there is usually a designation on the engine or under the hood that tells you the engine size. There may be a letter with the number that you should copy down, too. When in doubt write down all the information you can find it will save you repeated trips to the parts store.
Number of cylinders: 4, 5, 6, 8, etc., for example
Carburetor (or fuel injection): If the engine is carbureted, you'll need to know if the carburetor is a 1, 2, 3, or 4 barrel (abbreviated bbl) model. You may also find the word venturi (abbreviated V) used interchangeably with the word barrel when describing carburetors. On fuel injected models you may need to know which injection system is used. This is important because there are instances where a given model in the same year may have two engines with the same displacement, and the only difference may be the injection system. These are usually described on the engine in some sort of acronym SFI, SPFI, MFI, PGMFI, etc. In addition, your fuel - injected engine may be turbo - charged. These conditions will usually have ramifications that will effect other engine and fuel related parts.
Air conditioner: Yes or No
Quantity of oil: How many quarts
Engine code: Since 1981, this code has been important to all domestic and some import vehicles. The engine code is part of the 17 digit Vehicle Identification Number (VIN), which is visible through the front windshield on the driver's side. On GM, Ford and Chrysler vehicles, the engine code is the 8th digit. On many import vehicles the engine must be identified by a tag on the engine or a number stamped on the block, bell housing or other location.

Figure 1 Make copies of this chart and keep with your vehicle

QUICK REFERENCE SPECIFICATIONS

For quick and easy reference, you can use this form to Jot down frequently used information concerning parts available for your vehicle.

Tune-Up Data
Firing Order Spark Plugs: Type (Manufacturer/No.) Gap (in./mm)
Ignition Timing Vacuum (Connected/Disconnected)
Valve Clearance (in./mm) Exhaust
Capacities
Engine Oil (qts/litres) With Filter Change Type of Lubricant Cooling System (qts/litres)
Manual Transmission (pts/litres) Type of Lubricant
Transfer Case (pts/litres) Type of Lubricant
Automatic Transmission (pts/litres) Type of Lubricant
Differential (pts/litres) Type of Lubricant

Commonly Forgotten Part Numbers Use these spaces to record the part numbers of frequently replaced parts.
PCV VALVE Manufacturer Part No.	OIL FILTER Manufacturer Part No.
AIR FILTER Manufacturer Part No.	FUEL FILTER Manufacturer Part No.

Repair Guide: Tools and Supplies (Part 3 of 3)

2008-03-10T12:35:00.000-07:00

Jacks and Jackstands
See Figures 46, 47, 48 and 49

A vehicle must be raised in order to lubricate the chassis, change the oil and gain access to various parts under the vehicle. Above all, a vehicle must be raised and supported safely. Never attempt to work under a vehicle supported only by a jack.

The jack that comes with the vehicle is suitable for raising the vehicle, but is not suitable for supporting the vehicle while you work under it. Once the vehicle is raised, place safety stands under it before attempting any work.

Scissors jacks are the least expensive types of jacks. These are mechanically operated by a threaded rod that is turned inside a diamond-shaped frame. Cranking the screw causes the diamond-shaped frame to expand or contract, raising or lowering the vehicle.

Hydraulic jacks are the best and quickest means of lifting a vehicle off the ground. Hydraulic jacks run anywhere from $30–$300, depending on the size and quality of the jack. They are available as small units that can be picked up easily in one hand and placed where needed, or as large, heavy units equipped with wheels to move them about. The smaller models work slowly and tip over easier.

Hydraulic jacks use a pump to push hydraulic fluid against a ram that operates the lifting pad. They have seals that are prone to leaking. This is one good reason why you shouldn't work under a vehicle supported by a hydraulic jack. If the seals leak, the jack will lose pressure and the vehicle will slowly (or quickly) fall to the ground.

Jackstands are the safest way to support a vehicle. They are made of heavy metal, and are adjustable for different working levels. Once you have raised the vehicle to a convenient height, the Jackstands are adjusted underneath it and the vehicle is lowered onto the stands. Professional Jackstands are the easiest to use, but cost the most. Occasionally, if you're very fortunate, they can be picked up used from a service station that is going out of business.

Drive-on ramps are the alternative to jacking and supporting the vehicle. A good set of pressed steel ramps can cost as much as $40–$70, but they are often worth the expense. Be sure to check the angle of the incline on the ramps. With extensive use of front spoilers and air dams on today's vehicles, often there may be clearance problems.

Fig. 46 A hydraulic floor jack and a set of jackstands are essential for lifting and supporting the vehicle

Fig. 47 Car ramps may substitute for a jack and jackstands, however, old style ramps don't provide adequate clearance for late-model vehicles...

Fig. 48 ...new style ramps have angle adapters to allow clearance for front spoilers on many of today's vehicles.

Fig. 49 When using ramps or jackstands, always block the wheels on the opposite end of the vehicle

Shop Supplies
See Figures 50 and 51

When you plan your shop supplies, you should follow the same format as you used for your tools- if you intend to perform only basic level work, you need only acquire a minimum number of supplies, and so forth.

At the basic level, you're going to need mostly replacement fluids. Things such as motor oil, antifreeze, automatic transmission fluid and brake fluid should be kept on hand. You'll also need some clean rags or wiping towels and some hand cleaner.

At the average level, things get a little more complex. You'll probably need chassis and wheel bearing grease, spare hoses and belts, plugs, penetrating oil, parts cleaner and a variety of other supplies.

The list of supplies needed for the advanced level could be endless, but if you're operating at the advanced level, you probably already have most supplies. Look at the list prepared here, keeping in mind that it's only a partial list, and these are all just suggestions. Remember the advanced level includes all the other levels as well.

Fig. 50 Hand cleaners have gone high-tech! Lotion, cream, and even citrus. Make sure you have some on hand.

Fig. 51 Shop sealants and adhesives come in a variety of applications. Always read the package before use.

SEALANTS

See Figures 52, 53, and 54
If you're not already familiar with the terms "aerobic," "anaerobic" and "RTV", you probably should be. These are the kinds of sealant that have replaced many cork and rubber gaskets on vehicle assemblies.

The terms refer to the curing properties of the sealant. Aerobic means that the sealant cures in the presence of air and can be used on flexible flanges and between machined parts. However, it should not be used where it might squeeze out and plug small passages. Parts must be assembled immediately or the sealant will harden.

RTV sealant is another name for a type of aerobic sealant, standing for Room Temperature Vulcanizing. Aerobic sealants are often identified as RTV silicone rubber compounds, under names such as GM, GE, Permatex®, Devcon®, Dow Corning, MOPAR®, FelPro®, Loctite®, or Versa Chem®.

Anaerobic sealants are those that cure in the absence of air. In other words, the sealant will not cure (harden) until the parts are assembled and the air is denied. Anaerobic sealants are for use between smooth, machined surfaces, but should not be used between flexible mounting flanges. They should also be applied sparingly in a continuous bead to a clean surface.

Uncured aerobic or RTV sealants can be wiped off with a rag. Cured sealants can be removed with a scraper, wire brush or common shop solvents. Fig. 52 Anaerobic sealant is available in several types from a variety of manufacturers

Fig. 53 Epoxy systems are available for metal and plastics and have different drying times

Fig. 54 RTV comes in various colors indicating specific applications. Once again read the package.

Universal Thread Sealant

There are more thread sealants than can be counted. Add to these the several sealant tapes now on the market and the confusion can be great. Mechanics should be aware of the anaerobic sealant with Teflon® filler that can be used on all joints. (GM Truck has adopted it as universal sealant.) "Pipe Sealant with Teflon" is applied to threads. It creates an instant seal, but does not cure for 24 hours. This permits making changes if needed. Once hardened it prevents vibration-induced loosening.

How to Use Sealants

Anaerobics: Clean surfaces with solvent and apply bead to one surface. Material will not begin to cure until parts are assembled. Sealing is effective in half an hour. Full cure is complete in 2½–10 hours depending upon temperature. Cold slows cure.

Aerobic or Silicone sealants: Clean and dry surfaces. Apply bead and let cure for two hours. To make a gasket that will cling to only one surface, apply bead to one surface and allow it to cure. Then apply grease to other surface, and assemble. Or, to make a gasket that will bond to both surfaces, apply and assemble. This will provide maximum blowout resistance. Material will cure to depth of ¼ inch in 24 hours.

When to Use Sealants

The basic guide in choosing a sealant is the size of the gap. Anaerobic materials are used only on smooth, rigid, machine-surfaced flanges which have a total gap less than .030 inch (.301mm). Silicones are used in parts that may flex (such as metal-stamping covers) and which have gaps that are more than .030 inch (.301mm) but not more than 0.25 inch (6.35mm). Both materials are impervious to the normal automotive fluids such as gas, oil, coolants and hydraulics. Anaerobics have a temperature range of - 60–300F (15–149°C), and silicones will handle- 100– 450°F (38–232°C).

Anaerobics: Common applications for the anaerobic materials include fuel pumps, timing covers, oil pumps, water pumps, thermostat housings, oil filter adapters, manual transmission housings, differential covers and other rigid parts. Bear in mind that anaerobic materials add rigidity to the assembly because they help lock the surfaces.

Aerobic or Silicone sealants: Many silicone applications involve stamped metal housings such as oil pans, valve covers, and other parts such as intake manifolds, transmission covers, axle covers and rear main bearing seals.

Solvent release: Non-hardening sealants are used to repair cut gaskets on both rigid and flexible assemblies that operate at high temperatures up to 600°F (315°C). On semi-permanent assemblies, the materials set quickly to bolster the conventional gasket. By remaining pliable, they permit easy removal later.

Hardening sealants dry fast and hard and are used on permanent assemblies to aid the conventional gasket, particularly when the flanges are damaged.

Most sealants also aid in assembly by holding the gasket in place during assembly. When such positioning problems are extremely difficult, a gasket adhesive can be used to hold the gasket in perfect alignment during assembly.

Arranging Your Shop
See Figure 55

Obviously, the arrangement of your shop depends a great deal on just what kind of shop you have in the first place. If you have very limited floor space, careful use of wall space will be the key to allowing yourself working room. If you're like most of us, you probably have a million things in the garage already, which isn't going to help matters. Put up some shelves or get some pegboard to hang tools on. Make sure you have plenty of lighting in the garage. If you don't have enough lights, install some more. There's nothing worse than trying to work by the light of a flashlight or a trouble light. Keep the floor clean and make sure you have adequate ventilation. Keep flammable liquids outside, and anchor all the benches and any heavy equipment you may have. Fig. 55 One vehicle and two vehicle typical shop layout

Servicing Your Vehicle Safely
See Figures 56 and 57

It is virtually impossible to anticipate all of the hazards involved with automotive maintenance and service, but care and common sense will prevent most accidents.

The rules of safety for mechanics range from "don't smoke around gasoline," to "use the proper tool for the job." The trick to avoiding injuries is to develop safe work habits and take every possible precaution.

DO'S

Do keep a fire extinguisher and first aid kit handy.
Do wear safety glasses or goggles when cutting, drilling, grinding or prying, even if you have 20–20 vision. If you wear glasses for the sake of vision, wear safety goggles over your regular glasses.
Do shield your eyes whenever you work around the battery. Batteries contain sulfuric acid. In case of contact with the eyes or skin, flush the area with water or a mixture of water and baking soda, then seek immediate medical attention.
Do use safety stands (jackstands) for any undervehicle service. Jacks are for raising vehicles; jackstands are for making sure the vehicle stays raised until you want it to come down. Whenever the vehicle is raised, block the wheels remaining on the ground and set the parking brake.
Do use adequate ventilation when working with any chemicals or hazardous materials. Like carbon monoxide, the asbestos dust resulting from some brake lining wear can be hazardous in sufficient quantities.
Do disconnect the negative battery cable when working on the electrical system. The secondary ignition system contains EXTREMELY HIGH VOLTAGE. In some cases it can even exceed 50,000 volts.
Do follow manufacturer's directions whenever working with potentially hazardous materials. Most chemicals and fluids are poisonous if taken internally.
Do properly maintain your tools. Loose hammerheads, mushroomed punches and chisels, frayed or poorly grounded electrical cords, excessively worn screwdrivers, spread wrenches (open end), cracked sockets, slipping ratchets, or faulty droplight sockets can cause accidents. Likewise, keep your tools clean; a greasy wrench can slip off a bolt head, ruining the bolt and often harming your knuckles in the process.
Do use the proper size and type of tool for the job at hand. Do select a wrench or socket that fits the nut or bolt. The wrench or socket should sit straight, not cocked.
Do, when possible, pull on a wrench handle rather than push on it, and adjust your stance to prevent a fall.
Do be sure that adjustable wrenches are tightly closed on the nut or bolt and pulled so that the force is on the side of the fixed jaw.
Do strike squarely with a hammer; avoid glancing blows.
Do set the parking brake and block the drive wheels if the work requires a running engine.

DON'TS

Don't run the engine in a garage or anywhere else without proper ventilation- EVER! Carbon monoxide is poisonous; it takes a long time to leave the human body and you can build up a deadly supply of it in your system by simply breathing in a little every day. You may not realize you are slowly poisoning yourself. Always use power vents, windows, fans and/or open the garage door.
Don't work around moving parts while wearing loose clothing. Short sleeves are much safer than long, loose sleeves. Hard-toed shoes with neoprene soles protect your toes and give a better grip on slippery surfaces. Jewelry such as watches, fancy belt buckles, beads or body adornment of any kind is not safe working around a vehicle. Long hair should be tied back under a hat or cap.
Don't use pockets for toolboxes. A fall or bump can drive a screwdriver deep into your body. Even a rag hanging from your back pocket can wrap around a spinning shaft or fan.
Don't smoke when working around gasoline, cleaning solvent or other flammable material.
Don't smoke when working around the battery. When the battery is being charged, it gives off explosive hydrogen gas.
Don't use gasoline to wash your hands; there are excellent soaps available. Gasoline contains dangerous additives which can enter the body through a cut or through your pores. Gasoline also removes all the natural oils from the skin so that bone dry hands will suck up oil and grease.
Don't service the air conditioning system unless you are equipped with the necessary tools and training. When liquid or compressed gas refrigerant is released to atmospheric pressure it will absorb heat from whatever it contacts. This will chill or freeze anything it touches. Although refrigerant is normally non-toxic, R-12 becomes a deadly poisonous gas in the presence of an open flame. One good whiff of the vapors from burning refrigerant can be fatal.
Don't use screwdrivers for anything other than driving screws! A screwdriver used as an prying tool can snap when you least expect it, causing injuries. At the very least, you'll ruin a good screwdriver.
Don't use a bumper or emergency jack (that little ratchet, scissors, or pantograph jack supplied with the vehicle) for anything other than changing a flat! These jacks are only intended for emergency use out on the road; they are NOT designed as a maintenance tool. If you are serious about maintaining your vehicle yourself, invest in a hydraulic floor jack of at least a 112 ton capacity, and at least two sturdy jackstands.

Fig. 56 Always support your vehicle on jackstand while working underneath

Fig. 57 If you're using portable electric tools, make sure they're grounded, preferably at the plug by a three wire connector

TWO-WIRE CONDUCTOR
THIRD WIRE GROUNDING THE CASE THREE-WIRE CONDUCTOR
GROUNDING THRU A CIRCUIT

THREE-WIRE CONDUCTOR
ONE WIRE TO A GROUND THREE-WIRE CONDUCTOR
GROUNDING THROUGH AN ADAPTOR PLUG

Repair Guide: Tools and Supplies (Part 2 of 3)

2008-03-10T12:26:00.000-07:00

Specialty Tools
See Figures 20 thru 28

In addition to basic tools, you'll find a number of small specialty tools that will make your life as a do-it-yourselfer much easier. A battery terminal puller (for top terminal batteries) costs only a few bucks, and will save you a lot of trouble when you remove your battery cables. A combination cable and terminal cleaner is also handy. A tire pressure gauge is an absolute must if you plan to get the most wear out of your tires. Buy a good one, since tire pressure is critical to tire life. An antifreeze hydrometer is necessary to keep an eye on the state of your coolant. Fig. 20 Side terminal battery cleaning tool

Fig. 21 Battery terminal puller

Fig. 22 Top battery terminal cleaning tool

Fig. 23 Tire pressure gauges top, and tread depth gauges bottom

Fig. 24 A hydrometer is necessary to check antifreeze protection

Fig. 25 Tools from specialty manufacturers such as Lisle and Cal-Van are designed to make your job easier. Here is an assortment of brake tools.

Fig. 26 Specialty sockets are required for many sensors and axle nuts. Acquire these as the job calls for it.

Fig. 27 Special pullers are required for various applications. Often these tools can be rented from a tool rental or auto parts store.

Fig. 28 Interior door handles and panels often require special clip removers

General Maintenance Tools

The list of general maintenance tools is practically endless, depending on the degree of your involvement. However, a basic list for the average do-it-yourself mechanic would include:

An oil filter wrench,
A grease gun,
A container for draining oil,
A suction gun,
Battery terminal cleaners, and
Many rags for cleaning up the inevitable mess.

Oil filter wrenches come in various types. The strap wrench is the most common and will handle most filters. A more sophisticated filter wrench combines a strap or band wrench with a ratchet drive. This type is useful when the filter is located in an out-of-the-way place. Many oil filters on front wheel drive vehicles, can only be removed with this type of wrench. The other types of filter wrenches are applied to the end of the oil filter, and both are designed for use with a ratchet drive.

A funnel is the best way to get oil from the bottle into the engine with a minimum of mess. Any other way will surely result in oil spilled on the engine, which will turn to smoke when the engine gets hot. Other types of fillers have flexible spouts for filling automatic transmissions and other hard-to-reach filler tubes.

A grease gun is also the only way to lubricate the vehicle's chassis. The grease gun comes in various sizes that accept cartridges of different kinds of grease and a variety of flexible and odd-shaped fittings to reach hard-to-get-at grease nipples.

A fluid suction gun is almost a necessity to add (or remove) oil from a differential. The filler plugs on differentials and manual transmissions are frequently in a spot that you cannot fill directly from the container. You will probably have to transfer the fluid from the container into a suction gun first. The fluid is also frequently heavy oil, which does not flow easily, which further complicates the problem. To remove fluid from a unit without a drain plug, a suction gun is invaluable.

Battery cleaning tools are inexpensive and make battery terminal cleaning easier and quicker. They generally come in two styles, one for top terminals and one for side terminals. The one for side terminals is nothing more than a miniature wire brush, which you can easily substitute. Fig. 29 Oil filter wrenches come in a number of styles. You will have to experiment to find the correct combination for your vehicle.

Fig. 30 Lubrication tools- suction gun, grease gun, and bearing packers

Fig. 31 This type of oil drain pan enables you to take your waste oil to a recycling station. Remember to drain the filter into the pan.

Tune-Up Tools

The word "tune-up" actually applies only to older vehicles, on which you can perform the traditional work associated with "tune-up"- spark plug replacement, ignition contact point replacement, dwell adjustment, ignition timing adjustment and carburetor idle and mixture adjustment.

For today's vehicles, engine performance maintenance is a more accurate term. Modern vehicles are equipped with electronic ignition (no points) and an on-board computer that automatically adjusts the ignition timing fuel mixture and idle speed. In fact, on modern computer-controlled vehicles, it's usually impossible to adjust these yourself:

If you plan to do your own engine performance maintenance, there are some specialized tools you are going to need. You'll need a round wire gauge to check and set the plug gap, a timing light (if your ignition timing is adjustable), a dwell-tach or just a tach (to set idle speed if it is adjustable). A compression gauge is also handy, though not necessary.

An important element in checking the overall condition of your engine is to check compression. This becomes increasingly more important on high mileage vehicles. Compression gauges are available as screw-in types and hold-in types. The screw-in type is slower to use, but eliminates the possibility of a faulty reading due to escaping pressure. A compression reading will uncover many problems that can cause rough running. Normally, these are not the sort of problems that can be cured by a tune-up. Vacuum gauges are also handy for discovering air leaks, late ignition or valve timing, and a number of other problems. Fig. 32 Proper information is vital, so always have a Chilton Total Car Care manual handy

Fig. 33 Two styles of oil drain pan. The screw-in type on top is more accurate and is easier to use, but is more expensive.

Fig. 34 A variety of tools used for spark plug installation and timing adjustment.

TIMING LIGHTS

There are two basic kinds of timing lights- DC powered timing lights, which operate from your vehicle's battery, and AC powered timing lights, which operate on 110 volt house current. Of the two, the DC light is preferable because it produces more light to see the timing marks in bright daylight.

Regardless of what kind is used, the light normally connects in series with the No. 1 spark plug using an adapter. Models that are more expensive sometimes use an inductive pickup, which simply clamps around the plug wire and senses firing impulses. Inexpensive models use alligator clips; one clamps onto the connection between the plug and the plug wire, and the others clamp onto the vehicle battery terminals.

Some timing lights will not work on electronic ignition systems, so unless you still own a vehicle equipped with points, check to make sure the timing light you buy will work.

The biggest problem you will probably have when using a timing light is trying to see the timing marks on the crankshaft pulley. Before you time the engine, mark the appropriate timing indicators with fluorescent paint or chalk. Stay out of direct sunlight when you time the engine and buy a timing light with a xenon light, not a neon light. Timing lights that use a xenon tube provide a much brighter flash than those that use a neon tube do. Fig. 35 A modern electronic timing light. Note the inductive pick-up clamp.

TACHOMETER

You're not going to have much use for the dwell function of a dwell tachometer on late-model vehicles as it is controlled by the computer and is not adjustable. However, if you need to set the base idle speed, and it is adjustable, the tachometer will provide more accuracy than one on your instrument cluster. You don't need one of those gigantic analyzers to set the rpm on your vehicle. Prices range from less than $50$100 and more. Make sure you get a dwell-tach or tach that is compatible with your vehicle's ignition system.

Dwell-tachs are simple to hook up. Some dwell-tachs are powered by the circuit being tested, some operate off the vehicle battery, and some have their own power source. Electronic ignition systems have specific connection procedures and you'll have to check with your dealer to determine the tach hook-up.

There are several Multi-Meter/Engine Analyzers on the market which provide the functions of a Multi Meter and a Engine Analyzers (Dwell & Tach). Fig. 36 Typical aftermarket dwell tachometer- used to check dwell on old point type ignition, and RPM on point and electronic ignition systems.

Electrical and Diagnostic Tools

JUMPER WIRES

Never use jumper wires made from a thinner gauge wire than the circuit being tested. If the jumper wire is of too small a gauge, it may overheat and possibly melt. Never use jumpers to bypass high resistance loads in a circuit. Bypassing resistances, in effect, creates a short circuit. This may, in turn, cause damage and fire. Jumper wires should only be used to bypass lengths of wire.

Jumper wires are simple, yet extremely valuable, pieces of test equipment. They are basically test wires which are used to bypass sections of a circuit. Although jumper wires can be purchased, they are usually fabricated from lengths of standard automotive wire and whatever type of connector (alligator clip, spade connector or pin connector) that is required for the particular application being tested. In cramped, hard-to-reach areas, it is advisable to have insulated boots over the jumper wire terminals in order to prevent accidental grounding. It is also advisable to include a standard automotive fuse in any jumper wire. This is commonly referred to as a "fused jumper". By inserting an in-line fuse holder between a set of test leads, a fused jumper wire can be used for bypassing open circuits. Use a 5 amp fuse to provide protection against voltage spikes.

Jumper wires are used primarily to locate open electrical circuits, on either the ground (-) side of the circuit or on the power (+) side. If an electrical component fails to operate, connect the jumper wire between the component and a good ground. If the component operates only with the jumper installed, the ground circuit is open. If the ground circuit is good, but the component does not operate, the circuit between the power feed and component may be open. By moving the jumper wire successively back from the component toward the power source, you can isolate the area of the circuit where the open is located. When the component stops functioning, or the power is cut off, the open is in the segment of wire between the jumper and the point previously tested.

You can sometimes connect the jumper wire directly from the battery to the "hot" terminal of the component, but first make sure the component uses 12 volts in operation. Some electrical components, such as fuel injectors, are designed to operate on about 4 volts, and running 12 volts directly to these components will cause damage.

TEST LIGHTS

The test light is used to check circuits and components while electrical current is flowing through them. It is used for voltage and ground tests. To use a 12 volt test light, connect the ground clip to a good ground and probe wherever necessary with the pick. The test light will illuminate when voltage is detected. This does not necessarily mean that 12 volts (or any particular amount of voltage) is present; it only means that some voltage is present. It is advisable before using the test light to touch its ground clip and probe across the battery posts or terminals to make sure the light is operating properly.

Do not use a test light to probe ignition spark plug or coil wires. Never use a pick-type test light to probe wiring on computer controlled systems unless specifically instructed to do so. Any wire insulation that is pierced by the test light probe is a good candidate for failure. Most vehicle manufactures recommend against this, some also recommend against back-probing. Back-probing is where the tip of the probe is forced into the back of the connector. Refer to the specific vehicle manufacturers for recommendations.

Like the jumper wire, the 12 volt test light is used to isolate opens in circuits. But, whereas the jumper wire is used to bypass the open to operate the load, the 12 volt test light is used to locate the presence of voltage in a circuit. If the test light illuminates, there is power up to that point in the circuit; if the test light does not illuminate, there is an open circuit (no power). Move the test light in successive steps back toward the power source until the light in the handle illuminates. The open is then between the probe and a point which was previously probed.
The self-powered test light is similar in design to the 12 volt test light, but contains a battery in the handle. It is most often used in place of a multimeter to check for open or short circuits when power is isolated from the circuit (continuity test).

The battery in a self-powered test light does not provide much current. A weak battery may not provide enough power to illuminate the test light even when a complete circuit is made (especially if there is high resistance in the circuit). Always make sure that the test battery is strong. To check the battery, briefly touch the ground clip to the probe; if the light glows brightly, the battery is strong enough for testing.

A self-powered test light should not be used on any computer controlled system or component. Even the small amount of electricity transmitted by the test light is enough to damage many electronic automotive components. Fig. 37 Test lights are simple to use, however check manufacturers recommendations before probing any wires or connectors.

MULTIMETERS

Multimeters are an extremely useful tool for troubleshooting electrical problems. They can be purchased in either analog or digital form and have a price range to suit any budget. A multimeter is a voltmeter, ammeter and ohmmeter (along with other features) combined into one instrument. It is often used when testing solid state circuits because of its high input impedance (usually 10 megaohms or more). A brief description of the multimeter main test functions follows: Voltmeter- the voltmeter is used to measure voltage at any point in a circuit, or to measure the voltage drop across any part of a circuit. Voltmeters usually have various scales and a selector switch to allow the reading of different voltage ranges. The voltmeter has a positive and a negative lead. To avoid damage to the meter, always connect the negative lead to the negative (-) side of the circuit (to ground or nearest the ground side of the circuit) and connect the positive lead to the positive (+) side of the circuit (to the power source or the nearest power source). Note that the negative voltmeter lead will always be black and that the positive voltmeter will always be some color other than black (usually red). Ohmmeter- the ohmmeter is designed to read resistance (measured in ohms) in a circuit or component. All ohmmeters will have a selector switch which permits the measurement of different ranges of resistance (usually the selector switch allows the multiplication of the meter reading by 10, 100, 1,000 and 10,000). Since the meters are powered by an internal battery, the ohmmeter can be used as a self-powered test light. When the ohmmeter is connected, current from the ohmmeter flows through the circuit or component being tested. Since the ohmmeter's internal resistance and voltage are known values, the amount of current flow through the meter depends on the resistance of the circuit or component being tested.

The ohmmeter can also be used to perform a continuity test for suspected open circuits. In using the meter for making continuity checks, do not be concerned with the actual resistance readings. Zero resistance, or any ohm reading, indicates continuity in the circuit. Infinite resistance indicates an opening in the circuit. A high resistance reading where there should be none indicates a problem in the circuit. Checks for short circuits are made in the same manner as checks for open circuits, except that the circuit must be isolated from both power and normal ground. Infinite resistance indicates no continuity to ground, while zero resistance indicates a dead short to ground.

Never use an ohmmeter to check the resistance of a component or wire while there is voltage applied to the circuit. The voltage could severely damage the meter.

Ammeter- an ammeter measures the amount of current flowing through a circuit in units called amperes or amps. At normal operating voltage, most circuits have a characteristic amount of amperes, called "current draw" which can be measured using an ammeter. By referring to a specified current draw rating, then measuring the amperes and comparing the two values, one can determine what is happening within the circuit to aid in diagnosis. An open circuit, for example, will not allow any current to flow, so the ammeter reading will be zero. A damaged component or circuit will have an increased current draw, so the reading will be high.
The ammeter is always connected in series with the circuit being tested. All of the current that normally flows through the circuit must also flow through the ammeter; if there is any other path for the current to follow, the ammeter reading will not be accurate. The ammeter itself has very little resistance to current flow and, therefore, will not affect the circuit, but it will measure current draw only when the circuit is closed and electricity is flowing. Excessive current draw can blow fuses and drain the battery, while a reduced current draw can cause motors to run slowly, lights to dim and other components to not operate properly. Fig. 38 Combination Multi-Meter and Engine Analyzer makes these the most important diagnostic tools you own. Pro model on right has inductive pick-up

SCAN TOOLS

All late-model vehicles utilize computer modules to monitor and control the functions of on-board systems. These modules are known by many names such as Engine Control Unit (ECU), Engine Control Module (ECM), Powertrain Control Module (PCM) and Vehicle Control Module (VCM) just to name a few. When problems occur in control circuits, these modules record a diagnostic trouble code which can be used to help solve the problem. Over the years, there have been many different types of systems, each with their own unique way of retrieving these codes. On a good number of the older systems, the stored codes were flashed on various trouble lights (found in the dashboard) once a small jumper wire was placed across the proper diagnostic terminals. However the use of a hand-held scan tool was still preferred for these systems.

For some models produced during the 1995 model year and on almost every single 1996 and later model, a new form of trouble codes was developed which required the use of a scan tool. On Board Diagnostic-II (OBD-II) compliant vehicles use a 5 digit, alpha-numeric code which would be difficult or impossible to read using a flashing light, therefore trouble code reading on an OBD-II compliant requires a scan tool.

There are many manufacturers of these tools, but a purchaser must be certain that the tool is proper for the intended use. If you own a scan type tool, it probably came with comprehensive instructions on proper use. Be sure to follow the instructions that came with your unit

The scan tool allows any stored codes to be read from the computer module memory. The tool also allows the operator to view the data being sent to the computer control module while the engine is running. This ability has obvious diagnostic advantages; the use of the scan tool is frequently required for component testing. The scan tool makes collecting information easier; the data must be correctly interpreted by an operator familiar with the system.

An example of the usefulness of the scan tool may be seen in the case of a temperature sensor which has changed its electrical characteristics. The computer module is reacting to an apparently warmer engine (causing a driveability problem), but the sensor's voltage has not changed enough to set a fault code. Connecting the scan tool, the voltage signal being sent to the module may be viewed; comparison to normal values or a known good vehicle reveals the problem quickly. Fig. 39 Typical aftermarket scan tool used to access diagnostic codes from the Electronic Control Module.

Fig. 40 This Auto Xray® scan tool uses manufacturer specific cables to interface with the various connectors.

SOLDERING GUN

Soldering is a quick, efficient method of joining metals permanently. Everyone who has the occasion to make electrical repairs should know how to solder. Electrical connections that are soldered are far less likely to come apart and will conduct electricity far better than connections that are only "pig-tailed" together.

The most popular (and preferred) method of soldering is with an electric soldering gun. Soldering irons are available in many sizes and wattage ratings. Irons with high wattage ratings deliver higher temperatures and recover lost heat faster. A small soldering iron rated for no more than 40 watts is recommended for home use, especially on electrical projects where excess heat can damage the components being soldered.

There are three ingredients necessary for successful soldering- proper flux, good solder and sufficient heat.

Flux

A soldering flux is necessary to clean the metal of tarnish, prepare it for soldering and to enable the solder to spread into tiny crevices. When soldering electrical work, always use a resin flux or resin core solder, which is non-corrosive and will not attract moisture once the job is finished. Other types of flux (acid-core) will leave a residue that will attract moisture, causing the wires to corrode.

Good Solder

Tin is a unique metal with a low melting point. In a molten state, it dissolves and alloys easily with many metals. Solder is made by mixing tin (which is very expensive) with lead (which is very inexpensive). The most common proportions are 40/60, 50/50 and 60/40, the percentage of tin always being listed first. Low-priced solders often contain less tin, making them very difficult for a beginner to use because more heat is required to melt the solder. A common solder is 40/60 which is well suited for all-around general use, but 60/40 melts easier, has more tin for a better joint and is preferred for electrical work.

Sufficient Heat

Successful soldering requires that the metals to be joined be heated to a temperature that will melt the solder, usually somewhere around 360–460°F (182–237°C), depending on the tin content of the solder. Contrary to popular belief, the purpose of the soldering iron is not to melt the solder itself, but to heat the parts being soldered to a temperature high enough to melt solder when it is touched to the work. Melting flux-cored solder on the soldering iron will usually destroy the effectiveness of the flux. Fig. 41 These are several types of soldering tools and guns

How to Solder

Soldering tips are made of copper for good heat conductance, but must be "tinned" regularly for quick transference of heat to the project and to prevent the solder from sticking to the iron. To "tin" the iron, simply heat it and touch flux-cored solder to the tip; the solder will flow over the tip. Wipe the excess off with a rag.
After some use, the tip may become pitted. If so, dress the tip smooth with a fine file and "tin" the tip again.
An old saying holds that "metals well-cleaned are half soldered". Flux-cored solder will remove oxides, but rust, bits of insulation and oil or grease must be removed with a wire brush or emery cloth.
For maximum strength in soldered parts, the joint must start off clean and tight. Weak joints will result in gaps too wide for the solder to bridge.
If a separate soldering flux is used, it should be brushed or swabbed on only those areas that are to be soldered. Most solder contains a core of flux and separate fluxing is unnecessary.
Hold the work to be soldered firmly. It is best to solder on a wooden board, because a metal vise will only rob the piece to be soldered of heat and make it difficult to melt solder. Hold the soldering tip with the broadest face against the work to be soldered. Apply solder under the tip close to the work. Apply enough solder to give a heavy film between the iron and piece being soldered, moving slowly and making sure the solder melts properly. Keep the work level or the solder will run to the lowest part, and favor the thicker parts, because these require more heat to melt the solder. If the soldering tip overheats, (the solder coating on the face of the tip burns up). The tip should be re-tinned.
Once the soldering is completed, let the soldered joint stand until cool.

Fig. 42 If necessary, dress a pitted tip with a fine file

Fig. 43 Tinning the soldering iron

Fig. 44 Wipe the excess solder from the iron while hot

Fig. 45 The correct method of soldering. Let the heat transferred to the work melt the solder

Repair Guide: Tools and Supplies (Part 1 of 3)

2008-03-10T12:10:00.000-07:00

Analyze Your Needs

Nearly everybody needs some tools, whether they're just for fixing the kitchen sink, or overhauling the engine in the family vehicle. As far as vehicle repairs go, pliers and a can of oil aren't going to get you very far down the path of do-it-yourself service. However, you don't have to equip your garage like the local service station either. Somewhere between these two extremes, there's a level that suits the average do-it-yourselfer. Just where that point is depends on your needs, your ability and your interest. The trick is to match your tools and equipment to the jobs you're willing and able to tackle.

Choose Your Own Level

To sort things out in an orderly manner, think about your repair work in three levels: basic, average and advanced. Before you purchase any tools, sit down and determine your present level of mechanical expertise. After you have determined that (be honest), determine just how far you intend to progress as an amateur mechanic. Knowing what you can and/or will do in the way of automotive repairs is the most important step you can take. Obviously, if all you ever intend to do is to change the oil and the plugs now and then, you won't need very many tools. If, however, you plan some extensive repair work, you're going to end up with a complete collection of tools.

Once you have determined your level of mechanical involvement, evaluate your tool purchases on a "must have" and a "nice-to-have" basis.

BASIC LEVEL

At a basic level of involvement, you'll probably do such things as check the coolant, oil and other fluid levels, and change the oil and filter. You also might perform basic maintenance, keep an eye on the tire pressures, keep the vehicle waxed and polished, and perhaps perform some minor body touch-up.

AVERAGE LEVEL

The average level involvement will probably include replacing belts and hoses, replacing shocks, and engine tune-up.

ADVANCED LEVEL

At the advanced level, you might dig deeply enough to re-line the brakes, check compression, install a trailer hitch, replace a bad muffler, or repair body damage.
The advanced level would be a good choice for someone getting into the automotive service profession.

Basic Tools

After you've determined your level of mechanical expertise, and how far you want to progress as an amateur mechanic, you have to buy some tools. No matter what level you have decided on, there are some tools you must have. These include pliers, open and box end wrenches, a ratchet and sockets, various types of screwdrivers, some punches and chisels, a hammer and hacksaw.

Fig.1 All but the most basic procedures will require an assortment of ratchets.

Figure 2. Trouble lights come in a variety of configurations. The Incandescent model on the left is the old stand-by, however the florescent work light remains cool with use and is excellent for working in close quarters.

It will be worth your while to buy quality hand tools. You can buy tools in supermarkets but they'll probably only cause you grief. Stick to the name-brand tools and you won't go wrong. Manufacturers like Craftsman, Mac, Snap-On, SK etc. make top-quality tools that will last a lifetime. Many name-brand tools are also sold with a "no questions" guarantee. If you break it, just take it back and it will be replaced, no questions asked. So, buy your tools from a reputable tool manufacturer. You'll pay a little more, but it's worth it to avoid skinned knuckles and rounded-off bolts.

METRIC OR SAE?

See Figures 3 and 4
There are two different types of fasteners used on vehicles today, metric and SAE. While SAE is actually the abbreviation for Society of Automotive Engineers, it is the common term frequently used to describe U.S. standard or fractional fasteners.

Deciding whether you needed metric or SAE tools did not use to be a problem. Years ago, American made vehicles used SAE fasteners, and import vehicles used metric. These days with components for American vehicles being engineered in various places using both SAE and Metric measurements you may find your domestic vehicle has both types of fasteners used. If you own an import vehicle, more than likely you'll need metric tools. Likewise, if you have a late-model American vehicle, you might need some, or all metric tools.

Common metric fasteners and the wrench size required are listed in the following chart.

Figure 3

SAE/METRIC WRENCH SIZES
Many import cars and a few American cars use metric wrench sizes. In a few cases, an SAE wrench or socket may appear to fit a metric bolt, but a chewed up bolt and skinned knuckles will be the only result. It's always best to use the right size wrench. The following chart compares common SAE and metric wrench sizes.
SAE Wrench Sizes		Metric Wrench Sizes
INCHES	DECIMAL	DECIMAL	MILLIMETERS
1/8"	0.125	0.118	3mm
3/16"	0.187	0.157	4mm
1/4"	0.250	0.236	6mm
5/16"	0.312	0.354	9mm
3/8"	0.375	0.394	l0mm
7/16"	0.437	0.472	12mm
1/2"	0.500	0.512	13mm
9/16"	0.562	0.590	15mm
5/8"	0.625	0.630	16mm
11/16"	0.687	0.709	18mm
3/4"	0.750	0.748	19mm
13/16"	0.812	0.787	20mm
7/8"	0.875	0.866	22mm
15/16"	0.937	0.945	24mm
1"	1.000	0.984	25mm

Before you buy any tools, check with your dealer to determine just what kind of fasteners your vehicle has. Some American vehicles are metric, while some are part metric and part SAE. Also, keep in mind that some import vehicles (such as Volvo) utilize some SAE fasteners.

While there are some points of interchange between the metric and inch sizes, it's not a good idea to use metric wrenches on SAE fasteners and vice versa. In an emergency, you can use anything that will fit, but prolonged use will only ruin the fastener.

Figure 4

Fastener Size (Millimeters)	Required Wrench
4 x .7	7 mm
5 x .8	8 mm
6.3 x 1	10 mm
8 x 1.25	13 mm
10 x 1.5	15 mm
12 x 1.75	18 mm
14 x 2	21 mm
16 x 2	24 mm

PLIERS

See Figures 5 and 6
Pliers come in a variety of shapes and sizes and you'll probably need at least three different kinds for a beginning tool kit. The regular slip-joint kind that everyone is familiar with is an absolute necessity. Long-nosed or needle-nosed pliers should be in everyone's tool kit also. The number of jobs these two tools are good for is endless. Locking pliers (commonly called Vise Grips®) are so useful; you'll wonder how you ever got along without them. A good pair of cutting pliers is necessary for any kind of wiring job.

Eventually, you may want to add specialized pliers. There are pointed-tip pliers for spreading lock rings and hooked pliers for removing brake springs. Some pliers have a groove in the end to compress the wire hose clamps used on many radiator hoses, although these can be made from a pair of old pliers by filing a groove in the end.

Wire strippers are also handy for electrical work. Most have special grooves for stripping various gauges of wire without cutting the wire inside. Fig. 5. Pliers come in all shapes and sizes. Locking pliers are handy for removing old rusted parts.

Fig. 6. Wire strippers and cutting pliers are handy for doing electrical work

HAMMERS

See Figure 7
Hammers come in four basic types- machinist's (ball peen), plastic (soft faced), sledge, and dead blow. The basic hammer for a mechanic is the ball peen. If you already have a good claw hammer, keep it with your carpentry tools, it won't do for automotive use.

If you are going to buy a hammer, get one with an 8- or 12-ounce head that is drop forged and heat-treated. The handle of a quality hammer will be hickory, ash or fiberglass.

A soft faced mallet is useful in situations where less force is required, rubber mallets are good for installing snap-on hubcaps, and other jobs where you don't want to mar the surface. Fig. 7. A variety of hammers are useful for different applications- Ball peen, soft faced, sledges, and dead blow.

SCREWDRIVERS

See Figures 8, 9, 10 and 11
Screwdrivers are another must for anyone planning to do any sort of automobile repair work. There are two general types of screwdrivers- Phillips head and slot head screwdrivers. Keep in mind that these types of screwdrivers come in various sizes, so just because you have a slotted head screwdriver, and a Phillips head doesn't mean you're going to be able to fit every screw you come across. Screwdrivers are often sold in sets containing all the common types.

Other specialized screwdrivers (Torx® and Reed Prince tips, clutch head, butterfly) are only useful if your vehicle uses screws that they will fit. The best practice is to acquire them as necessary. If you are working on a screw in an awkward location, a magnetic screwdriver is indispensable. There are also locking screwdrivers known as screw starters that are handy for this operation. Many of the magnetic screwdrivers have interchangeable bits for various types of screw heads. Fig. 8. Slot head screwdrivers come in assorted sizes and lengths

Fig. 9. Phillips screwdrivers also come in assorted sizes and lengths, these are more common in automotive use

Fig. 10 Screwdrivers are NOT made for prying! Use only a prybar for prying.

Fig. 11 Keep your screwdriver tips in good shape. They should fit in the screw slot as shown in "A". If they look like the ones in "B" they need to be ground or replaced.

WRENCHES

See Figures 12 and 13
Wrenches come in two kinds- open end and box end. Both kinds are necessary for any sort of tool kit. The box end wrenches are ordinarily of the twelve-point type, and offer a better grip than the open-end type, although obviously they cannot be used for some jobs.

Wrench offset is a consideration when buying wrenches. The head may be angled to make access to some bolts or nuts easier. Standard offset is 15°–30°, but most wrenches are available from straight (0°) to right angle (90°) offsets. Many tool manufacturers offer combination wrenches, which are an open-end wrench on one end and a box end on the other. Box end wrenches are also available in ratcheting models, although their usefulness is limited for the amateur mechanic.

For fuel and brake line work, a special type of wrench known as a line wrench is available. It is nothing more than a box end wrench with one of the flats cut out so that it can be slipped over the line.

Adjustable open wrenches are also very handy, but the cheap kinds are no good at all, since they won't hold they're setting. Good quality adjustable wrenches are available in various lengths, and you should have at least one. Fig. 12 Combination wrenches come in both metric and SAE sizes

Fig. 13 When you are using an open end wrench, use the correct size and position it properly on the flats of the nut or bolt.

ALLEN AND STAR WRENCHES

See Figures 14 and 15
Allen and star (Torx®) wrenches are required more and more to work on vehicles. Allen wrenches are hexagonal and Torx® bits are multi-serrated inserts that fit inside a bolt or screw head rather than lining around the outside of the head. They can be L-shaped tools with their own handles or are available to fit a ratchet handle Fig. 14 Torx® drivers come in both ratchet and screwdriver type

Fig. 15 Allen head wrenches and sockets come in both metric and SAE

RATCHET AND SOCKETS

See Figures 16 and 17
A ratchet and socket set will probably be one of the most expensive purchases you make in assembling a basic tool kit. Ratchet drives come in three common sizes, ½ inch, ³/&sup8; inch and ¼ inch drive. (There is also a ¾ inch drive ratchet, but it is of little use, unless you own a very large vehicle.) When buying a ratchet, pick the size you think you'll use the most. The ¼ inch size is only useful for smaller jobs. The 3/8 inch size is the most popular and useful. Sockets come in six- or twelve-point faces, and in standard and deep lengths.

There are plenty of specialty tools for socket sets. Universal joints allow you to get into tight places, but are frequently hard to maneuver. Adapters let you use different size drive sockets on other ratchet handles. Crowfoot wrenches are simply open-end wrench heads that fit a ratchet drive. Speeder handles; super-deep sockets, magnetic inserts, and screwdriver bits are all nice to have, if you have a use for them. If not, don't bother cluttering up your toolbox. Spark plugs require a deep socket, while the standard length is suitable for most of the other jobs you will encounter. The six-point sockets are heavier and give a better grip, but the twelve-point sockets offer more turning positions for working in tight places.

You can also do yourself a big favor and choose a flexible head ratchet over a regular ratchet. A flex head 3/8 inch drive ratchet with a 6 inch extension will enable you to do most any job you want to do.

The ratchet handle comes in various lengths with a varying number of teeth on the ratchet. If you have a choice, pick the shorter ratchet handle and the one with the most teeth on the ratchet mechanism (most clicks per turn of the handle). This will give you the greatest flexibility to reach tight places and the fewest bruised knuckles. Fig. 16 Common ratchet sets come in ½inch, 3/8 inch, and ¼inch sizes

Fig. 17 Some of the many different types of sockets available
Star, serrated or Torx bit Allen wrenches 1/4" drive 6-point sockets 1/4" drive 12-point sockets 1/2" or 5/8" drive 6-point sockets 1/2" or 5/8" drive 12-point sockets	5/8" (right) and 13/16" (left) spark plug sockets Ratchet drive adaptors Universal joints Universal joint with socket wrench Screwdriver socket bits

TORQUE WRENCH

See Figures 18 and 19
If you plan to do anything more involved than changing the oil, you'll need a torque wrench. The beam-type models are perfectly adequate, although the click-type models are much more precise. Keep in mind that if you're tightening a part that has a torque value given, it's there for a reason. So, use the torque wrench.

Click-type (or breakaway) torque wrenches can be dialed to any desired setting and will automatically release once the setting is reached. These are used mostly by professionals, and are not necessary for the backyard mechanic. The beam-type torque wrench, while not quite as accurate or as fast to use as the click-type, is adequate for most everyday use, and is usually quite inexpensive. When using a torque wrench on any fasteners, keep the socket as straight as possible on the fastener. Trying to torque something on an angle just won't work. Using the wrench on an angle will create increased resistance and the result will be an inaccurate reading. Fig. 18 Various styles of torque wrenches are available at your local automotive store

Fig. 19 Common click type torque wrenches are the most popular

Engine Problems Troubleshooting (Part 2)

2008-01-31T11:29:00.000-08:00

Loud exhaust

Description of problem: There is a loud exhaust noise which may be coming from either the front or rear of the vehicle.

Probable Causes:

1. Muffler or exhaust pipe worn out.

2. Exhaust manifold worn out.

Gray smoke from the exhaust

Description of problem: You notice a grayish smoke coming from the exhaust when you start your car. The smoke may still be there after the car is warmed, but it may be less noticeable. The smoke may have a bluish tint to it. This problem normally develops over time, and the amount of smoke indicates the seriousness of the problem.

Probable Causes:

1. Worn piston rings.

2. Worn valve guides.

3. Damaged or worn valve guides.

White smoke or water vapor from the exhaust

Description of problem: You notice a white smoke coming from the exhaust when you start your car. This may be normal if the weather is cold. However, if the smoke continues after the engine is warmed up, there is a problem. This problem normally develops over time, and the amount of smoke indicates the seriousness of the problem.

Probable Causes:

1. Automatic transmission fluid may be entering the intake manifold through vacuum connections.

2. The engine's cylinder head gasket may be bad.

3. The engine's cylinder head may be warped or cracked.

4. The engine's block may be cracked.

Black smoke from the exhaust

Description of problem: You notice black smoke coming from the exhaust when you start your car. The smoke may still be there after the car is warmed, but it may be less noticeable. The smoke may be accompanied by engine idling problems. This problem normally develops over time, and the amount of smoke indicates the seriousness of the problem.

Probable Causes:

1. If you have a carburetor, the carburetor choke may be stuck closed.

2. The fuel injectors may be leaking.

3. The air filter may be clogged.

4. There may be an ignition problem.

Popping noise from exhaust

Description of problem: Whenever you press on the gas pedal, you hear a popping from the exhaust. For the most part, the engine seems to run fine. However, you have noticed your gas mileage has gotten worse. The louder the popping noise, the worse the problem.

Probable Causes:

1. You have a vacuum leak.

2. One or more of your fuel injectors are leaking.

3. There is a hole or leak in the car's exhaust.

The car uses more oil than normal, and there is some smoke from the exhaust

Description of problem: You notice that the oil level is low between oil changes. This did not happen before. It appears that the oil is being burned by the engine because of the smoke in the exhaust. You may also have noticed that the car doesn't have the same amount of power as it once did. This type of problem seems to get worse once it develops.

Probable Causes:

1. The PCV system is not working properly.

2. The engine may have mechanical problems.

3. The engine's valve seals may be worn.

4. The engine's piston rings may be worn.

There is a rotten egg smell coming from the exhaust

Description of problem: Whenever you run the engine and are not moving, you notice an awful smell from the exhaust. The smell is like that of rotten eggs. Not only do you notice this, so does everyone around your car. You may also have noticed that your gas mileage has been worse lately.

Probable Causes:

1. There is a problem with your electronic engine control system.

2. You have an ignition problem.

3. Your fuel pressure regulator is bad.

4. The engine may have mechanical problems.

5. The engine is running too hot.

There is a strong gas smell coming from the exhaust

Description of problem: Whenever you run the engine and are not moving, you notice the smell of gas from the exhaust. The smell can be strong enough to make you think you have a gas leak. Not only do you notice the smell, so does everyone around your car. You may also notice that your gas mileage has been worse lately.

Probable Causes:

1. There is a problem with your electronic engine control system.

2. You have an ignition problem.

3. Your fuel injectors are clogged or dirty.

4. There is an engine mechanical problem.

5. You have a vacuum leak.

6. If you have a carburetor, the choke may be stuck closed.

The car uses more oil than normal, but there is no trace of smoke from the exhaust

Description of problem: You notice that the oil level is low between oil changes. This did not happen before. It doesn't appear that the oil is being burned by the engine because there is not a trace of smoke in the exhaust. You may have also noticed that the car doesn't have the same amount of power it once did. This type of problem seems to get worse once it develops.

Probable Causes:

1. The PCV system is not working properly.

2. The engine may have mechanical problems.

3. The engine's valve seals may be worn.

4. There may be a small oil leak.

The car uses more fuel than normal, and there is a strong gas odor coming from the exhaust

Description of problem: You notice a tank of gas doesn't last as long as it used to. You also smell raw gasoline, especially when you stop the engine. You don't find obvious signs of a gas leak such as puddles under the car. You may have also noticed that the car doesn't have the same amount of power it once did. This type of problem seems to get worse once it develops and can lead to other serious problems such as not starting.

Probable Causes:

1. The fuel lines may have a leak.

2. The engine may have mechanical problems..

3. The fuel pressure regulator may be operating at too high a pressure.

4. The fuel injectors may leak.

5. The gas cap may be faulty.

Engine Problems Troubleshooting (Part 1)

2008-01-31T11:27:00.000-08:00

Engine hesitates

Description of problem: Whenever you push on the accelerator (gas pedal), the car doesn't seem to move like it should or like it did before. You sense a general lack of power and know something is not right. This problem may appear suddenly or get worse over time. You may notice the problem when the engine is hot or cold or when you are low on fuel. A description of when the problem occurs will help to identify the exact cause of the problem.

Probable Causes:

1. You may have a dirty air filter.

2. The spark plugs may be dirty or worn.

3. The spark wires may be bad.

4. There may be some other type of ignition problem.

5. The fuel filter may be clogged.

6. You may have water in the gasoline.

7. If you have a carburetor, you may have a bad accelerator pump or power circuit.

8. Your catalytic converter may be clogged.

The engine surges or misfires while moving

Description of problem: The engine seems to start fine and will normally accelerate fine. However, once you try to keep a steady speed, the engine sputters and runs rough. You may notice that the engine runs differently when it is cold or warm. This type of problem normally is slow to develop but gets worse the longer you drive the car.

Probable Causes:

1. If you have a carburetor, the choke may not be set properly, or the choke may not be working correctly.

2. The engine may be running too hot.

3. The fuel pressure regulator may be operating at too low of a pressure.

4. The ignition timing may be set wrong.

5. There may be some type of ignition problem.

6. There may be a fault in the computerized engine control system.

7. The fuel filter may be partially clogged.

8. The torque converter in the transmission may not be locking at the right time, or it may be slipping.

9. There may be a vacuum leak.

10. The engine may have mechanical problems.

11. The EGR valve may be stuck open.

12. The drive axles may be loose or worn.

13. The fuel injectors may be dirty.

A hissing sound is heard from the engine

Description of problem: The engine may or may not seem to run fine. Normally, the hissing noise becomes apparent soon after the driver notices that the engine is not running properly. This problem can occur suddenly.

Probable Causes:

1. The engine is overheating.

2. The exhaust system and/or catalytic converter is plugged.

3. A vacuum line is disconnected.

4. A vacuum device is leaking

Whirring from the engine that gets worse as engine speed increases

Description of problem: Although the whirring noise is evident at all engine speeds, it is the change in volume as engine speed increases that makes the noise most noticeable. This type of problem can be caused by many things. Some causes gradually develop, while others occur suddenly.

Probable Causes:

1. Low power steering fluid

2. The alternator bearings are bad.

3. A bad water pump.

4. A bad power steering pump.

5. A bad air conditioning compressor.

Smoke is coming from under the hood

Description of problem: Sometimes you will only see the smoke when you start your car or when you stop at a traffic light or stop sign. The smoke may be accompanied by engine idling problems. This is a problem that should not be ignored as it may be an indication of a serious and dangerous condition. The cause of the problem is best identified by the color, smell, and amount of smoke. Pay close attention to this. This problem may develop over time and the amount of smoke indicates the seriousness of the problem.

Probable Causes:

1. If the smoke has an oily smell, there is an oil leak.

2. If the smoke is white, there is probably an anti-freeze (engine coolant) leak.

3. If the smoke is blue or black and has a strong acrid smell, there is probably an electrical problem, and wires are burning.

Engine backfires when you press on the gas pedal

Description of problem: Basically, your engine is a mess. Every time you press on the gas pedal, the engine pops back at you. Sometimes the noise is loud, other times it is rather soft. This noise may result in an under hood fire, so don't ignore it.

Probable Causes:

1. Your camshaft timing belt or chain may have slipped

2. Your ignition timing needs adjusting.

3. There is a serious engine problem.

4. Your spark plug wires are placed on the wrong spark plugs.

Engine hesitates, and a popping is heard from the engine

Description of problem: Whenever you push on the accelerator (gas pedal), the car doesn't seem to move like it should or like it did before. You sense a general lack of power and know something is not right. The popping noise convinces you that something really isn't right. The noise only happens when you press on the gas pedal. This problem may appear suddenly or get worse over time. You may notice the problem when the engine is hot or cold or when you are low on fuel. A description of when the problem occurs will help to identify the exact cause of the problem.

Probable Causes:

1. You may have a dirty air filter.

2. The spark wires may be bad.

3. There may be some other type of ignition problem.

4. There may be a mechanical problem in the engine.

Engine makes a clicking noise when idling

Description of problem: As the engine is idling, you hear a clicking noise coming from the engine. You don't notice the click when you are moving or when you increase the speed of the engine. The problem seems to get worse (noisier) when the engine is warm. The clicking is also getting more noticeable every day.

Probable Causes:

1. Your valves need adjusting.

2. The engine is low on oil.

3. The engine's oil pressure is low.

Engine makes a ticking noise

Description of problem: As soon as you start the engine, you hear a ticking noise from the engine. It sounds like a loud clock. The speed of the noise increases with an increase in engine speed. In fact, when you reach a particular speed, the noise is occurring so fast it seems that it is gone.

Probable Causes:

1. The valves in your engine need to be adjusted.

2. There is a lot of sludge in your engine which is stopping oil from circulating properly.

3. The engine's valve lifters are collapsed.

4. One or more of the engine's valves are stuck.

There is a rattling noise from the engine when you accelerate

Description of problem: Your car seems to run fine at all times. You notice nothing unusual except when you press on the gas pedal to accelerate or to go up a hill. Then the engine rattles like something is loose inside of it. Normally, this problem begins slowly and gets worse.

Probable Causes:

1. Your ignition timing needs adjusting.

2. The engine is overheating.

3. You have a loose vacuum hose on the engine.

4. You bought low-octane fuel even though your owner's manual says to only use high-octane fuel.

5. There is an excessive amount of carbon built up in your engine.

6. You have a problem with the electronic engine control system.

The engine surges or misfires while moving

Description of problem: The engine seems to start fine and will normally accelerate fine. However, once you try to keep a steady speed, the engine sputters and runs rough. You may notice that the engine runs differently when it is cold or warm. This type of problem normally is slow to develop but gets worse the longer you drive the car.

Probable Causes:

1. If you have a carburetor, the choke may not be set properly, or the choke may not be working correctly.

2. The engine may be running too hot.

3. The fuel pressure regulator may be operating at too low of a pressure.

4. The ignition timing may be set wrong.

5. There may be some type of ignition problem.

6. There may be a fault in the computerized engine control system.

7. The fuel filter may be partially clogged.

8. The torque converter in the transmission may not be locking at the right time, or it may be slipping.

9. There may be a vacuum leak.

10. The engine may have mechanical problems.

11. The EGR valve may be stuck open.

12. The drive axles may be loose or worn.

13. The fuel injectors may be dirty.

Clunking from the engine that worsens when engine speed increases

Description of problem: When you press on the gas pedal, the engine makes a clunking noise. The noise increases as you press harder on the gas pedal. The noise is there whether you are in gear or in neutral. Sometimes the noise is not noticeable when you are letting the engine idle but occurs as soon as you press on the gas pedal. Normally, the problem begins gradually, but the noise may go unnoticed. As the problem worsens, the noise gets louder.

Probable Causes:

1. Worn engine bearings.

2. Broken engine parts.

3. Loose or missing flywheel mounting bolts.

The car uses more oil than normal, and there are oil puddles under the car after it has been parked

Description of problem: You notice that the oil level is low between oil changes. You also notice puddles of oil under the car. It seems obvious that the loss of oil is due to oil leaks. Sometimes when you stop at a light or stop sign, smoke comes from under the hood. To identify the exact cause of the problem, it is best to look at the source of the oil leak. In addition to having the oil leaks repaired, you should make sure the engine always has the proper oil level. You may have also noticed that the car doesn't have the same amount of power as it once did. This type of problem seems to get worse once it develops.

Probable Causes:

1. The PCV system is not working properly.

2. The engine may have mechanical problems.

3. The engine's seals may be damaged.

4. The oil filter may not be tightened properly.

The engine quickly overheats

Description of problem: The engine seems to run fine but gets very hot shortly after you start it. This problem normally occurs after only five minutes of running or after traveling about a mile. You may also notice steam coming from the hood or smell something hot. This type of problem is slow to develop but gets worse the longer you drive. Once the engine begins to get too hot, turn it off or further damage will occur.

Probable Causes:

1. The engine's coolant level may be too low.

2. The engine's drive belts may be broken or slipping.

3. The electric cooling fan may not be coming on.

4. The ignition timing may be set wrong.

5. There may be a vacuum leak.

6. The engine may have mechanical problems.

7. The engine's thermostat may be stuck closed.

8. There may be a leak in the cooling system.

9. The engine's head gasket may be leaking.

The engine overheats

Description of problem: The engine seems to run fine but gets very hot after it has been driven. This problem normally occurs after driving some distance or while pulling a heavy load. You may also notice steam coming from the hood or smell something hot. This type of problem is slow to develop but gets worse the longer you drive it. Once the engine begins to get too hot, turn it off or further damage will occur.

Probable Causes:

1. The engine's coolant level may be too low.

2. The engine's drive belts may be broken or slipping.

3. The electric cooling fan may not be coming on.

4. The ignition timing may be set wrong.

5. There may be a vacuum leak.

6. The engine may have mechanical problems.

7. You have been pushing the car too hard and making it work too hard.

8. There may be a leak in the cooling system.

9. The engine's head gasket may be leaking.

10. The radiator may be clogged.

Your engine or oil light comes on while driving

Description of problem: The oil light may be marked engine. If this is the case, this light and warning system monitors the water temperature of the engine in addition to the oil. If this light stays on regardless of how fast you run the engine, there is a serious problem. Sometimes the light will come on when the engine is idling and go out when the engine's speed is increased. In most cases, this problem becomes more evident as the problem gets worse.

Probable Causes:

1. The engine has lost oil pressure or has low oil pressure (this is a serious problem that should be repaired at once).

2. The oil pressure sending unit is bad.

3. The engine is extremely low on oil.

4. The engine is overheating.

Your check engine or service engine light comes on or stays on

Description of problem: This is an area of much confusion since most manufacturers, until recently, have called this light by different names. This light also adds to confusion because the manufacturers have different systems that are monitored by this light circuit. In most cases, this warning light is part of the electronic engine control circuit. When the light comes on, it means that the car's computer has detected something wrong in the control system. The lamp remains lit until the problem is corrected. However on some systems, this light simply means there is a problem. The check engine or service engine light may suddenly come on and remain on, or it may come on and go out after a period of time.

Probable Causes:

1. The engine's computer has detected a problem in the system.

2. The engine has a serious problem that should be repaired at once.

3. The engine's oil pressure is exteremely low.

4. The engine is overheating.

Engine doesn't want to increase its speed

Description of problem: Whenever you push on the accelerator (gas pedal), the engine seems to slow down and sometimes it stalls. In order to increase the speed of the engine, you must very slowly press down on the gas pedal. Even then, the car doesn't seem to move like it should, and you sense a general lack of power. This problem may appear suddenly or get worse over time. You may notice the problem when the engine is hot or cold or when you are low on fuel. A description of when the problem occurs will help to identify the exact cause of the problem.

Probable Causes:

1. You may have a dirty air filter.

2. The fuel filter may be clogged with dirt.

3. The fuel pump may be worn.

4. The ignition timing may be wrong.

5. You may have water in the gasoline.

6. Your catalytic converter may be plugged.

Engine doesn't have its normal amount of power

Description of problem: Whenever you push on the accelerator (gas pedal), the car doesn't seem to move like it should or like it did before. You sense a general lack of power and know something is not right. There are no unusual noises or vibrations, but the engine just isn't performing well. The problem seems to be getting increasingly worse over time, although you did not notice when it first started.

Probable Causes:

1. You may have a dirty air filter.

2. The spark plugs and/or wires may be bad.

3. There may be some other type of ignition problem.

4. There may be a mechanical problem in the engine.

5. The catalytic converter may be plugged.

6. The exhaust system may be plugged due to dirt or damage.

7. The fuel filter may be clogged.

The engine will not idle smoothly, or it stalls during idle when the engine is cold.

Description of problem: When the engine is cold and you take your foot off the gas pedal, the engine runs very rough and may even stall. When you run the engine at higher speeds, it seems to run fine. This problem may get worse over time, or it may appear suddenly.

Probable Causes:

1. If you have a carburetor, the choke may not be set properly, or the choke is not working correctly.

2. There may be a vacuum leak in the intake system.

3. The idle speed may be set wrong.

4. There may be some type of ignition problem.

5. The ignition timing may be set wrong.

6. There may be a fault in the computerized engine control system.

7. The EGR valve may be defective.

8. There may be a mechanical problem in the engine.

9. The fuel injectors may be dirty.

The engine will not idle smoothly, or it stalls during idle when the engine is warm

Description of problem: When the engine is warm or hot and you take your foot off the gas pedal, the engine runs very rough and may even stall. When you run the engine at higher speeds, it seems to run fine. This problem may get worse over time or it may suddenly appear.

Probable Causes:

1. If you have a carburetor, the choke may not be set properly, or the choke is not working correctly.

2. There may be a vacuum leak in the intake system.

3. The fuel pressure regulator may be operating at too low of a pressure.

4. The idle speed may be set wrong.

5. There may be some type of ignition problem.

6. There may be a fault in the computerized engine control system.

7. The EGR valve may be defective.

8. There may be a mechanical problem in the engine.

9. The fuel injectors may be dirty.

The engine idles too fast

Description of problem: After you start the engine and it has run long enough to be warm, the engine seems to be racing. You especially notice this when you stop at a light or a stop sign and must push hard on the brake pedal to keep the car from moving. This problem normally happens without warning.

Probable Causes:

1. If you have a carburetor, the choke may not be set properly, or the choke is not working correctly.

2. The engine may be running too hot.

3. The fuel pressure regulator may be operating at too low of a pressure.

4. The ignition timing may be set wrong.

5. There may be some type of ignition problem.

6. There may be a fault in the computerized engine control system.

7. The alternator may not be working properly.

8. There is an air leak in the intake system.

9. You have a bad idle speed control unit.

Car stalls when stopped quickly

Description of problem: You are driving down the road, and everything is fine until you let off the gas pedal and apply the brakes. At this point the engine shakes badly and may even quit running. This is very dangerous as you lose power steering when the engine is not running. This type of problem may occur suddenly.

Probable Causes:

1. An intake system gasket is leaking.

2. The throttle linkage or mechanism needs to be repaired or replaced.

3. There is a problem with the electronic engine control system.

Engine surges while driving at a steady speed.

Description of problem: While driving at a constant speed on a highway, you notice the car seems to buck or jerk. If you press on the gas pedal, the engine smooths out. You only notice this problem when the road is flat and you are trying to keep a steady speed. This problem may occur suddenly and get worse over time.

Probable Causes:

1. Your fuel filter is dirty.

2. Your fuel pump is worn out.

3. The fuel pressure regulator isn't working properly

4. The last tank of fuel you bought was bad gas.

Engine continues to run when you try to turn it off

Description of problem: The car seems to run fine except that it doesn't want to turn right off. After you have driven awhile, you turn the key to stop the engine and it continues to run for a few seconds. At first you notice that this happens once in awhile, and now it happens quite often.

Probable Causes:

1. One or more of your fuel injectors are leaking.

2. The engine's idle is set too high.

3. The ignition timing is set wrong.

Tire talk: Tire Care and Replacement

2008-01-31T09:04:00.000-08:00

There are some easy things you can do to prolong the life of your tires and improve your vehicle's safety.

Keep your tires properly inflated -- correct air pressure is required for good handling and traction, good fuel economy and even wear. The only way to determine proper tire pressure is to use an accurate gauge. Tire pressure should be checked and corrected only when the tires are cold; even a short drive can make your tires too hot for accurate pressure readings. Don?t inflate tires to the maximum pressure printed on the tire -- use the tire pressure recommended in your vehicle?s owners manual or tire information sticker (located in the glove box, on the door post, or inside the fuel door). Remember to check the pressure in your spare tire

Checking Your Tire Pressure
The main reason you should care about tire pressure is car performance. Cars are easier to handle when the tire pressure is correct. Properly maintained tires also last longer, and improve your gas mileage.

The best way to maintain your tires is to buy an inexpensive tire pressure gauge. The correct tire pressure is printed on the sidewalls -- or the outside, non-tread part -- of your tires. It's also listed in your manual, and is often listed on a sticker in the glove compartment or on the door jamb. The pressure is listed in pounds per square inch, or PSI.

Here is how to check your tire pressure:

Find an air pump at a gas station and park so that the air pump hose can reach your tire comfortably. It's best to check tires when they are cold -- that is, when you haven't been driving on them for very long.
Remove the tiny black valve cap on the valve that comes out of your tire, near the hubcap.
Press the round part of the tire gauge firmly onto the valve. Try to press it so that the hissing sound of air escaping from the tire stops while you're pressing. When it does, you'll get an accurate reading..
Read the gauge like a thermometer. The highest number you see closest to the stem of the gauge is the PSI. That number should match the recommended PSI for your tire
- If the gauge reading is higher than it should be, use your finger, or the notch on the opposite side of most tire gauges, to release a bit of air by pressing it on the pin inside the tire valve.
- If the gauge reading is lower than it should be, use the pump to add more air. On some pumps, you'll have to take the hose completely off the hose cradle to activate the pump. Press the head of the air hose firmly onto the tire just like you did with the tire gauge.
- Check your tire pressure with the gauge again, repeating your steps until you get the PSI right.
- Don't forget to replace the valve cap.

Changing a Flat Tire

Changing a flat can be a miserable experience for anyone. But if you have a jack, a lug wrench and a spare tire, you are half way there.

1) First Steps

When you're driving and feel the rumble of a flat tire, slow down, turn on your hazard lights and try to park the car on level ground as quickly as possible.
Put the automatic transmission into park and put the emergency brake on. If you have a manual transmission, leave it in first gear and pull the emergency brake.
If you have to park on even a slight incline, try to find a heavy object to wedge up against the good tires. This will help to keep the car from rolling when you have it jacked up.
Once you've parked, take out the lug wrench, jack and the spare tire from the trunk.
Make sure the spare tire has enough air in it.

2) Remove the hubcap and loosen the lug nuts

Pry off the hubcap with a screwdriver. Sometimes the lug wrench has a screw driver at the end of it. If it does, use that. Some cars don't have hubcaps at all.
Now use the lug wrench to loosen the lug nuts, which are the hexagonal bolts under the hubcap. If the lug nut has an L on it, turn clockwise. If it has an R or doesn't have anything on it, turn counterclockwise. Try to loosen the nuts an equal amount.
Very important: Don't remove the lug nuts yet. Just loosen them

3) Jack Up the Car

Put the jack on the ground near the flat tire, under the car frame. Make sure it is under something structural that can support the weight of the car.
Start pumping the jack, so that the top of it reaches the bottom of the car. When it does, keep going until the flat tire lifts off the ground. If the car seems unstable, lower the car, reposition the jack and try again.
Very important: Never get under the car when it is jacked up.

4) Change the Tire

Now that the flat tire is in the air, remove the lug nuts and place them in the upturned hub cap, or someplace easy to reach later.
With all the lug nuts removed, pull the tire off by pulling it toward you. It will be heavy, so be careful it doesn't fall on you
Put the spare tire on, positioning it so that the holes line up with the lug bolts.
Replace the lug nets and tighten them, turning the opposite way you did when you removed them
Put the spare tire on, positioning it so that the holes line up with the lug bolts.
Replace the lug nets and tighten them, turning the opposite way you did when you removed them
Then lower the jack even further and remove it.
Put the flat tire, hubcap, jack and the lug wrench back in the trunk.
Don't forget to remove the wheel blocks.
Get your original tire fixed as soon as you can. Your spare may be only good for short distances at low speeds.

Car Tire Replacement Advice

When your tires wear out, you have to decide how you?re going to replace them. Often it's not just a simple matter of buying the exact tires that came with the car -- they may have been discontinued; may cost a lot more than a comparable brand; or may not fit your driving style. Don't skimp on your tire purchase if you care about your car's ride and handling. Conversely, if you only drive sedately and your car's expensive low-profile performance tires have worn out, don't break the bank to replace them if a lesser tire will fit. Determine if you want to stay with the same kind of tire that came with the car, or upgrade to something better (and more expensive...). Price out similar tires made by a few different manufacturers so you can find the best deal.

Tire prices vary considerably. Dealerships charge the most for tires. Service stations and auto parts stores are also expensive. Tire stores are generally expensive, but can have some good deals. Department stores have good prices, especially when they have sales. Wholesale stores and shopping clubs have even better prices. Low tire prices, and a large selection, can be found through mail order suppliers -- even after shipping charges are figured into the price.

No matter where you buy tires, buy a name brand. Low quality is the reason why unknown brands remain unknown. The major brands are -- Bridgestone, Dayton, Firestone, Continental, Cooper, General, Goodyear, Kelly, B.F. Goodrich, Michelin, Uniroyal, Armstrong, Pirelli, Centennial, Dunlop, Remington, Sumitomo, Toyo and Yokohama. Sears department stores also sell major manufacturer?s tires under the Sears brand name.

Three different charges are incurred when buying new tires. The first and the most expensive is the basic cost of the tire. Then there is a fee to mount and balance your tires. (Shop around, these fees vary widely.) There is also a nominal charge for new valve stems. Many large retail stores mount and balance tires and provide lifetime rotations and road hazard insurance for one surprisingly low fee.

Any warranty is better than no warranty, but don?t make a tire purchase based on this criteria alone. A tire warranted to go 70,000 miles might be a bad choice. Its hard rubber tread won't wear out quickly, but won't provide good traction either. Also, basic tire warranties only cover defects in workmanship and materials. It is difficult to prove that your driving style and lack of maintenance weren?t to blame for early wear-out.

Modern tires are usually not defective and do not often go flat -- "road hazard" or tire insurance is not necessary unless your car is rolling on some very expensive rubber.

Tire talk: Reading Specifications

2008-01-31T08:33:00.000-08:00

Tire Specifications

When it's time to replace your tires, you have to know what brand and type you want, as well as their size. This information is printed on the sidewall. Brand name and tire name are easy enough to find sometimes they're even printed in raised white letters.

Tire size is measured in a combination of millimeters, letter codes and inches. The size of the tire pictured above is: P205/60SR15. The first letter is "P" for passenger tire. The first number is the tire?s width in millimeters -- in this case 205mm. The second number is its aspect ratio -- the ratio of sidewall height to width (also known as "profile"). In this case the sidewall height is 60 per cent of 205mm -- or 123mm. This tire is speed-rated, so the second letter is the speed rating -- in this case it?s "S" (112 mph).

Speed ratings give a general idea of a tire's overall performance characteristics -- a family sedan needs no more than an "S" rated tire, while a Ferrari will use a "Z" rated tire. Tires with high speed ratings are more expensive and shorter-lived than tires with low speed ratings. Speed ratings use the following letter codes:

Q	99 mph
S	112 mph
T	118 mph
U	124 mph
H	130 mph
V	149 mph
Z	149 mph & over

Speed rating

A letter imprinted on the tire sidewall which indicates the maximum speed that a tire is designed to withstand if it is properly inflated and not overloaded, for short periods of time. The speed rating appears in one of two forms depending on the marking system used on the tire. If it is present, the rating will appear as a letter preceding the construction type designator (as in P175/70HR13 or 225/50VR15) or it will appear following the load index (as in 195/60R14 85T).

All European tires carry a speed rating, ranging from A5 (a maximum of 15 mph for forklift tires) to Z (speeds above 149 mph).

Some U.S.-produced tires carry speed ratings, some do not because in this country the only requirement is that any new tire must be capable of 85 mph. The most common speed ratings are: S (112 mph), T (118 mph), H (130 mph), V (149 mph), W (167 mph) and Z (higher than 149 mph).

The ability to withstand higher sustained speeds is only one characteristic of speed-rated tires. Speed ratings are not so much a measure of speed as they are a measure of performance and quality. Generally, the higher a tire's speed rating, the better its resistance to head build-up. It will provide better wet and dry traction and stability and thus will have enhanced ability to corner, brake and accelerate. The next letter is "R" for radial construction -- a superior design to the bias ply tires of old. The last number designates the wheel diameter -- this tire mounts on a 15-inch wheel

Sometimes a load index and a speed rating are printed together following the size designation. This tire's size is: P205/60R15 85S. "85S" means that this tire?s load index is 1135 lbs. and it has a speed rating of "S." This means that four tires can safely carry a maximum weight of 4540 lbs. (4 tires x 1135 lbs.) at 112 mph. This is something most drivers never have to worry about, but here?s a sampling of some load ratings:

75	853 lbs.
85	1135 lbs.
88	1235 lbs.
91	1356 lbs.
93	1433 lbs.
105	2039 lbs.

Some light truck tires use a different sizing system.

This tire's size is LT 31X10.5R15. The first two letters stand for "light truck." The first number is the tire?s diameter in inches -- in this case, 31-inches. The second number is its width in inches, 10.5-inches. The "R" stands for radial. The 15 designates wheel diameter -- this tire is made to fit on a 15-inch wheel.

The very small type on the tire's sidewall contains the following information:

Uniform Tire Quality Grades are also printed on the sidewall. These grades are a result of government mandated tests that measure tread wear, traction and temperature resistance. The actual testing and grading is done by the manufacturer, so take these ratings with a grain of salt.

Tread wear measures how long the tread should last compared with a reference standard of 100. A tread wear rating of 400 means that the tread wears four times as well as the standard. This grade is only accurate for comparing tires within a certain brand.

Traction is a measurement of a tire's ability to stop in a straight line on a wet road. The highest grade is AA; A is good; B is intermediate; and C is the worst.

Temperature measures a tire's ability to withstand the heat build up caused by prolonged high speed driving, under inflation, or overloading. The highest grade is A; B is intermediate; and C is the worst.

M + S: Means the tire has the minimum required mud and snow traction.

Maximum Load: Maximum weight that the individual tire can support -- shown in pounds or kilograms.

Maximum Inflation Pressure: Shown in psi (pounds per square inch) or kPA (kilopascals). Never inflate your tires over the maximum inflation pressure.

D.O.T. Serial Number: Shows compliance with Department of Transportation regulations along with the coded name of the tire manufacturer and the place and date of manufacture. The date of manufacture is shown by the last three digits of the serial number -- Because rubber can dry out and deteriorate, tires that are extremely old can be more prone to failure than newer tires.

Tire Construction: Shows the number and type of plies (interwoven belts) which make up the tire's tread and sidewall.

Tire talk: Kinds of Tires

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No tire can handle every road condition and driving style perfectly. Positive attributes are always offset by negative factors, as the following list of tire types shows:

All-Season Tires: The Jack-of-all-trades of the tire world, and, as a result, they're the most compromised. They provide only adequate traction and handling, but they have long tread life and a smooth, quiet ride. They're also relatively affordable.

Touring All-Season Tires: These tires combine good handling with a civilized ride. Their performance oriented construction means that they?re somewhat noisier and harsher than regular all-season tires. They're also more expensive than regular all-season radials, but last just as long. Some manufacturer?s arbitrarily add "touring" to a tire?s name as a selling point.

Performance Tires: Wider tread and lower profiles combine good looks with good grip for precise, high-speed driving. Performance tires tend to have a harsh, noisy ride, relatively poor wet traction, bad snow traction, and they wear out faster than all-season radials. They?re also much more expensive. The price of ultra-high performance tires can cause your jaw to drop.

Conventional Snow Tires: Have chunky, aggressive treads that dig down to pavement covered by snow and ice. They?re noisy and handle poorly on dry roads. They're more expensive than all-season radials. They should last a long time, especially since they're only on the car for one season each year. Studded snow tires have tiny metal studs embedded in the tread for even better traction. (These days snow tire use is less common than in past decades. If you live in a place where it snows, and you drive a rear-wheel drive car, invest in a set of snow tires.)

"High-Tech" Snow Tires: Have precision engineered tread patterns and state-of-the-art multi-cell compounds which lend to good ice/snow traction and stopping ability. They can be used all year, but they?re noisy and somewhat clumsy on dry pavement. They're expensive and wear out quickly.

Light Truck Tires: Specifically designed for trucks and sport-utility vehicles, yet they are as diverse as passenger car tires. "Highway ribbed," on-road tires emphasize civilized ride and handling, while aggressive "off-road" or "mud tires" have a loud, harsh ride and sloppy handling on pavement. Light truck tires are more expensive than passenger car tires due to their larger sizes, higher load ratings and heavy-duty construction. Deep treads mean that they'll last a relatively long time.

There are a variety of specialty tires:

Rain Tires: Have a drainage channel in the tread that directs water away from the tire's surface more efficiently than conventional drainage grooves.

High Flotation Tires: Big, wide tires that people put on 4x4 trucks and sport-utilities so they can drive on the sand without sinking. These tires have poor traction in the ice and snow, so put those skinny, un-cool tires back on the truck for the winter.

Directional Tires: Have a "one-way" tread pattern optimized for the direction the tires rotate on the car.

Asymmetrical Tires: Combine multiple tread patterns in order to make a more well-rounded performance tire.

Self-Sealing Tires: Have a flexible inner-lining that seals around an object if punctured, stopping air loss.

"Twin" Tires: This setup employs two thin, "half-width" tires which are mounted on a special wheel. If one tire goes flat, the other "half" can still support the car.

"Run-flat" Tires: Use special rubber compounds and reinforced sidewalls that can support the car even when deflated -- allowing limited travel.

"Lifetime" Tires: Last for many years, as the name suggests. These tires wear out very slowly while delivering adequate traction.

Repair Guide: Power-Assisted Brakes

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A power-assist brake system is used on most cars to reduce the braking effort required by the driver. There are two general types of power-assist brakes. The most common type uses an intake manifold vacuum acting on a diaphragm to provide the power assist. The other type uses hydraulic power developed by a pump to provide the assist. The vacuum power-assist brake uses a large diaphragm in a canister behind the master cylinder. The canister is connected by a hose to the engine intake manifold. The push rod connected from the brake pedal goes through the power-assist unit on its way to the master cylinder. Inside the canister is a large diaphragm. This diaphragm is connected to the push rod. Engine intake manifold vacuum is applied to both sides of the diaphragm. When the brakes are applied, valving inside the canister is operated by the push rod. Atmospheric pressure is admitted to one side of the diaphragm. With vacuum on one side and atmospheric pressure on the other, the diaphragm moves toward the master cylinder. Because the push rod is connected to the diaphragm, it also moves. The large diaphragm has enough force to take much of the effort of applying the brakes away from the driver.

Hydraulic boosters require a hydraulic pump to provide the power assist. In many systems, the power steering pump is used to provide power for both the power steering and power brakes. As shown below, fluid under pressure goes from the power steering pump to a hydraulic boost unit behind the master cylinder. This unit contains a power piston and valving. When the brakes are applied, hydraulic pressure pushes on the boost piston, which in turn pushes on the brake push rod. The hydraulic power takes much of the effort out of brake application.

The hydraulic booster normally has an accumulator, which is a device that is spring loaded or charged with pressurized gas. This device provides emergency pressure to apply the brakes should the power steering flow be interrupted for any reason. The system is good for one to three stops, depending on the type of accumulator. Dash warning lights indicate when the system has failed.

CAUTION: Accumulators are under very high pressure. Never disassemble an accumulator without specific instructions to do so in a shop service manual. Incorrect disassembly procedures could cause the accumulator to fly apart and injure you.

Repair Guide: Parking Brakes

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The parking brake assembly is designed to apply the brakes mechanically to prevent the car from rolling when parked, or to stop the car in the event of a complete hydraulic failure. Most parking brakes operate on the two rear brakes. Some vehicles with front wheel drive have front wheel parking brakes. In these cases, in an emergency stop, most of the stopping power would be required on the front of the car.

The parking brake may be activated by a hand lever or a foot pedal. In either style, pushing the pedal or pulling the lever causes a cable connected to the rear brakes to be pulled. The cable has an equalizer so that the cable pulls the same amount on both left and right rear brakes.

The parking brake lever is connected to the secondary brake shoe. The lever is mounted on the back of the shoe and is connected to it by a pivot pin located in the upper end of the lever. The pivot pin is retained in the shoe by a washer and clip. The parking brake cable is attached to the lower end of the lever. A strut, located below the lever pivot pin, connects the lever to the primary brake shoe. The strut is notched at each end and is fitted into accommodating notches in the lever and primary brake shoe. An oval-shaped spring, installed on the primary shoe end of the strut, is used to position the strut.

When the parking brake is applied, the cable pulls the lower end of the parking brake lever forward, causing the connecting strut to push the primary brake shoe forward. At the same time, the upper end of the lever pushes the secondary brake shoe rearward. The combined action of the lever and strut expands the brake shoes, forcing them against the drum to develop brake action.

Repair Guide: Master Cylinder, Brake fluid, Bleeding

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The master cylinder is a type of hydraulic pump operated by the driver through the pedal and push rod. The master cylinder push rod is connected to a piston inside the cylinder. There is hydraulic fluid in front of the piston.

When the pedal is depressed, the master cylinder piston is pushed forward. The fluid in the master cylinder and the entire system, being incompressible, transmits the force exerted by the master cylinder piston to all the inner surfaces of the system. At this point, only the pistons in the wheel cylinders or caliper are free to move, and because the hydraulic fluid is not compressible, the pistons move outward to force the brake shoes against the brake drums or rotors.

There are two basic advantages of using a hydraulic system to operate the brakes. First, fluid lines are easy to route from the master cylinder to each of the wheel brake units. Second, hydraulics allow us to multiply the force used to apply the brake shoes. When you use a hydraulic jack to lift a car, you are multiplying your effort using the principles of hydraulics. This multiplying effect is done using the principles of pressure and force.

Pressure can be defined as the amount of force applied to a specific area. Suppose a hydraulic pressure of 10 psi (pounds per square inch) were applied to an object with a surface area of 16 square inches. The total applied force would equal 160 pounds (10 psi pressure times an area of 16 square inches). If the same 10 PSI were applied to an object with a surface area of 2 square inches, a force of 20 pounds would be applied. The relative size of the master cylinder piston and the pistons used at the wheel brake units allow the driver's brake pedal effort to be multiplied hydraulically.

Master Cylinder Construction and Operation

The master cylinder is constructed of two main parts: a reservoir and a master cylinder body. The reservoir provides a supply of brake fluid for cylinder operation. All current reservoirs are split designs. This means they provide two separate storage areas for two separate piston assemblies. The split design allows for separating the front and rear, or one front and one rear system, from each other in case of hydraulic failure.

The reservoir may be cast as one piece with the cylinder body or it may be a separate plastic container. All reservoirs have a removable cover or caps so that brake fluid can be added to the system. A flexible rubber diaphragm at the top of the master cylinder reservoir seals the hydraulic system from possible entrance of contamination while permitting expansion or contraction of the fluid within the reservoirs without direct venting. There are two holes, or ports, at the bottom of each reservoir section. One is called the replenishing port, the other a vent port. These ports permit passage of fluid between each pressure chamber and its fluid reservoir during certain operating conditions.

The body is a long aluminum or cast iron cylinder positioned under the reservoir. Inside the cylinder are two spool-shaped pistons. The pistons are fitted with rubber seals used to prevent fluid from leaking around the pistons. One piston is called the primary, the other the secondary. Each piston provides a separate hydraulic system for the front and rear brakes or on the diagonal system between one set of front and rear brakes. Springs in the cylinder return the pistons into position after braking. Two outlet holes provide the connection for the hydraulic lines. A snap ring holds the components inside the cylinder and a boot fits around the rear of the cylinder and push rod to prevent dirt from entering the cylinder.

The operation of the primary and secondary piston is the same. We examine how one piston works when the brakes are applied. When the brake pedal is depressed, force is transferred through the push rod to the master cylinder piston, which moves forward. After the primary seal covers the replenishing port, the master cylinder chamber is closed to the reservoir so that further piston travel builds up pressure. Fluid is then forced through the outlet into the lines leading to the wheel cylinders. When the brakes are released, return springs in the drum brake mechanisms pull the shoes away from the drums. This movement pushes the wheel cylinder pistons inward, forcing fluid back through the lines to the master cylinder. However, the master cylinder piston returns to the released position faster than fluid can fill the chamber, thus creating a momentary vacuum. To compensate for the vacuum, fluid flows from the reservoir, through the vent port, through the vent holes in the piston, and around the primary seal.

The dual master cylinder operates in the same manner as the single unit just described, except that it provides two independent systems, one for the front brakes and one for the rear, or one for each diagonal set of front and rear brakes. Under normal conditions, when the brakes are applied, the primary piston moves forward. At the same time, a combination of hydraulic pressure and the force of the primary piston spring moves the secondary piston forward. When the pistons have moved forward so that their primary seals cover the replenishing ports, hydraulic pressure is built up and transmitted to the front and the rear wheels.

In case of a hydraulic failure in the rear brake system, the primary piston will move forward when the brakes are applied, but will not build up hydraulic pressure. Only a small force is transferred to the secondary piston through the primary piston spring until the piston extension screw comes in contact with the secondary piston. Then, push rod force is transmitted directly to the secondary piston and enough pressure is built up to operate the front brakes.

If there is a hydraulic failure in the front brake system, both pistons will move forward when the brakes are applied, just like normal. Due to the front system failure, however, there is nothing to resist secondary piston travel except the secondary piston spring. This permits the primary piston to build up only negligible pressure until the secondary piston bottoms in the cylinder bore. Then, enough hydraulic pressure will be built up to operate the rear brakes.

Brake Master Cylinder Fluids

The brake system uses hydraulic power generated by a master cylinder to activate the four wheel brake assemblies. A fluid reservoir is located on top of the master cylinder. The fluid level in the brake master cylinder must be checked regularly at intervals specified by the manufacturer.

Brake fluid is a specially formulated liquid that must meet Society of Automotive Engineers and federal standards. These specifications list the necessary qualities of a brake fluid. The following are the most important:

Must flow freely at low and high temperatures.
Must have a high boiling point (over 400F).
Must not deteriorate metal or rubber brake parts.
Must lubricate metal and rubber parts.
Must be able to absorb moisture that enters the hydraulic system.

Brake fluid is rated by the Department of Transportation (DOT). The brake fluid is then assigned a number. The common ratings are DOT 3, DOT 4, and DOT 5. The higher the number, the higher the fluid's boiling point. The DOT rating is found on the can of brake fluid. The shop and owner's manual specify what rating is correct for the car. Do not use a brake with a lower DOT rating than specified by the manufacturer. The lower rated fluid could boil and cause a loss of brake effectiveness.

Most brake fluid is glycol based. The word 'glycol' is usually not shown on the front of the container. The word 'silicone' is shown next to the name of the brake fluid if it has a silicone base. Always use the correct type of fluid specified in the shop or owner's manual. Do not mix the types of fluids. If you use the incorrect type of fluid you might cause a loss of brake efficiency.

WARNING: Brake fluid must always be stored in clean, dry containers. Brake fluid is hygroscopic; that is, it will attract moisture and must be kept away from dampness in a tightly sealed container. When water enters brake fluid, it causes its boiling point to lower. Fluid should be protected from contamination, especially oil, grease, or other petroleum products. Never reuse brake fluid.

CAUTION: Never use gasoline, kerosene, motor oil, transmission fluid, or any fluid containing mineral oil to clean brake system components. These fluids will cause the rubber cups and seals in the master or caliper units to soften, swell, and distort, resulting in brake system failure.

Repair Guide: Hydraulics

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Hydraulic lines made of tubes and hoses are used to transmit fluid under pressure between the master cylinder and each of the wheel brake units. Several valves may be used in the system. A warning light pressure switch is used on all brake systems. A combination valve is used on some front disc brake-equipped cars to improve brake balance between the front disc brakes and rear drum brakes. A stop light switch is used to signal other drivers during a stop.

Hydraulic tubes are used to direct fluid between stationary brake parts. Most hydraulic tubes used in the brake system are double wall, welded steel tubes, coated to resist rust. The tube ends are double flared or have a chamber-type flare to guard against leakage. Threaded fittings are used to connect the tubes to brake parts.

The wheel brake units move up and down with the suspension. The master cylinder and steel brake tubes are mounted to the stationary body and frame. Flexible hoses are used to connect stationary brake components with moving components. Hoses must be able to withstand high fluid pressures without expansion and must be free to flex during spring deflection and wheel turns without damaging the hose. Hoses come in different sizes and lengths, with a variety of end fittings to accommodate different vehicle requirements.

The stop light switch is a spring-loaded electrical switch installed in the vehicle's stop light circuit. In some installations, the switch is operated by hydraulic pressure. In others, the switch is mechanically operated through contact with the brake pedal. With the brakes released, the circuit through the switch is open. When brakes are applied, the switch closes to complete the circuit to the stop lights.

Most late-model cars use a combination switch that contains a warning light switch, a metering valve, and a proportioning valve. The warning light switch is designed to light a brake warning lamp on the instrument panel if there is a hydraulic failure in either side of the split system. The switch works by sensing a pressure difference between two hydraulic circuits.

The switch body has connections for the hydraulic lines from the master cylinder. Outlet connections go to the two separate systems. This can be the front and rear wheels. On the diagonal style, a left front and right rear is paired together. The right front and left rear are separate systems.

A small switch piston is positioned between the two hydraulic systems. A spring positions the switch piston in the center of the switch. When the pressure is equal in both the front and rear hydraulic systems, the switch piston remains centered and does not contact the switch terminal in the bore of the switch.

If pressure fails in one of the hydraulic systems, hydraulic pressure moves the piston toward the inoperative side. The piston moves off-center to push up a switch pin. The switch pin activates the contacts inside the electrical terminal. This provides a ground for the warning lamp circuit and lights the warning lamp.

Most cars that use front disc brakes and rear drum brakes use a metering and proportioning valve in the system to achieve balanced braking between the front and rear wheels. The purpose of the metering valve is to improve braking balance, particularly during light brake application.

The metering valve keeps the front discs from operating until the rear drums have started to work. The valve is needed because disc brakes are fast acting; drum brakes have spring tensions and play in linkages to overcome first. The valve is located in the line to the front brakes. It works on fluid pressure and is normally closed. When the brake pedal is depressed, the fluid flows first to the rear brakes. As they begin to take hold, the system pressure builds up enough to open the metering valve, admitting pressure to the front brakes. Once open, the valve has no effect. The effect of the metering valve is felt during the beginning stages of all brake applications and throughout the duration of light brake applications. The proportioning valve is installed in the hydraulic circuit going to the rear drum brakes. Its function is to maintain the correct proportion between line pressures to the front and rear brakes and, therefore, provide a balanced vehicle braking system.

The proportioning valve reduces the hydraulic pressure at the rear drum brakes when high pressure is required at the front disc brakes. The valve helps to prevent premature rear wheel lock-up and skidding during heavy brake applications and provides better braking balance.

The Modern Hydraulic System

When you think about it, it's pretty hard to believe that a teeny tiny column of fluid can transmit enough force to stop a ton or two of hurtling automobile, but that's the magic of hydraulics. Early cars used mechanical apply set-ups -- cams, cables, and levers. No matter how clever the design, however, they were almost impossible to equalize perfectly, and required constant adjustment, so the idea of using hydraulics to do the job intrigued engineers from about 1897 onward. But it took many years to develop reasonably dependable systems, so the first domestic car with fluid pressure-actuated brakes was the '21 Dusenberg, and Chrysler followed in '24.

With refinements, hydraulic systems essentially the same as those originals got us through four decades. But in the mid-60's the changes and complications started. First there were discs and dual circuits with metering, proportioning, and a warning light, then came combo valves, diagonally-split systems, low-drag calipers, Quick Take-Up/step-bore masters, load-sensitive proportioning, etc. (ABS is another whole subject I won't tackle here except for maintenance).

A firm grasp of the modern hydraulic system and the service procedures it requires is about as important to anybody doing brake work as remembering to breathe. Unfortunately, I've found that lots of you out there still have some fuzzy areas in that essential understanding and also harbor a few misconceptions and prejudices.

Fail safe

A case in point is the dual, split, or tandem master cylinder, which has been used on every car sold in this country since 1967 (although Cadillac had it as far back as '62). Plenty of people still aren't comfortably familiar with its construction and operation.

A typical modern specimen will be of the composite variety (in other words, aluminum with a plastic reservoir), but iron one-piece units are still around in abundance. Two pistons ride in the bore, the rear piston being the primary, and the front the secondary.

Each piston has a primary cup at its front and a secondary at its rear, so you'll be hearing such combinations as primary piston secondary seal, secondary piston secondary seal, etc. The primary seals are the most important because they trap the fluid that's about to be squeezed into the lines. The primary piston's secondary seal keeps fluid from escaping out of the back of the cylinder, and the secondary piston's secondary seal acts as a barrier to make two essentially separate cylinders out of one. In normal braking, the pushrod from the pedal or booster forces the primary piston forward. No pressure is created until the primary seal covers the compensating or vent port from the reservoir, but once it does fluid is trapped in the chamber between the pistons and becomes, for all intents and purposes, a solid column. Pressure is routed from this chamber to two wheels. A combination of the trapped fluid and the primary piston coil spring bears on the secondary piston, moving it forward also and creating pressure in the chamber ahead of the secondary piston's primary seal, to which the line to the other two wheels is attached.

When the pedal is released, a partial vacuum occurs in both pressure chambers because the fluid is too lazy to return from the lines fast enough. So, in order to re-arm the brakes instantaneously, the primary seals are designed to allow fluid to flow one way (forward) from behind each seal into the pressure chambers.

The replenishing ports allow fluid to move freely between the chambers behind both pistons' primary cups and the reservoir according to demand and expansion and contraction from temperature changes.

Blow out

If a hose lets go or a saboteur has sawed through one of the brake lines so there's a catastrophic loss of fluid in half the system, the other half will still provide a means of decelerating the vehicle, albeit with a lower pedal and reduced stopping power. Both pistons have extensions which project out in front of their primary seals. A failure in the circuit that's connected to the primary piston's pressure chamber will allow the piston to move forward enough so the extension will bear on the secondary piston, push it ahead, and generate pressure in the other circuit. If, on the other hand, the circuit that gets its juice from the secondary chamber blows, the extension on the secondary piston will bottom out on the front of the cylinder and the fluid trapped between the pistons will operate the alternate set of brakes.

The residual pressure valve was once common in outlet ports that go to drum brakes. It maintained 5-20 psi in the lines to keep the wheel cylinder cups in constant contact with their bores. Most cylinders today have those little metal expanders behind the seals that make this unnecessary. If somebody were to install a check valve in a disc brake circuit, he'd create a constant dragging condition because discs are designed to work with very little clearance.

Initial burst

Since the GM X-Car appeared in 1980, there's been another complication: the Quick Take-Up/step-bore master cylinder. The engineers were trying everything possible to get the last tenth of an mpg, so the rolling resistance that zero-clearance discs caused was quite enough to warrant the adoption of low-drag calipers. Piston seal grooves were machined at an angle so the seals retracted the pads a sufficient distance to eliminate this parasitic loss, but that meant a master that displaced a large volume of fluid quickly was required.

The design arrived at uses a stepped bore and a primary piston with a small front and a larger rear diameter. During the first part of the stroke, the large part of the piston naturally displaces more fluid than the small part, and this extra volume goes around the lip of the small seal into the chamber between the primary and secondary pistons, moving the secondary ahead more than the distance the pushrod has traveled. That way, extra fluid is displaced into both circuits. A logically-named Quick Take-Up valve, which is connected to the rear high-volume chamber, vents excess fluid up into the reservoir once a certain psi is achieved, and also acts as the refill passage for the large chamber.

Other manufacturers have followed suit, as with the Tokico master you'll find on some FWD Fords, which features what's called a "Fluid Control Valve" to give essentially the same action as the GM unit.

Balancing act

But a master cylinder alone does not an integrated brake system make. Means of fine-tuning the pressure for the situation and warning the driver of a partial failure are equally important. All kinds of individual and combination valves are used to perform the metering, proportioning, and warning light activation functions, and I'll consider these jobs one at a time.

Disc brakes operate with very little clearance between the pads and the rotor, so the instant the caliper receives pressure, the drag on the wheel begins. But drums are different. There's considerable space to be taken up before the shoes go to work. If a disc/drum combination were connected directly to the same master, the discs would end up doing far more than their share. The metering or hold-off valve is what divides the load fairly. It stops the flow of fluid to the calipers until pressure reaches 75-125 psi or so, then it opens. This gives the drums a chance to catch up, so both types of brakes start applying at the same time. If you use a pressure bleeder during service, the metering valve will have to be deactivated, which is usually done by pulling on or depressing a pin.

Since drum brakes are self-energizing and commonly duo-servo whereas discs work entirely by means of hydraulic force, drums tend to lock up in hard stops. Weight transfer adds to the problem of rear over-braking, so even vehicles with discs all around need some means of keeping the posterior decelerators within bounds, and the proportioning valve was invented to do the job.

This device limits the flow to the rear brakes after a certain pressure has been reached, and this "split point" can be anywhere from 200 to 500 psi. Above that, force in the rear lines is allowed to rise at only a portion of the maximum available. The valve does absolutely nothing in normal, low-pressure stops. On front/rear split systems, if the front circuit fails, the valve is bypassed to allow full hydraulic power to reach the rears.

A further refinement is the load-sensing proportioning valve, which you'll find on various pickups, vans, utility vehicles, and even some cars (the first one I ever saw was on a '71 Fiat). The idea here is to use the distance between the body and the axle to adjust rear stopping power to match the weight on the posterior wheels and prevent lockup. Linkage connected to a lever on the proportioning valve varies the pressure available. You'll have to bleed this set-up with the vehicle's weight on its wheels because the valve will shut off the flow if the axle is hanging. Typically, these valves have adjustable linkage, but be certain to follow the specific service recommendations before fooling with them. One mm of adjustment can change pressure by 60 psi.

Mayday!

The extra safety the dual brake system provides carries a subtle danger with it: If one half springs a leak and the driver isn't sensitive enough to notice that he's pushing the pedal harder and farther than normal, he might ride around indefinitely with severely inadequate brakes. So, a dash light is provided that winks on when one circuit is in trouble, and it's activated by the pressure differential switch. Basically, this is a piston that remains centered in its cylinder as long as there's equal psi in both circuits. If one side blows, the pressure of the other pushes the piston toward the open side, and this movement closes the switch to the warning light.

Separation

What's the best way to divide a dual system? Well, the original domestic approach was to put both fronts on one circuit and both rears on the other. That works fairly well should the posterior brakes blow. But if the fronts go out, you've got vastly reduced stopping power and the tendency to skid if you lock the wheels. With FWD the situation became untenable because the rear wheels are so lightly loaded.

Enter dual-diagonal wherein one front and one rear on opposite sides share a circuit. This added the need for some additional plumbing (two proportioning valves, for instance), but gave more reasonable emergency deceleration ability in return. Bleeding sequence changed from the traditional RR, LR, RF, LF to RR, LF, LR, RF.

The ultimate system for safety is what you'll find on non-ABS Volvos: Both fronts and one rear will operate even if one circuit fails. This is accomplished by using two- or four-piston calipers with one side of each plus one rear brake connected to half the system. One pad of each disc brake will always be operational.

Tube types

The metal brake lines that route pressure to the wheels haven't escaped change. They're still made of double-wall steel, but a different type of fitting is taking over. Called the ISO (International Standards Organization) flare, it's not compatible with traditional double-flare/tube seat connections. Because the shoulder of the nut bottoms in the fitting, sealing pressure is uniform and over-tightening ceases to be a problem. Also, only one simple die is required to form the flare.

Brake Fluid

Then there's brake fluid, the stuff that makes everything happen. Modern DOT 3 and 4 glycol are both pretty good because they have high boiling points and the ability to hold lots of moisture. But that affinity for water made another type seem attractive: silicone, rated DOT 5 and color-coded purple. It doesn't absorb H2O, so was expected to practically eliminate corrosion, has a 500 degree F. boiling point, and won't dissolve paint the way ordinary glycol does.

Why hasn't everybody gone to silicone? Because there are drawbacks and unanswered questions. First, it's way more expensive than DOT 3 or 4, but a few dollars wouldn't really make much difference in the average price of a car today. It's the unresolved performance characteristics that have kept the carmakers from filling hydraulic systems with DOT 5 at the factory. Seal life is one problem. An aftermarket brake engineer I know told us he has trouble getting cylinder cups to make it through the SAE longevity test with silicone -- they get hard and wear out, he says. And, if any moisture should find its way into the system, it tends to collect in slugs. When elevated temperatures are encountered, especially at high altitudes, these can turn to bubbles resulting in a loss of stopping power.

The auto makers just don't consider silicone's potential advantages worth the risk. After all, a typical brand-name super heavy duty DOT 3 has a dry boiling point of 485 deg. F., which is only 15 deg. less than silicone (wet, this falls to 310 deg., but there's no excuse for running around with watered-down fluid, as I'll explain).

Proceed

Now for some service tips that'll help you avoid problems. The first thing I'd like to mention is that you should always open the bleeder before bottoming out those caliper pistons. Otherwise, you'll back flush nasty sediment up into the works. This is bad enough with a regular master, but with all the tiny passages in an ABS it can cause big trouble. Just do it.

Then there's flushing and refilling the system with fresh fluid. In the past, some brake experts said it wasn't worth the effort because you can't get all the old stuff out unless you disassemble the calipers and cylinders. True, you won't be able to eliminate every drop of the contaminated liquid, but you can get most of it, and that will effectively reduce the amount of moisture in the circuits.

This has always been important for corrosion prevention, but now the high operating temperatures encountered with semi-mets and FWD make maintaining a high boiling point critical to safety even for the average motorist. Besides water, there's sediment, which is a combination of rust and the ashy residue of burned glycol. Expensive and intricate ABS hardware is further justification for this maintenance. Many of these systems are vented to the atmosphere, and there's also contamination from under-hood vapors in some layouts. Fluid changes are cheap insurance against big-bucks repairs.

Depending on the authority, recommended intervals range from one to three years.

New pipes?

Whenever you've got a car up in the air, take a careful look at the metal lines and rubber hoses. In my own shop, I see total circuit failures due to corroded lines or blown hoses frequently enough to be very conscientious about this. If a line runs up over the chassis so that it's hard to see, use a mirror and your sense of touch.

Replace lines if the rust has reached the scaly stage. When installing replacements, follow the original routing as closely as possible. I often hear of fade or low pedal problems because one of these lines has been mounted too close to an exhaust pipe, or has a hump or loop in it that traps air.

Those flexible hoses are so well made they often survive for the life of the car, but why push your luck? I almost took an icy dip in Lake Michigan when one blew on my pre-dual master '66 Ford, so I consider their replacement valuable insurance. You could use some carmakers' service literature to support the idea of new hoses as regular maintenance -- the Ford Fiesta manual, for example, says hoses should be retired after 36K miles. A related item is the high pressure ABS hose between the pump and the accumulator, which some car makers want you to replace at 60,000 miles.

Bubble trouble

Air expulsion definitely deserves some space because there's more to it than just observing the proper sequence. Bench bleeding master cylinders, for instance. Neglecting this is the number-one reason for spongy pedal complaints, and some re-manufacturers include fittings, tubes, and instructions in the box in hopes of reducing the number of unnecessary returns.

You can do this job by just holding your fingers over the outlet tubes to keep air from being drawn in on the return stroke, but that's pretty messy, so I'll give you the procedure using tubes. Clamp one of the master's mounting ears in a vice so the unit is as level as possible. Position the tube tips well below the level of fluid in the reservoir, then use a rod or drift to stroke the piston SLOWLY. Especially on Quick Take-Ups and their equivalents, wait at least 15 seconds between strokes to allow the low pressure chamber to release all its bubbles and fill completely. Keep stroking until there's no more evidence of air at the tube tips and ports.

Should you get a car with a replacement cylinder that some other service personage didn't bench bleed, you might be able to do it with the master in place providing you can jack the rear of the vehicle high enough to get the cylinder level. Surge bleeding -- you know, where you pound the pedal violently a bunch of times to get the bubbles mixed up with the fluid, then crack the line -- is frowned upon by experts who don't think aeration is ever a good idea.

By the way, one major brake outfit (EIS) has done us a favor by providing aftermarket step-bore master cylinders with a bleeder that facilitates getting out all that trapped air. Located in the low-pressure side of the cylinder below the Quick Take-Up valve, it gives those bubbles a convenient exit path. This little feature can reduce bench bleeding time to maybe three minutes, and practically eliminates low-pedal comebacks.

When it comes to the bleeders at the wheels, I know most of you just open them and let the fluid squirt. But besides making slippery puddles on the floor, it can shoot farther than you might expect, perhaps ruining the paint on a nearby car. I use a transparent tube and bottle set-up that hangs by a magnet because it's neat and it lets me see what I'm getting out. Also, it eliminates the need for a helper if I'm not using a pressure bleeder.

Then there are the bleeder screws themselves. You haven't worked on cars very long if you haven't encountered a frozen one that breaks off before opening. My rather drastic and primitive method of clamping Vise-Grips to the screw and shaking it while I heat the cylinder or caliper around the port with a propane torch often works, but there's a better answer. Whenever you get a vehicle in that hasn't yet developed the problem, unscrew the bleeders and coat their threads with just a touch of anti-seize. Ditto when you replace a caliper or cylinder. If you get that conveyance back later for brake work, you'll be glad you took the time.

Caliper Care

In an ideal world, every caliper would be overhauled during a reline to insure against piston seizure and seal failure. And that's what most authorities recommend. But when was the last time you encountered a leaky caliper? They last and last in most cases. So, if you're under time or cost pressure, you could just push those pistons back (bleeder open, of course). One caveat: If you feel any roughness or binding as you force a piston home, you'd better get inside.

What about wheel cylinders? The frequency of leaks here is so high most of the good techs overhaul or replace them in every case.

Repair Guide: Disc/Drum Brakes

2008-01-31T07:55:00.000-08:00

Disc brakes are used on the front wheels of most cars and on all four wheels on many cars. A disc rotor is attached to the wheel hub and rotates with the tire and wheel. When the driver applies the brakes, hydraulic pressure from the master cylinder is used to push friction linings against the rotor to stop it.
The rotor is usually made of cast iron. The hub may be manufactured as one piece with the rotor or in two parts. The rotor has a machined braking surface on each face. A splash shield, mounted to the steering knuckle, protects the rotor from road splash.

A rotor may be solid or ventilated. Operation of the master cylinder if there is a rear system failure. Ventilated designs have cooling fins cast between the braking surfaces. This construction considerably increases the cooling area of the rotor casting. Also, when the wheel is in motion, the rotation of these fan-type fins in the rotor provides increased air circulation and more efficient cooling of the brake. Disc brakes do not fade even after rapid, hard brake applications because of the rapid cooling of the rotor.

The hydraulic and friction components are housed in a caliper assembly. The caliper assembly straddles the outside diameter of the hub and rotor assembly. When the brakes are applied, the pressure of the pistons is exerted through the shoes in a 'clamping' action on the rotor. Because equal opposed hydraulic pressures are applied to both faces of the rotor throughout application, no distortion of the rotor occurs, regardless of the severity or duration of application. There are many variations of caliper designs, but they can all be grouped into two main categories: moving and stationary caliper. The caliper is fixed in one position on the stationary design. In the moving design, the caliper moves in relation to the rotor.

Most late-model cars use the moving caliper design. This design uses a single hydraulic piston and a caliper that can float or slide during application. Floating designs 'float' or move on pins or bolts. In sliding designs, the caliper slides sideways on machined surfaces. Both designs work in basically the same way.

The single-piston caliper assembly is constructed from a single casting that contains one large piston bore in the inboard section of the casting. Inboard refers to the side of the casting nearest the center line of the car when the caliper is mounted. A fluid inlet hole and bleeder valve hole are machined into the inboard section of the caliper and connect directly to the piston bore.

The caliper cylinder bore contains a piston and seal. The seal has a rectangular cross section. It is located in a groove that is machined in the cylinder bore. The seal fits around the outside diameter of the piston and provides a hydraulic seal between the piston and the cylinder wall. The rectangular seal provides automatic adjustment of clearance between the rotor and shoe and linings following each application. When the brakes are applied, the caliper seal is deflected by the hydraulic pressure and its inside diameter rides with the piston within the limits of its retention in the cylinder groove. When hydraulic pressure is released, the seal relaxes and returns to its original rectangular shape, retracting the piston into the cylinder enough to provide proper running clearance. As brake linings wear, piston travel tends to exceed the limit of deflection of the seal; the piston therefore slides in the seal to the precise extent necessary to compensate for lining wear.

The top of the piston bore is machined to accept a sealing dust boot. The piston in many calipers is steel, precision ground, and nickel chrome plated, giving it a very hard and durable surface. Some manufacturers are using a plastic piston. This is much lighter than steel and provides for a much lighter brake system. The plastic piston insulates well and prevents heat from transferring to the brake fluid. Each caliper contains two shoe and lining assemblies. They are constructed of a stamped metal shoe with the lining riveted or bonded to the shoe and are mounted in the caliper on either side of the rotor. One shoe and lining assembly is called the inboard lining because it fits nearest to the center line of the car. The other is called the outboard shoe and lining assembly.

The caliper is free to float on its two mounting pins or bolts. Typical mounting pins are shown in the exploded view of the floating caliper. Teflon sleeves in the caliper allow it to move easily on the pins. During application of the brakes, the fluid pressure behind the piston increases. Pressure is exerted equally against the bottom of the piston and the bottom of the cylinder bore. The pressure applied to the piston is transmitted to the inboard shoe and lining, forcing the lining against the inboard rotor surface. The pressure applied to the bottom of the cylinder bore forces the caliper to move on the mounting bolts toward the inboard side, or toward the car. Since the caliper is one piece, this movement causes the outboard section of the caliper to apply pressure against the back of the outboard shoe and lining assembly, forcing the lining against the outboard rotor surface. As the line pressure builds up, the shoe and lining assemblies are pressed against the rotor surfaces with increased force, bringing the car to a stop.

The application and release of the brake pressure actually causes a very slight movement of the piston and caliper. Upon release of the braking effort, the piston and caliper merely relax into a released position. In the released position, the shoes do not retract very far from the rotor surfaces.

As the brake lining wears, the piston moves out of the caliper bore and the caliper repositions itself on the mounting bolts an equal distance toward the car. This way, the caliper assembly maintains the inboard and outboard shoe and lining in the same relationship with the rotor surface throughout the full length of the lining.

Sliding calipers are made to slide back and forth on the steering knuckle support to which it is mounted. There is a V shaped surface, sometimes called a rail, on the caliper that matches a similar surface on the steering knuckle support. These two mating surfaces allow the caliper to slide in and out. The internal components of the caliper are the same as those previously described.

The stationary or fixed caliper has a hydraulic piston on each side of the rotor. Larger calipers may have two pistons on each side of the rotor. The inboard and outboard brake shoes are pushed against the rotor by their own pistons. The caliper is anchored solidly and does not move. The seals around the pistons work just like those already described. The main disadvantage of the stationary caliper is that it has more hydraulic components. This means they are more expensive and have more parts to wear out.

Question:

My brakes are squealing. Does that mean I need a brake job?
Answer:

Not necessarily. A certain amount of brake noise is considered "normal" these days because of the harder semi-metallic brake pads that are used in most front-wheel drive cars and minivans. This type of noise does not affect braking performance and does not indicate a brake problem. However, if the noise is objectionable, there are ways to eliminate it.
Brake squeal is caused by vibration between the brake pads, rotors and calipers. Pad noise can be lessened or eliminated by installing "noise suppression shims" (thin self-adhesive strips) on the backs of the pads, or applying "noise suppression compound" on the backs of the pads to dampen vibrations. Additional steps that can be taken to eliminate noise are to resurface the rotors and replace the pads.

Some brands of semi-metallic pads are inherently noisier than others because of the ingredients used in the manufacture of the friction material. Strange as it may sound (pardon the pun), cheaper pads are sometimes quieter than premium quality or original equipment pads. That's because the cheaper pads contain softer materials that do not wear as well. For that reason, they are not recommended. Premium quality pads should cause no noise problems when installed properly and will give you better brake performance and longer life.

Conditions that can contribute to a disc brake noise problem include glazed or worn rotors, too rough a finish on resurfaced rotors, loose brake pads, missing pad insulators, shims, springs or anti rattle clips, rusty or corroded caliper mounts, worn caliper mounts, and loose caliper mounting hardware. Drum noise may be due to loose or broken parts inside the drum.

Most experts recommend new caliper and drum hardware when the brakes are relined, a thorough inspection of the calipers and rotors for any wear or other conditions that might have an adverse affect on noise or brake performance, and resurfacing the rotors (and drums) if the surfaces are not smooth, flat and parallel.

If you hear metallic scraping noises, on the other hand, it usually means your brake linings are worn out and need to be replaced -- especially if your brake pedal feels low or if you've noticed any change in the way your vehicle brakes (it pulls to one side when braking, it requires more pedal effort, etc.).

Some brake pads have built-in "wear sensors" that produce a scraping or squealing noise when the pads become worn. In any event, noisy brakes should always be inspected to determine whether or not there's a problem. And don't delay! If the pads have worn down to the point where metal-to-metal contact is occurring, your vehicle may not be able to stop safely, and you may score the rotors or drums to the point where they have to be replaced.

Question:

How can I tell if a rotor or drum really needs to be replaced?
Answer:

A rotor must be replaced if it is at or below the minimum thickness specification or discard thickness stamped on the rotor (this same information can also be found in brake service manuals). Replacement is also necessary if a rotor cannot be resurfaced without exceeding the minimum thickness specification or the discard thickness specification. Replacement is also required if the rotor is cracked or damaged. Replacement may be recommended if a rotor has hard spots, is warped, or has been previously resurfaced for a warped condition.
A drum must be replaced if it is at or beyond the maximum inside diameter specification or discard diameter stamped on the drum. Replacement is also necessary if a drum cannot be resurfaced without exceeding the maximum diameter specification or discard diameter specification. Replacement is also required if a drum is cracked, damaged, bell mouthed or too far out of round for resurfacing.

Question:

Is it always necessary to resurface the rotors and drums when the brakes are relined or to rebuild or replace the disc brake calipers and drum brake wheel cylinders?
Answer:

No. The rule here is resurface when necessary, don't resurface when it isn't necessary. If the rotors and drums are in relatively good condition (smooth and flat with no deep scoring, cracks, distortion or other damage), they do not have to be resurfaced. Resurfacing unnecessarily reduces the thickness of these parts, which in turn shortens their remaining service life.
According to the uniform inspection guidelines developed by the Motorist Assurance Program (MAP), "friction material replacement alone does not warrant rotor reconditioning." Whether or not the rotors or drums need resurfacing or replacing depends entirely on their condition at the time the brakes are relined.

Even so, many mechanics prefer to resurface rotors and drums when relining the brakes to restore the friction surfaces to "like-new" condition and to minimize any chance of brake squeal.

Repair Guide: Brake System Basics

2008-01-31T07:54:00.000-08:00

Braking action begins when the driver pushes on the brake pedal. The brake pedal is a lever, pivoted at one end, with the master cylinder push rod attached to the pedal near the pivot point. With this lever arrangement, the force applied to the master cylinder piston through the push rod is multiplied several times over the force applied at the brake pedal.

The bracket is mounted to the inside of the engine compartment cowl or firewall. The master cylinder push rod that connects the pedal linkage to the master cylinder goes through a hole in the firewall.

The master cylinder is mounted on the opposite side of the firewall in the engine compartment. If the car has manual brakes, the cylinder will be mounted directly to the firewall. If a power booster is used, it will be mounted to the firewall and the cylinder is mounted to the booster.

Question:

How do I know when my car really needs a brake job?
Answer:

You need a "brake job" when your brake linings are worn down to the minimum acceptable thickness specified by the vehicle manufacturer or the applicable state agency in areas that set their own requirements. The only way to determine if new linings are required, therefore, is to inspect the brakes.
You may also need a brake job if you're having brake problems such as grabbing, pulling, low or soft pedal, pedal vibration, noise, etc., or if some component in your brake system has failed. But if the problem is isolated to only one component, there's no need to replace other parts that are still in perfectly good working order.

There is no specific mileage interval at which the brakes need to be relined because brake wear varies depending on how the vehicle is driven, the braking habits of the driver, the weight of the vehicle, the design of the brake system and a dozen other variables. A set of brake linings that last 70,000 miles or more on a car driven mostly on the highway may last only 30,000 or 40,000 miles on the same vehicle that is driven mostly in stop-and-go city traffic.

As a rule, the front brakes wear out before the ones on the rear because the front brakes handle a higher percentage of the braking load -- especially in front-wheel drive cars and minivans. So many service facilities advertise $59.95 brake job "specials" that replace the linings on the front brakes only. Doing the front brakes only is okay and can save you money as long as the rear brakes are in good condition. But if the rear brakes need attention, they should be relined too.

One of the problems with the brake specials you see advertised in the newspaper is that the price is very misleading. A person typically goes in expecting to spend $59.95 for a brake job, but usually ends up spending considerably more because the brakes need more than the minimum amount of work to restore them to like-new condition. The price of a brake job depends entirely on the work that needs to be performed. So any advertised special is not a firm price, but only an estimate of the least amount of money it might cost you to get your brakes fixed. A price should not be quoted until after the brakes have been inspected. Then and only then can an accurate determination be made of the parts that actually need to be replaced.

Question:

What parts are generally replaced during a brake job, and why?
Answer:

A traditional brake job (if there is such a thing) usually means replacing the front disc brake pads, resurfacing the rotors, replacing the rear drum brake shoes, resurfacing the drums, bleeding the brake lines (replacing the old brake fluid with new and getting all the air out of the lines), inspecting the system for leaks or other problems that might require additional repairs, and checking and adjusting the parking brake.
Some brake jobs may also include new hardware for the drums (recommended), and rebuilding or replacing the wheel cylinders and calipers (also recommended). But because of the added expense, these items may not be included in the package price or may only be done if the brake system really needs them (as opposed to doing them for preventative maintenance).

Hardware includes things like return springs, hold down springs and other clips and retainers found in drum brakes. It may also include bushings, pins and clips on disc brake calipers. Springs lose tension with age and exposure to heat. Most experts recommend replacing the hardware when relining drum brakes to restore proper brake action. If weak springs are reused, the shoes may drag against the drums causing accelerated shoe wear, a pull to one side, brake overheating and possible drum damage. Other hardware that is badly corroded or faulty (such as the self-adjusters) may prevent the shoes from maintaining the correct drum clearance (which increases the distance the brake pedal must travel as the shoes wear), or the parking brake from functioning properly.

It's important to note that not all replacement linings are the same. There are usually several grades of quality in pads and shoes (good, better and best). The difference is in the ingredients that are used to manufacture the pads and shoes. The less expensive ones may cost less initially and save you a few dollars on your total bill, but you may not be happy with the way they wear and perform. All brake linings must meet minimum government safety standards. Even so, the cheaper grade of pads and shoes do not last as many miles as the premium grade of replacement linings, nor do they brake as effectively. They usually have a greater tendency to fade at high temperature and may increase the vehicle's stopping distance somewhat. Noise may also be a problem with cheap linings. The best performance and value for your money, therefore, is with the best or premium grade. Choose these when the brakes are relined.

Repair Guide: Brake Rotors and Pads

2008-01-31T07:53:00.000-08:00

Repair Guide: ABS, Antilock

2008-01-31T07:51:00.000-08:00

If the brakes are applied too hard when driving on slippery road surfaces, they may lock up or stop the wheel. The wheel then loses frictional contact with the road and skids and the vehicle is no longer under control. Experienced drivers know that the way to prevent lock-up is to pump the brake pedal up and down rapidly.

Many late-model cars are now equipped with an antilock brake system (ABS). The antilock brake system does the same thing as an experienced driver. It senses that a wheel is about to lock-up or skid and it rapidly interrupts the braking pressure to the brake system at that wheel.

The brains behind the antilock brake system is the computer, which monitors system operation at all times. It processes information from the wheel sensors and determines wheel speed. From this information, the electronic controller can determine whether one wheel is turning slower than the other wheels.

The computer gets its information on wheel speeds from wheel sensors located on each wheel. Each sensor assembly consists of a magnetic pickup sensor and a toothed sensor ring. The front sensor rings are attached to the back side of the rotor assembly. The rear sensor rings are attached to the axle shaft. The pickup assemblies are bolted to brackets at each wheel.

The wheel sensors are essentially magnetic pickup assemblies. Each pickup assembly consists of a permanent magnet with a coil of wire wound around it. The sensor is positioned extremely close to the sensor ring, which rotates as the wheel turns. As the teeth pass the pickup assembly, the signal is induced in the coil by electromagnetic induction as the magnetic field goes from strong to weak and back to strong. This signal change is used by the computer to determine wheel speed.

The antilock brake system uses a hydraulic control unit in place of the standard master cylinder. The hydraulic control unit consists of a master cylinder, a vacuum or hydraulic booster, electric pump, accumulator, a solenoid valve body assembly, and pressure control and warning switches.

The electric pump is a high pressure pump designed to run at frequent intervals for short periods of time. The pump fills the hydraulic accumulator and supplies high pressure brake fluid to the brake system.

The accumulator is a nitrogen gas-filled assembly used to store and supply pressure to the brake system. The accumulator is attached to the pump housing. The top chamber of the accumulator is filled with nitrogen gas. The bottom chamber contains brake fluid, which is supplied from the hydraulic electric pump. A diaphragm is used to separate the two chambers.

CAUTION: Do not disassemble any accumulator. The nitrogen gas contained in the accumulator is pressurized to 1,200 psi (8,274 kPa). Antilock brakes use extremely high pressure, so always follow service manual procedures when working on one of these systems.

During operation, the electric pump supplies brake fluid to the lower chamber of the accumulator, and the diaphragm moves upward, compressing the nitrogen gas in the upper chamber. The nitrogen gas, which is under pressure in the top chamber, then pushes down on the diaphragm, causing the brake fluid in the bottom chamber to be maintained at a very high pressure. During normal braking conditions (no antilock control), the accumulator supplies pressurized brake fluid to the booster and the rear brakes. During antilock braking conditions, the accumulator also supplies pressurized brake fluid to the front brakes. The accumulator can provide pressure required for a number of stops if the electric pump should fail.

The solenoid valve assembly is a set of electrically operated solenoid switching valves. The main solenoid valve opens a connection between the boost pressure chamber of the brake power booster and the internal master cylinder reservoir and closes the flow to the reservoir during antilock control. This provides a continuous supply of high pressure brake fluid during antilock control to replace the fluid being allowed back to the reservoir. When antilock control stops, the main valve closes and the return to the reservoir is reopened. By closing the main valve, accumulator pressure is removed from the front brake circuits within the master cylinder.

A set of smaller solenoid valves is located in a solenoid valve body. The valve body contains three pairs of electrically operated solenoid valves: a pair for each of the front brakes and a pair that controls both back brakes together. Each pair contains a normally open inlet solenoid valve and a normally closed outlet solenoid valve. During normal braking conditions (no antilock control), brake pressure is supplied to the brakes through the inlet solenoid valves upon brake application.

The computer determines the rotation speed of each wheel. If it senses a possible wheel lock-up, it goes into the antilock function and then applies voltage to the appropriate solenoid valves. When the system goes into antilock control, the computer will open and close the appropriate inlet and outlet solenoid valves, which control the operation of any of the brakes on any of the four wheels and prevent wheel lock-up. When the system is in antilock brake operation, the brake pedal will pulsate at an extremely fast rate. Pressure control and warning switches warn the driver of any malfunction in the system.

Question:

I feel a pulsation or vibration in my brake pedal every time I stop. But the brakes seem to work fine. Is anything wrong?
Answer:

A pulsating brake pedal, which may be accompanied by a shuddering or jerky stop during normal braking, usually means a warped rotor or an out-of-round drum -- although it can sometimes be caused by loose wheel bearings, a bent axle shaft or loose brake parts. If the vehicle is equipped with ABS, however, some pedal feedback and noise is normal during panic stops or when braking on wet or slick surfaces. But you should not experience any ABS pedal feedback when braking normally on dry pavement.
The faces of a disc brake rotor must be parallel (within .0005 inch on most cars) and flat (no more than about .002 to .005 inches of runout) otherwise it will kick the brake pads in and out when the brakes are applied, producing a pulsation or vibration that can be felt in the brake pedal as the rotor alternately grabs and slips.

You can often see warpage in a brake rotor by simply looking at it. If the rotor has telltale glazed or discolored patches on its face, chances are it is warped. Measuring it with a dial indicator and checking it for flatness with a straight edge will confirm the diagnosis.

Resurfacing the rotor to restore the faces will usually eliminate the pulsation (unless the rotor is bent or is badly worn and has started to collapse in which case the rotor must be replaced). But it may only do so temporarily because of metallurgical changes that take place in the rotor. Hard spots often extend below the surface of the rotor. Resurfacing will restore the surface, but the hard spot may reappear again in a few thousand miles as the rotor wears. For this reason, GM and others recommend replacing warped rotors rather than resurfacing them.

Pedal pulsation caused by drum warpage isn't as common, but it can happen. A drum can sometimes be warped out-of-round by applying the parking brake when the brakes are hot. As the drum cools, the force of the shoes causes the drum to distort.

What causes a rotor to warp? Overtorquing or unevenly torquing the lug nuts with an impact wrench is a common cause. For this reason, most experts recommend using a torque wrench to tighten lug nuts when changing a wheel. There are also special torque-limiting extension sockets called "Torque Sticks" that can be safely used with an impact wrench to accurately tighten lug nuts. But a plain impact wrench should never be used for the final tightening of the lug nuts because most provide no control whatsoever over the amount of torque applied to the nuts.

Overheating can also cause rotors to warp. Overheating may be the result of severe abuse or dragging brakes. Defects in the rotor casting, such as thick and thin areas can also cause uneven cooling that leads to warpage. Hard spots in the metal due to casting impurities can be yet another cause.

Question:

I've heard that using a temporary spare will disable my ABS system. Is that true?
Answer:

Yes. On many cars equipped with ABS and a temporary spare, an electrical connector inside the trunk or luggage compartment is attached to the valve stem on the spare tire. If you have a flat tire and remove the spare, you have to unplug the connector. This tells the ABS system that the temporary spare is being used, causing it to temporarily disable itself.
The reason why the ABS system shuts itself off when the temporary spare is in use is because the spare tire has a smaller diameter and narrower tread than a standard tire. This causes the tire to rotate somewhat faster than the other tires, and to brake differently. Were the ABS system not disabled, the difference in wheel speed and braking friction caused by the temporary spare would probably cause the ABS system to kick in unnecessarily when the brakes are applied. So disabling the ABS system prevents this from happening.

The important thing to remember here is to reconnect the ABS connector to the spare tire when it is returned to the trunk. If this is not done, the ABS system will remain disabled and unable to prevent skidding when braking on wet or slick surfaces.

Question:

When I replace the tires on my vehicle, do I have to use the same size as the originals?
Answer:

On ABS-equipped vehicles, all vehicle manufacturers recommend using the same size and aspect ratio tire as the original. ABS systems monitor the rotational speed of the tires through individual wheel speed sensors. Changing to an oversize tire with a taller diameter than stock would cause the tires to rotate at a slightly slower speed relative to vehicle speed than the stock tires. Changing to a low profile tire with a shorter diameter would cause the tires to rotate at a slightly faster speed relative to vehicle speed. Though the difference either way isn't much, it may be enough to upset the calibration of the ABS system and have an adverse effect on its ability to detect and prevent skids.
Another reason for not changing tire sizes is because it can affect the speedometer, odometer and transmission shift points on a vehicle with an electronic automatic. Oversize tires will make your speedometer read slower than normal (which may get you a speeding ticket unless you have the speedometer recalibrated to compensate for the change in tire size!). Smaller diameter tires will make the speedometer read faster than normal, and increase the mileage readings on your odometer at a faster than normal rate.

All this doesn't mean you can't change tire and wheel sizes, however. If you maintain the same overall tire diameter as before, you can switch to larger wheels with a shorter aspect ratio tire. This is the basic idea behind "Plus 1, Plus 2" tire and wheel sizing.

Replacing a stock 14-inch wheel and 70 series tire with a 15-inch 60 series tire would be Plus 1. Plus 2 would be moving up to a 16-inch wheel and possibly a 50 series tire. Plus 3 would be going to the new 17-inch tire and rim combination -- which could turn out to be a Plus 4 application if the vehicle originally had 13-inch wheels.

ASPECT RATIO

The "aspect ratio" of a tire is the ratio of its section height to its section width. The smaller the number, the shorter the sidewall and the wider the tire. Low aspect ratio tires started with 60 series some time ago, then progressed to 50 series and now 45, 40 and even 35 series tires.

Shorter aspect ratio tires (60 and less) are usually considered to be performance tires because they lower vehicle ride height, have a wider tread and put more rubber on the road to improve handling. But the shorter the sidewall, the harsher the tire rides.

A tire's ability to support a given load depends on its air volume. If you go to a lower aspect ratio tire with a shorter sidewall, the tire must be wider to maintain the same air volume. If you just go to a shorter aspect ratio tire without increasing width, the load carrying capacity goes down. That's why when you go from a standard wheel to a Plus 1 wheel, the rim is usually wider to accommodate a wider tire.

It's important to follow the tire manufacturer's recommendations as to load capacities when going to larger wheel and tire sizes. There's no hard rule that says you have to drop 10 points in aspect ratio when increasing wheel size one inch, but that's the general recommendation.

Under hood Maintenance: Windshield Washers and Wipers

2008-01-30T14:01:00.000-08:00

Wiper Blades

The windshield wiper system is another area that requires periodic service. The wiper blades are inspected and replaced when they are worn out. The windshield washer fluid reservoir is inspected and refilled when it is low. The technician who performs these services should have a basic understanding of how the system works.

An electric wiper motor, located under the cowl panel, provides the power for the system. When the wiper switch is turned on, the motor begins to move a linkage system back and forth. This motion is transferred to a set of wiper arms on the outside of the windshield. Wiper blades attached to the arms move back and forth across the windshield.

When the windshield needs washing, the driver can turn the wiper switch to activate the washer system. The washer system consists of a reservoir, pump, hose, and washer nozzle. The reservoir contains windshield washer fluid. An electric pump in the reservoir pumps cleaning fluid out of the reservoir through a hose to the washer nozzle. The nozzle is located below the windshield and directs a spray on the windshield. When the washer is activated, the wipers are also activated so the wiper blades move the fluid across the windshield to clean it.

The windshield washer fluid reservoir is a plastic bottle. The reservoir is located under the hood in the engine compartment. The level of washing fluid can be observed through the container. Washer fluid is available in containers from automotive parts stores. Always check the owner's manual for the recommended type of fluid.

The wiper arm is attached to the linkage from the wiper motor. The wiper blade assembly is the part that contacts the windshield. It has a metal support that holds a rubber wiper blade. The support holds the rubber blade in the proper position against the windshield.

Inspect and Refill Windshield Wiper Fluid

The windshield washer system must have enough windshield washer fluid to properly clean the windshield. Anytime you service the windshield wipers or are under the hood, inspect and refill any lost windshield wiper fluid.

Windshield washer fluid is available in automotive parts stores. The fluid is often colored blue so that it is easy to see in the washer system reservoir.

Open the hood and locate the washer reservoir Typically, the reservoir is transparent so the fluid can be seen through the reservoir. Inspect the fluid level. Some reservoirs have a "full" line, but most are filled all the way to the top. If the level is low, remove the cap on top. Place a clean funnel in the cap opening and pour in the washer fluid until it reaches the correct level.

WARNING: You will need to add windshield washer antifreeze to prevent the washer fluid from freezing in cold weather conditions.

WARNING: Never use dirty fluid or a dirty funnel in a washer system. Dirt in the system can clog the tiny jets that spray the fluid on the windshield.

Remove and Replace a Windshield Wiper Blade

The rubber wiper part of a windshield wiper blade deteriorates from contact with sun and smog. It wears from contact with the windshield. Worn windshield wiper blades will not properly wipe the windshield. They could create a safety hazard for a driver in bad weather. A wiper blade can get so worn that the rubber part separates from the metal part. The metal part could then scratch the windshield when the wipers are turned on. Consequently, the wipers should be inspected regularly and replaced as necessary.

Worn wiper blades may be replaced in two ways. You can buy an entire wiper blade assembly or just a rubber insert . The insert is less expensive and a good choice for a newer car. The wiper assembly is a good choice on an older car in which the metal wiper parts are corroded or damaged.

To replace either the blade assembly or just an insert, remove the blade assembly from the wiper arm. There are many types of retaining systems used between the arm and blade. The most common is the release lever. You release the arm from the blade by lifting up on the tiny release lever.

Often the insert is held with spring clips called bridge claws or lock tabs. A button may have to be pushed to disengage some types. You will have to squeeze or pinch other parts to release the lock tabs.

Be careful not to lose the small parts during disassembly and reassembly. Always compare the replacement parts with the new ones. When you have installed the new blade assemblies or inserts, test the system. First clean all dirt or dust from the windshield. Pour water on the glass and turn on the wipers. Check to see that they do a good job wiping the water.

WARNING: Never operate wipers on a dry or dirty windshield. The blades could rub the dirt over the windshield and cause scratches.

SERVICE TIP: Never disassemble both wiper assemblies at the same time. Do one at a time and use the assembled unit as a guide for correct assembly.

Question:

How often should I replace my wiper blades?
Answer:

Wiper blades are one of the most neglected components on vehicles today. Many blades are cracked, split, torn, brittle, worn or otherwise in obvious need of replacement. Others may look okay, but do a lousy job of wiping when put to the test.
Ninety percent of all driving decisions are based on a clear unobstructed view of the road, which means good visibility is absolutely essential -- especially during wet weather when vision may be obscured by water, road splash, sleet or snow on the windshield. But good visibility requires wipers that are in good condition. If the wipers are chattering, streaking or otherwise failing to wipe cleanly and consistently, you need new blades -- NOW!

Most experts say wiper blades should be replaced every six to twelve months for optimum performance and driving visibility. That's because wiper blades don't last forever. Natural rubber deteriorates over time. Halogen-hardened rubber as well as synthetic rubber provides longer life. But eventually all blade materials fall victim to environmental factors. Exposure to sunlight and ozone causes the rubber to age, even if the wipers aren't used much.

As a set of blades age, they lose much of their flip-over flexibility and they're less able to wipe cleanly. They may develop a permanent set (called "parked" rubber) or curvature which prevents full contact with the windshield. This tends to be more of a problem on vehicles that are parked outside in the hot sun all day. The sun bakes and hardens the rubber. Then when the wipers are needed, they streak and chatter because they've taken a set and won't follow the curvature of the windshield. It can be very annoying as well as dangerous.

Cold weather can affect blade life, too. Freezing temperatures makes rubber hard and brittle, which increases the tendency to crack and split. The holders can also become clogged with ice and snow, preventing the holder from distributing spring tension evenly over the blade. The blade "freezes up" and leaves streaks as it skips across the glass.

Heavy use can be hard on wiper blades, too, because dust, abrasives, road grime and even bug juice wear away the edge that the blades need to wipe cleanly. As the blade loses its edge (which is precision cut square to maximize the squeegee effect), water gets under the blade and remains on the glass. The result is reduced visibility and poor wiping action.

Any blade that's chattering, streaking or doing a lousy job of wiping, therefore, is a blade that's overdue for replacement. The same goes for any blade that is cracked, torn, nicked or otherwise damaged.

CHECKING YOUR BLADES

A simple check is to try your windshield washers. If the blades are not in good condition, you'll see why when they attempt to wipe the washer solvent off the glass. Streaking, chattering or any other problems will be clearly obvious.

This test also gives you the opportunity to check your windshield washer system. Do both squirters work? If not, a nozzle may be plugged with dirt or a hose may be kinked or loose. Does the spray hit the windshield where it is supposed to? If not, the nozzles need adjusting. Does the washer pump deliver an adequate stream of solvent? If not, the vehicle may have a weak washer pump, or a clogged, kinked or loose hose. Most washer reservoirs have a screen to filter out debris that could clog or damage the pump. If this screen itself is buried under debris, it can choke off the flow of solvent to the washers.

After you've checked the windshield wipers, check the rear wiper too if your vehicle has a rear wiper system. Many sport utility vehicles, vans, minivans, station wagons, hatchbacks and fastbacks do. After all, it's just as important to see what's behind you when backing up in the rain as it is to see what's ahead. You can use the same test (try the rear windshield washer, if so equipped), or simply spray some water onto the glass with a squeeze bottle and see how the wiper performs.

OTHER FACTORS THAT AFFECT YOUR WIPERS

How well the wiper blades perform also depends on the condition of the wiper arms and holders. A blade's wiping ability is affected by the amount of spring tension on the wiper arm, the number of pressure points or claws that hold the blade, and the design of the blade itself. If the springs in the arms are weak (which is more apt to be a problem in older vehicles), the wipers may not be pressed against the glass firmly enough to wipe cleanly. Replacing the blades won't make any difference because the problem is weak arms not bad blades.

If the blades can be pulled away from the glass with little resistance, it's time for new arms. Most vehicle manufacturers publish tension specs for their arms. If the arm doesn't meet the spec, it needs to be replaced.

Remember to check the tension on the rear wiper arm, too, because rear wiper arms are often damaged by drive-through car wash rollers.

Wind lift is another factor that can interfere with good wiping action at highway speeds. Many windshields are steeply sloped to improve aerodynamics. But steeply raked windshields with a lot of glass area direct more wind against the wipers. This can lift the blades away from the glass at high speed unless the wiper system and blades are designed to counter the aerodynamic forces. Some blades have specially designed vents and airfoils to minimize lift and/or generate downforce to keep the blades in constant contact with the glass as speed increases. If your original equipment blade holders need to be replaced, be sure the replacements have the same anti-wind lift design.

Another factor to keep in mind is the design of the blade holder. A blade holder needs to distribute the tension of the wiper arm evenly over the blade while also allowing the blade to flex as it follows the changing curvature of the glass. The better quality replacement blade holders typically have six to eight claws to spread the pressure of the wiper arm over the blade. More claws also increases flexibility so the blades don't lose contact at the sides of the glass.

REPLACEMENT BLADES

You can usually replace wiper blades yourself, and can replace just the blade with a refill or the entire blade assembly. Refills will save you money. If you're installing a blade assembly, most come with some type of adapter to fit the arms on your vehicle. The old blades pull or push off the arm by pressing a release button or pin on the wiper holder.

If you are replacing the blade only with a refill, the old blade can be removed by squeezing the locking tags in at the end of the blade so it will slip out of the holder. Make sure the replacement blade is the same length and claw width as the original. A blade that is too long may create interference problems, while one that is too short may not fit the holder.

For cold weather driving, you might consider installing a set of "winter blades" on your vehicle. These have an enclosed holder that prevents ice and snow from building up and interfering with the wiper's ability to do its job.

Under hood Maintenance: Transmission Oil/Fluid

2008-01-30T13:58:00.000-08:00

Check Manual Transmission Lubricant Level

The manual transmission is lubricated by a lubricant that is splashed throughout the transmission by the moving gears. The lubricant must be at the correct level or the transmission parts could wear out in a very short time. The interval for lubrication level check is specified in the maintenance schedule in the owner's manual. Most technicians make this check whenever the car is up on a hoist for an undercar inspection.

Some imported cars have a dipstick to check manual transmission fluid level. This dipstick is found under the hood. The engine must be off to check the fluid with a dipstick. Remove and wipe the dipstick with a clean rag. Then insert the dipstick back into position. Remove it again and note the reading. Lubricant must be between the "full" and "add" marks on the dipstick. When you are done, replace the dipstick.

CAUTION: Make manual transmission checks with the engine off. Never put your finger into a transmission fill plug hole. If the drive wheels are turned, your finger could be caught in the gearing.

WARNING: A car that is not level on a hoist or jack will not show a true lubricant level in the transmission. If the engine has been running, allow two or three minutes before checking for a more accurate reading.

You will have to check most cars up on the hoist or jack. Raise the car and be sure it is level. Locate the transmission fill plug on the side of the transmission. You may have difficulty locating it. If you do, look for an identification diagram like the one shown below. Do not confuse the fill plug with the drain plug, which is located at the bottom of the transmission.

Clean the area around the fill plug to avoid getting dirt into the transmission. Remove the fill plug with the correct size wrench. If the transmission is full, you may see lubricant begin to leak out of the fill plug hole. If this happens, replace the plug.

You will probably find that the lubricant level is below the level of the fill plug hole. Bend a short length of metal wire and insert it into the fill hole. Pull the wire out and note the lubricant on the end of the wire. The lubricant level should be very close to the level of the fill plug.

If the lubricant level is satisfactory, replace the fill plug. If the level is low, add lubricant as explained in the next section.

Drain and Refill Manual Transmission Lubricant

The car manufacturer specifies regular time and or mileage intervals for the changing of manual transmission lubricant. You can find this information in the owner's or shop service manual. You will also need to look up the type and quantity of lubricant required. A lubricant chart can usually be found in a shop manual.

WARNING: Manual transmissions for different cars use many different types of lubricants. These include engine oil, automatic transmission fluid, and gear lubricant. Always determine and use the correct lubricant type. The incorrect lubricant can cause major damage to the transmission.

Drive the car long enough to heat up the lubricant. Lift the car on a hoist or jack and jack stands. The car must be level for accurate refilling of the transmission. Locate the drain and fill plug on the transmission as described in the previous section.

CAUTION: Be careful when draining a transmission because the oil could be hot enough to cause burns.

Position a clean drain pan under the drain plug. Clean around the area of the fill and drain plug. Remove the drain and fill plugs and allow the transmission to drain.

Inspect the fluid that collects in the drain pan. Look for metal in the oil. Metal shows up as shiny, metal particles or flakes. An excessive amount of metal could mean internal damage to transmission components.

When the lubricant is completely drained, clean the drain plug. Replace any sealing washer or use the recommended type of sealant on the drain plug threads. Install the drain plug and tighten it to the recommended torque.

The new lubricant will need to be pumped into the transmission through the fill plug hole. There are two types of lubricant pumps. Small hand pumps that attach to the container of lubricant are available at auto parts stores. Larger containers hold several gallons of lubricant. These have a hand pump that forces the lubricant through a hose and out a nozzle.

Place the delivery nozzle from the pump into the fill plug hole. Slowly pump the lubricant into the transmission. Stop pumping a few seconds after each pump to give the lubricant time to flow to the bottom of the transmission. Stop filling when the lubricant reaches the bottom of the fill plug hole. Wait several minutes, then check the level again. Sometimes the level will drop as the lubricant settles to the bottom of the transmission. Install the fill plug and wipe away any spilled fluid.

Check Automatic Transmission/Transaxle Fluid Level and Condition

Automatic transmission or automatic transaxle fluid should be checked at regular mileage and time intervals as specified in the owner's manual. Anytime you are doing lubrication work on a car you should check the fluid level.

Make sure the engine and transmission are up to operating temperature. Locate the fluid level checking procedure in the owner's or shop service manual. Drive the car onto a level surface. Most cars must have the engine running to make a fluid level check. Some cars must have the transmission in NEUTRAL and others require that it be in PARK for testing. Set the selector in the correct mode. If the transmission is checked in NEUTRAL, block the wheels and set the parking brake.

WARNING: Failure to have the transmission in the correct gear when checking fluid level can cause a large error in the reading.

Raise the hood and locate the automatic transmission/transaxle dipstick. Typically you will find the dipstick near the transmission end of the engine at the opposite end of the drive belts.

WARNING: Never wipe a dipstick with a rag with lint. Lint from a rag could get into transmission control valves and cause them to stick. It could also plug up fluid passages. Use only lint-free rags or shop towels.

Remove the dipstick and wipe it with a clean, lint-free rag. Observe the markings on the dipstick. There is no standard marking system, so you may need to look up an explanation of the marks in the owner's manual. A typical marking system is shown below. This dipstick has a full hot level mark and an add 1 pt (pint) or 0.5 L. (liter) mark. The word hot means the fluid must be hot when checked. There can be a large difference in fluid level between hot and cold fluid levels. Some dipsticks have a cold reading on the dipstick, which should be used if the transmission is cold.

Insert the dipstick back into its housing and push it down until it seats. Pull it back out and observe the fluid level in relation to the dipstick markings. If fluid must be added, refer to the section on adding fluid.

While you have the fluid on the dipstick you should observe its color and condition. This information can help you decide if the fluid requires changing. Clean, uncontaminated fluid has a pinkish or reddish color. Fluid that has been overheated turns a darkish brown or black. A white milky appearance can mean that the engine coolant is leaking into the transmission.

Another fluid check to make is to wipe the fluid off the dipstick with a white absorbent paper. Look for foreign particles in the fluid. Silvery particles can mean there is wear on metallic parts. Dark particles can be friction material that has come off transmission parts. Also look for a dark gummy material on the dipstick. This is usually a varnish buildup in the fluid. Fluid that shows any of these problems should be changed, as explained in the following section. Replace the dipstick and make sure it is seated properly.

Drain Fluid, Change Filter, and Refill Automatic Transmission/Transaxle Fluid

The fluid in an automatic transmission or automatic transaxle has many important jobs to perform. All of these depend on the fluid being clean and in good condition. Fluid should be changed if your dipstick test shows any of the problems described previously. Fluid should also be changed at the regular time and mileage interval specified in the owner's manual.

The first step in fluid changing is to get the transmission/transaxle up to normal operating temperature. The contaminants in the fluid will flow out better when the fluid is warm.

Raise the car on a hoist or support it on a jack and safety stands. Place a large drain pan under the transmission area. Some transmissions have a drain plug. If the car you are working on has one, use the correct size wrench to remove it as shown below.

CAUTION: Wear eye protection when draining a transmission/transaxle to protect your eyes against hot fluid splash. Be careful not to spill hot fluid on yourself.

Many transmissions do not have a drain plug. In these cases the manufacturer wants the technician to remove the pan and to change the fluid filter. To remove the oil pan, first remove any parts that interfere with the oil pan being removed. Use the correct size wrench to loosen but do not remove all the pan bolts. Remove all the bolts except the ones on one end. These bolts will keep the pan from falling off while the fluid drains. Make sure your drain pan is in position. Gently tap the pan with a rubber mallet to get it to break free of the transmission.

WARNING: Never use any tool to pry between the pan and the transmission/transaxle sealing surface. If you damage this surface, the transmission pan may not seal properly and will leak.

Allow the transmission to drain. Then remove the remaining bolts and the pan. Carefully check the bottom of the pan for foreign material. The material that collects in the pan is a good indicator of the transmission condition. A small amount of deposits from friction and metal parts is normal. A buildup of particles of metal or friction material is a sign of transmission wear.

Carefully remove the old gasket from the pan. Do not use any sharp tool to scrape the gasket or the sealing surface could be damaged. Use a lint-free rag to clean the pan.

Now you are ready to change or clean the fluid filter or screen. The filter or screen is mounted on the bottom of the valve body assembly as shown below. The filter or screen works like the oil filter in the engine. It cleans the fluid being pumped into the transmission parts from the pan. The filter or screen must be changed or cleaned each time you change the fluid.

WARNING: Before removing any filter or screen, check the procedure in a shop service manual. Some transmissions use the screen or filter to hold some small check valves and springs in position. These valves can fall out if the filter or screen is not carefully removed.

Filters and screens are often held in place with several screws. These screws may be regular Phillips or hex head or special torx head type. Use a torx head screwdriver to remove these screws. Some screws may be longer than others. Be careful to note size differences so you can reinstall them in the correct position.

There are two basic types of filters. One type is made from paper or cotton. This type is made to be replaced. The screen type has a metal screen with a washable filter element inside. This type is made to be cleaned and reused. Wash the replaceable screen with recommended solvent or spray cleaner and air dry.

When you are ready to reassemble, place the new pan gasket and filter next to the old ones. They will match up if they are the correct parts. Install the new filter or cleaned screen on the valve body and tighten all the fasteners to the correct tightening specifications.

Place the new gasket on the sealing surface of the fluid pan. Check the shop service manual for recommendations regarding any sealant to be used on the gasket. Also look up the pan bolt tightening sequence and the required torque. Place the pan and gasket in position and start all the screws. Use the correct type torque wrench to tighten the bolts in the correct sequence and correct torque.

WARNING: Some pan tightening specifications call for the use of an inch-pound torque wrench. Do not confuse these specifications and use a foot-pound torque wrench. Mixing up these specifications could cause the part to be over-tightened and damaged.

Most late model cars do not require that the torque converter be drained. Although there are no drain plugs on most late-model torque converters, some older cars do have them. Torque converter drain plugs are often found by removing an access cover on the bottom of the torque converter housing. The engine then has to be cranked until the drain plug on the torque converter appears in the access hole as shown below. Then follow the procedure for draining the fluid.

When you have finished your work underneath the car, lower it to the floor. You will need the specifications from the owner's or shop service manual on the type and amount of fluid to add to the transmission/transaxle. Some specifications list the amount of fluid required for a pan draining and a larger amount if the torque converter is drained. Be sure not to confuse these amounts.

WARNING: Use only the recommended type of fluid. Using an incorrect fluid type can damage some transmission friction parts.

Open the hood and remove the transmission/transaxle dipstick. Install a clean funnel in the dipstick and filler tube. Open and pour the recommended amount of fluid into the transmission/transaxle through the funnel. Remove the funnel and replace the dipstick.

Start the engine and allow the engine and transmission to warm up to operating temperature. With your foot on the brakes and the parking brake set, move the gear selector through each of the gear selections. Doing this allows the fluid to circulate through the entire transmission. Place the transmission in the correct gear for fluid checking and recheck the fluid level with the dipstick. Correct the fluid level if necessary. Test drive the car and check for proper transmission/transaxle operation.

WARNING: The fluid level is critical to proper transmission/transaxle operation. Too high a fluid level can cause rotating parts in the transmission to whip the fluid up and cause air bubbles. Air in the fluid can cause transmission slippage. Low fluid level can also cause air in the fluid and erratic transmission operation.

Under hood Maintenance: Power Steering Fluid

2008-01-30T13:57:00.000-08:00

Most cars today are equipped with a power steering system. Many power steering systems use hydraulic power. These systems use a power steering pump driven by a belt from the crankshaft. The pump moves fluid under pressure through hoses to the steering gear. The pressure is used in the steering gear to reduce steering effort. A reservoir for fluid is attached to the rear of the pump. Checking the fluid level in this reservoir is a common underhood maintenance job.

The fluid in the power steering system provides lubrication as well as the power assist. Low fluid level can cause a lack of power assist, excessive noise, and rapid part wear. The power steering fluid level should be checked at regular intervals.

CAUTION: Check the fluid level with the engine off to prevent possible injury from moving parts.

The fluid is checked at the pump reservoir with a dipstick attached to the reservoir cap. . Before removing the reservoir cap, wipe the outside of the cap and reservoir to prevent dirt from falling into the reservoir. Pull the dipstick out and note the fluid reading. The fluid should be between the "hot" and "cold" mark on the dipstick. There are hot and cold marks because the fluid expands as it gets hot. If the level is below the "add" mark, you will have to add fluid to bring it up to the correct level. You should use only the type of fluid listed in the owner's or shop service manual. Older cars use automatic transmission fluid. Special power steering fluids are used on late-model cars. Add the correct amount of fluid and replace the dipstick.

Q & A: Power steering fluid

Question:

1. My power steering feels stiff when I first start my car, but then feels normal after I've driven the car awhile. How come?
Answer:

This is called "morning sickness" and has nothing to do with being pregnant. The condition is caused by wear in the spool valve housing on certain power steering racks -- notably GM front-wheel drive cars.
When the car is first started, the rack is cold and clearances in the spool valve are at their greatest. Hydraulic pressure from the power steering pump leaks past grooves worn in the aluminum spool valve housing. This causes a loss of pressure and increases steering effort. The steering feels stiff with little or no power assist. As the car is driven, the rack warms up. This decreases the clearances inside the spool valve housing, which reduces the leakage past the grooves. More pressure goes to where it is supposed to go and the steering becomes easier as power assist returns.

The "fix" for this condition is to replace the rack with a new one (preferably with a cast iron spool valve housing) or a remanufactured rack that has a stainless steel sleeve pressed into the aluminum housing.

Question:

2. Does the power steering fluid ever need to be changed?
Answer:

Not normally, but it should be if the steering rack or pump are ever replaced. Under normal circumstances, the fluid in the power steering system should last the life of the vehicle (or the life of the major power steering components, whichever comes first). But as the system accumulates miles, microscopic particles of metal and rubber can buildup in the fluid. These particles can act like an abrasive and accelerate pump and gear wear, so the fluid should be changed if the original pump or rack has failed to prevent contaminating the new parts with dirty fluid.

CHECK PERIODICALLY

Even though the fluid in your power steering system does not normally require changing, it's a good idea to check the fluid level periodically (say once a month or when changing the engine oil and filter).

If the level is low, add fluid as needed to bring it up to the full level (hot or cold). Then inspect the hoses, pump and steering gear for leaks. More than a few ounces of fluid in the rubber bellows of a power steering rack indicates internal wear and leakage.

Always use the type of fluid specified by the vehicle manufacturer (Dexron II or a special blend of power steering fluid).

Under hood Maintenance: Engine oil

2008-01-30T13:51:00.000-08:00

Question:

My engine uses about a quart of oil every 1,000 miles. Should I be concerned?
Answer:

Not if you plan to sell or trade your vehicle soon. An engine that uses a quart of oil every 1,000 miles is starting to show the effects of wear. The amount of oil it is using is still acceptable, but it will gradually increase as the miles add up. When it reaches the point where it's using a quart every 500 miles or less, it's time for an overhaul.
Oil consumption depends primarily on two things: the valve guides and piston rings. If the valve guides are worn, or if there's too much clearance between the valve stems and guides, or if the valve guide seals are worn, cracked, missing, broken or improperly installed, the engine will suck oil down the guides and into the cylinders. The engine may still have good compression, but will use a lot of oil.

An oil consumption problem caused by worn valve guides can usually be cured by a valve job. Knurling or replacing the guides or boring out the guides and installing valves with oversized stems will stop the loss of oil.

Oil can also get past the rings if the rings or cylinders are badly worn or damaged, if the cylinders were not honed properly when the engine was built (or rebuilt), or if the rings were installed improperly.

When a newly-built engine is first started, the rings require a certain amount of time to "seat" or break-in. If the rings fail to seat properly, the engine will use oil. This may be the case if somebody applied the wrong finish to the cylinders, failed to clean and lubricate the cylinders properly before the engine was fired up, or didn't use the proper break-in procedure.

If the rings and/or cylinders are at fault, the engine will have lower than normal compression readings.

In some instances, worn rod bearings, excessive bearing clearances and/or excessive oil pressure can splash too much oil on the cylinders causing oil to get past the rings.

The cure for worn rings and cylinders is to overhaul the engine block. The cylinders have to be refinished and new rings installed to regain good oil control.

Question:

My engine is leaking oil past the valve cover gaskets. I've tried tightening down the valve cover bolts, but it doesn't seem to help. What should I do?
Answer:

Bite the bullet and buy a new set of valve cover gaskets. Most cork valve cover gaskets usually cost less than $20 and are fairly easy to install on many engines. You may have to disconnect and remove some plumbing or other accessories to get to the valve covers, but on many engines the job is usually within the capabilities of a do-it-yourselfer. If the valve covers are buried or access is difficult, then let a professional replace the gaskets for you.
Tightening the valve cover bolts or screws will rarely stop an oil leak because the gasket is usually cracked, crushed or has lost its natural elasticity. Cork gaskets only last about four to six years before they age harden, become brittle and start to leak. Molded silicone rubber gaskets, on the other hand, (which are used on many late model domestic and import engines) often last the life of the engine. But molded rubber gaskets are a lot more expensive than die cut cork gaskets. That's why cork gaskets have long been used by the vehicle manufacturers.

Some engines do not have gaskets, but instead use a rubbery-glue called "RTV silicone sealer (the "RTV" stands for Room Temperature Vulcanizing). If this is the case, you can remove the valve cover, scrape off all the old RTV, and either apply a fresh bead of RTV silicone sealer to the valve cover flange or head mating surface or install a conventional gasket.

CAUTION: Do not let any pieces of rubber or debris fall into the engine. Also, if you decide to use RTV sealer and your engine has an oxygen sensor (which almost all 1981 and later engines do), make sure the RTV sealer is the "low volatile" variety that is approved for use with oxygen sensors. Some types of RTV give off silicone vapor that can be sucked through the crankcase and contaminate the oxygen sensor.

Question: Is it better to maintain my engine's oil level at the full mark or wait until it reaches the "add" mark to add oil?

Answer: Most vehicle manufacturers say it's okay to wait until the level reaches the add mark to add oil. The add mark is typically one quart below the full mark on the dip stick.Considering that the crankcase capacity on most passenger cars today is only four quarts, running the engine 25% low on oil (one quart) may not be wise. Here's why.

Oil not only lubricates the engine's internal parts, but also helps cool the bearings. The total amount of oil in the engine, therefore, serves as a heat sink to help control heat. Under normal driving conditions, running a quart low probably doesn't make much difference in terms of bearing temperature or overall engine lubrication. But during extremely hot weather, when driving at sustained highway speeds and/or when towing a trailer, running a quart low may increase the risk of accelerated engine wear and/or damage.

The best advice, therefore, is to add oil whenever the dipstick reads low. Don't wait until it is down a full quart. If it needs half a quart, add half a quart to bring it back up to the full mark.

CAUTION: Do not overfill the engine. Adding too much oil can overfill the crankcase. As the crankshaft spins around, it can whip the oil into foam if the level is too high. This, in turn, can cause a drop in oil pressure and loss of lubrication to critical engine parts. Also, too much oil may cause leaks as the extra oil is forced past seals and gaskets.

Follow your vehicle manufacturer's guidelines for the type and viscosity of oil to use in your engine.

Question:

How often should I change my oil?
Answer:

Most vehicle manufacturers recommend changing the oil once a year or every 7,500 miles in passenger car and light truck gasoline engines. For diesel engines and turbocharged gasoline engines, the usual recommendation is every 3,000 miles or six months.
If you read the fine print, however, you'll discover that the once a year, 7,500 mile oil change is for vehicles that are driven under ideal circumstances. What most of us think of as "normal" driving is actually "severe service" driving. This includes frequent short trips (less than 10 miles, especially during cold weather), stop-and-go city traffic driving, driving in dusty conditions (gravel roads, etc.), and driving at sustained highway speeds during hot weather. For this type of driving, which is actually "severe service: driving, the recommendation is to change the oil every 3,000 miles or six months.

For maximum protection, most oil companies say to change the oil every 3,000 miles or three to six months regardless of what type of driving you do.

A new engine with little or no wear can probably get by on 7,500 mile oil changes. But as an engine accumulates miles, blow by increases. This dumps more unburned fuel into the crankcase which dilutes the oil. This causes the oil to break down. So if the oil isn't changed often enough, you can end up with accelerated wear and all the engine problems that come with it (loss of performance and fuel economy, and increased emissions and oil consumption).

OIL ANALYSIS

Truck fleets often monitor the condition of the oil in their vehicles by having samples analyzed periodically. Oil samples are sent to a laboratory that then analyzes the oil's viscosity and acid content. Oil is then burned in a device called a spectrometer that reveals various impurities in the oil. From all of this, a detailed report is generated that reveals the true condition of the oil.

Oil analysis is a great idea for fleets and trucks that hold a lot of oil. But most consumers would have a hard time justifying the cost. Having an oil sample analyzed typically costs $12 to $20 for the lab work and report. Most quick lube shops charge $16.95 to $19.95 for an oil change. So why spend your money on a report that will probably tell you your oil needs changing? Just change the oil every 3,000 miles and don't worry about it.

Regular oil changes for preventative maintenance are cheap insurance against engine wear, and will always save you money in the long run if you keep a car for more than three or four years. It's very uncommon to see an engine that has been well maintained with regular oil changes develop major bearing, ring, cam or valve problems under 100,000 miles.

WHAT ABOUT THE OIL FILTER?

To reduce the costs of vehicle ownership and maintenance, many car makers say the oil filter only needs to be replaced at every other oil change. Most mechanics will tell you this is false economy.

The oil filters on most engines today have been downsized to save weight, cost and space. The "standard" quart-sized filter that was once common on most engines has been replaced by a pint-sized (or smaller) filter. You don't have to be a rocket scientist to figure out that a smaller filter has less total filtering capacity. Even so, the little filters should be adequate for a 3,000 mile oil change intervals -- but may run out of capacity long before a second oil change at 6,000 or 15,000 miles.

Replacing the oil filter every time the oil is changed, therefore, is highly recommended.

An engine's main line of defense against abrasion and the premature wear it causes is the oil filter. The filter's job is to remove solid contaminants such as dirt, carbon and metal particles from the oil before they can damage bearing, journal and cylinder wall surfaces in the engine. The more dirt and other contaminants the filter can trap and hold, the better.

In today's engines, all the oil that's picked up by the oil pump is routed through the filter before it goes to the crankshaft bearings, cam bearings and valve train. This is called "full-flow" filtration. It's an efficient way of removing contaminants, and it assures only filtered oil is supplied to the engine. In time, though, accumulated dirt and debris trapped by the filter begin to obstruct the flow of oil. The filter should be changed before it reaches this point, which is why the filter needs to be replaced when the oil is changed.

If you wait too long to change the filter, there's a danger that it might become plugged. To prevent this from causing a catastrophic engine failure due to loss of lubrication, oil filters have a built-in safety device called a "bypass valve." When the pressure drop across the filter exceeds a predetermined value (which varies depending on the engine application), the bypass valve opens so oil can continue to flow to the engine. But this allows unfiltered oil to enter the engine. Any contaminants that find their way into the crankcase will be pumped through the engine and accelerate wear.

FILTER REPLACEMENT

If you do your own oil changes, make sure you get the correct filter for your engine. Follow the filter manufacturer's listings in its catalog. Many filters that look the same on the outside have different internal valving. Many overhead cam engines, for example, require an "anti-drainback" valve in the filter to prevent oil from draining out of the filter when the engine is shut off. This allows oil pressure to reach critical engine parts more quickly when the engine is restarted. Filters that are mounted sideways on the engine typically require an anti-drainback valve.

CAUTION: The threads on a spin-on filter must also be the correct diameter and thread pitch (SAE or metric) for your engine. If you install a filter with SAE threads on an engine that requires metric threads (or vice versa), you can damage the threads that hold the oil filter in place. Mismatched threads can also allow the filter to work loose, which causes a sudden loss of oil pressure that may ruin your engine!

CHANGING YOUR OWN OIL

Some people say it's best to change the oil when the oil is hot (like right after driving), while others say it makes no difference. CAUTION: Hot oil is thinner and runs out faster but can also burn you if you're not careful. In any event, avoid unnecessary skin contact with oil because oil is a suspected carcinogen (causes cancer).

Changing the oil when it is cold may take a bit longer because the oil will drain more slowly from the engine, but there's no danger of being burned. Also, most of the oil will have drained down into the oil pan when the engine has sat for a period of time, which means you'll actually get a little more of the old oil out of the engine than if you attempt to drain it while it is still hot.

Used motor oil should be disposed of properly. The Environmental Protection Agency does not consider used motor oil to be a hazardous chemical, but it can foul ground water and does contain traces of lead. The best way to dispose of used motor oil is to take it to a service station, quick lube shop, parts store or other facility for recycling. Your old oil will either be rerefined into other lubricants or petroleum products, or burned as fuel.

Do not dump used motor oil on the ground, down a drain, into a storm sewer or place it in the trash. Many landfills will not accept used motor oil even if it is in a sealed container because it will eventually leak out into the ground. If you can't find an environmentally-acceptable way to dispose of the stuff, maybe you shouldn't be changing your own oil. Service facilities that do oil changes all have storage tanks and recycling programs to dispose of used oil.

Question: What type of motor oil is best for my engine?

Answer: The type specified by the vehicle manufacturer in your owner's manual. For most passenger car and light truck gasoline engines today, it's any oil that meets the American Petroleum Institutes "SH" rating.

As for the viscosity of oil to use, most new engines today require a multiviscosity 5W-30 oil for all-round driving. The lighter 5W-30 oils contain friction reducing additives that help improve fuel economy, and also allow the oil to quickly reach critical upper valvetrain components when a cold engine is first started. Most engine wear occurs immediately after a cold start, so it's important to have oil that is thin enough to circulate easily -- especially at cold temperatures.

For older engines and ones that are driven at sustained highways speeds during hot weather, 10W-30 or 10W-40 is a good choice. Heavier multiviscosity oils such as 20W-40 are for high rpm, high-load applications primarily and are not recommended for cold weather driving.

Straight weight 30W and 40W oils aren't very popular anymore, but some diehards insist on using them. They say the thicker oil holds up better under high temperature (which it does), increases oil pressure and reduces oil consumption in high mileage engines. But straight 30W and 40W oils are too thick for cold weather and may make an engine hard to start. They may also be too thick to provide adequate start-up lubrication to critical upper valvetrain components during cold weather. So switching to a straight 20W oil would be necessary for cold weather driving. Straight 10W oil can also improve cold starting, but is very thin and should only be used in sub-zero climates. A multiviscosity 10W-30 or 10W-40 will provide the same cold starting benefits of a 10W oil and the high temperature protection of a 30W or 40W oil.

SYNTHETIC OILS

For the ultimate in high temperature protection, durability and all-round performance, synthetic oils are the way to go. Unfortunately, most synthetic oils cost up to three times as much as ordinary petroleum-based oils. They cost more because synthetics are manmade rather than refined from petroleum. But this improves their performance in virtually every aspect:

Superior temperature resistance. Synthetics can safely handle higher operating temperatures without oxidizing (burning) or breaking down. The upper limit for most mineral based oils is about 250 to 300 degrees F. Synthetics can take up to 450 degrees F. or higher. This makes synthetics well-suited for turbo applications as well as high rpm and high output engine applications.
Better low temperature performance. Synthetics flow freely at subzero temperatures, pouring easily at -40 or -50 degrees F. where ordinary oils turn to molasses. This makes for easier cold starts and provides faster upper valvetrain lubrication during the first critical moments when most engine wear occurs.
Better engine performance. Synthetics tend to be more slippery than their petroleum-based counterparts, which improves fuel economy, cuts frictional horsepower losses and helps the engine run cooler. The difference isn't great, but it can make a noticeable difference.
Longer oil change intervals. Because synthetics resist oxidation and viscosity breakdown better than ordinary motor oils, some suppliers say oil change intervals can be safely extended -- in some cases stretched to as much as 25,000 miles. Such claims are justified by the fact that synthetics don't break down or sludge up as fast as ordinary mineral-based oils do in use.

CAUTION: For vehicles under warranty, extending the normal change interval is not recommended because failing to follow the OEM's maintenance schedule can void your warranty.

Synthetics are available in the same grades as ordinary motor oils (5W-30, 5W-20 and 10W-30) as well as "extended" grades such as 15W-50 and even 5W-50.

There are also lower-cost synthetic "blends" that combine synthetic and petroleum-based oils in the same container. But you can do your own blend to save money by simply substituting a quart or two of synthetic oil for conventional oil when you change oil. Synthetics are compatible with conventional motor oils.

Who should use a synthetic oil? The premium-priced oil is best for:

Turbocharged or supercharged engines
Performance or high output engines
Vehicles used for towing (especially during hot weather)
Vehicles that are operated in extremely cold or hot climates
Anyone who wants the ultimate in lubrication and protection

Question: My engine uses oil. I'm always adding oil so why should I ever change it?

Answer: You should still change your oil and filter periodically to get rid of contaminants and sludge that build up in the crankcase. Just because your engine uses oil doesn't mean the oil that's in it stays clean. It doesn't. It gunks up just as fast as the oil in an engine that doesn't burn oil. In fact, it probably gunks up faster because of increased blow by due to the worn pistons and rings.

If you never change the oil, sooner or later the filter will plug up. And once that happens, you've lost all protection against dirt and abrasives. Before long, the bearings will become worn and you'll hear the rods knocking. Keep driving and something will eventually let go. End of engine. End of story.

Under hood Maintenance: Drive Belts

2008-01-30T13:49:00.000-08:00

Inspect and Adjust Engine Accessory Drive Belts

Many engine accessories--including the alternator, fan, and coolant pump--are operated by drive belts. If these belts break or slip, the components they drive will fail to work. The belt that drives the fan also drives the coolant pump. If it breaks, coolant and air circulation stop, and the engine overheats at once.

Drive belts should be inspected for a potential problem anytime you have the hood of a customer's car up. A quick inspection can locate a problem and save your customer a major problem.

CAUTION: Never try to adjust or inspect belts with the engine running. Make sure no one is in the car who could start the engine during belt inspection.

To inspect the belts, grab the belt in your hand and twist it so you can see the underside of the "V" shape on V-type belts, or the ribs on a serpentine-type belt. Use a trouble or flashlight so you can make a close inspection. Cracks indicate the belt is getting ready to fail. Oil-soaked belts can slip and not rotate the component they are driving fast enough. Glazed belts have a shiny appearance; this occurs when a belt is not tight enough and the slipping polishes its surface. Torn or split belts have major damage and must be replaced immediately.

Before adjusting any drive belt, always check the service manual for specific instructions. Find the longest span in the belt and push on it as shown below. It should move in about half an inch per foot of free span. If it moves more than this, the belt is too loose. If it moves less, it is too tight.

A belt tension gauge can also be used for testing belt tension. These gauges are operated differently, so follow the instructions on the tool. Basically, you attach the gauge to the longest span of the belt. Then you pull on the belt and measure the tension. Specifications are available in the shop service manual to compare against your reading.

Most belts are adjusted by loosening the support for the alternator and moving it back and forth to tighten or loosen the belt. Other systems use an idler pulley for the adjustment. First loosen the adjustment fastener on the slotted alternator support. Wedge a prybar between a strong part of the engine and the alternator. Pull on the pry bar to move the alternator housing in a direction to tighten the belt. Tighten the adjustment fastener. Recheck the adjustment by measuring the belt as explained earlier.

Remove and Replace an Accessory Drive Belt

When you have determined that a drive belt is defective and needs to be replaced, you should have the replacement belt on hand. Loosen the adjustment fastener on the alternator or idler pulley. Push the alternator or idler pulley inward to loosen the belt. Pull the old drive belt off the pulleys.

Place the new and old belt side by side on the work bench to make a comparison. The belt width and length of the new belt must be the same. If you find a difference, check to see that you have not gotten the wrong belt. A belt that is too long to be adjusted properly will slip. A belt that is too short will not fit over the pulleys. A belt with the incorrect width or V shape could be thrown off when the engine is running.

Install the correct belt over the pulleys. Adjust the belt to the proper tension as described previously. Start the engine and observe the belt in operation. Stop the engine and recheck the tension.

SERVICE TIP: There is an old trick tow truck drivers use when responding to cars that are disabled because of a broken drive belt. They carry packages of women's pantyhose. They wind them around the pulleys and then tie them in a knot. The pantyhose will work as a belt for a short distance to get the car to a service facility.

Question:

How do I know if a V-belt needs to be replaced?
Answer:

One way to find out is to examine the belt. If a V-belt is full of tiny cracks, frayed, has pieces of rubber missing, is peeling or otherwise damaged, it needs to be replaced -- NOW. Also, if a belt is oil soaked or "glazed" (hard shiny appearance on the sides of the belt) it also needs to be replaced. Either of these two conditions can cause the belt to run hot, which can weaken it and increase the danger of it breaking.
Unfortunately, a visual inspection alone isn't a sure-fire method of determining the true condition of a belt because internal wear that you can't see is just as important as external wear that you can see. All belts are reinforced with cords. The cords are what give the belt its strength and keep it from stretching or breaking. But as a belt ages, the constant flexing, heat and strain weakens the cords. Eventually the cords reach a point where failure can happen suddenly and unexpectedly. The belt may still look good as new on the outside, but be on the verge of snapping internally because the cords have lost their strength.

So the other factors that need to be considered when judging the condition of a V-belt include the belt's mileage and age. A V-belt that's more than three or four years old and has more than 40,000 or 50,000 miles on it may be a belt that is nearing the end of its useful service life. For this reason, you might be well advised to replace a high mileage belt even if it still looks okay.

Question:

Is it necessary to replace belts periodically?
Answer:

Yes. Although the auto makers don't usually specify a replacement interval for V-belts or serpentine (flat, multi-ribbed) belts, most belt manufacturers do recommend periodic replacement for preventative maintenance. Here's why: the incidence of belt failure rises sharply in the fourth year of service for the typical V-belt, and the fifth year for serpentine belts.
What's more, eight out of ten V-belt failures and ten out of ten serpentine belt failures end up causing a breakdown! That's because belts have the uncanny knack of always picking the worst possible moment to fail -- like when you're heading out of town on that long-awaited fishing trip, when you're hurrying to pick up a hot date who told you NOT to be late, or when you're giving your dear mother-in-law a ride to church.

A broken belt is always bad news because when it snaps, all drive power to whatever it turns is lost. That means the water pump quits circulating coolant through the engine, the alternator quits producing amps, the power steering pump ceases to assist steering, and the air conditioner quits cooling. Many newer vehicles have a single serpentine belt that drives all of the engine's accessories, so when it fails everything stops working.

The good news is that replacing the belts periodically can go a long way towards minimizing the risk of a breakdown caused by belt failure. After all, it's a lot easier to replace a belt at your convenience than having the belt fail unexpectedly Heavens knows where.

For optimum protection, most experts recommend replacing V-belts every three to four years, or every 36,000 to 48,000 miles. A recommended replacement interval for serpentine belts would be every four or five years, or 50,000 miles.

BELT LIFE

The service life of a V-belt depends on mileage as well as load, tension and heat. Every time a belt passes around a pulley, it bends and flexes. This produces heat which age hardens the rubber over time. The wear process can be greatly accelerated if the belt is loose and slips because any added friction between belt and pulley makes the belt run even hotter. This can cause glazing on the faces of the belt and cause it to slip even more. So one of the most important factors that affects belt life is making sure it is properly tensioned when it is installed and that the proper tension is maintained throughout its service life.

Symptoms that may be the result of improper belt tension include:

Belt squeal, especially on the fan, A/C compressor or power steering drives.
A battery that keeps running down (due to belt slippage).
Excessive sidewall wear on a V-belt that causes it to ride lower than normal in the pulley grooves.
Severe cracking along the underside of a V-belt.
Noisy alternator, power steering pump, air pump, A/C compressor or water pump bearings (from excessive belt tension).

BELT REPLACEMENT

Replacement V-belts must be the same length and width as the original. A belt that's too long or too short may not allow enough adjustment for proper tension. A belt that's too wide or too narrow will not ride at the right depth in the pulley grooves.

CAUTION: When installing a new belt, do not attempt to "stretch" it over pulleys. Doing so can break the internal cords causing the belt to fail. Always loosen the pulleys so there is adequate clearance to slip the belt over the pulleys.

Once the belt has been installed on the pulleys, a belt gauge should be used to adjust belt tension to factory specifications. The old rule of thumb of allowing 1/2 inch of "give" between the furthest pulleys is not a very accurate guide for today's engines. So follow the manufacturer's recommendations for belt tension.

Once tension has been adjusted, it should be rechecked and readjusted (if necessary) after a short break-in period (say after 500 to 1,000 miles of driving). It should then be checked twice a year or every 5,000 or 6,000 miles thereafter.

On vehicles with a single serpentine belt, tension is usually self-adjusted automatically via a spring loaded tensioner. No additional adjustment is necessary.

If your engine has been eating or twisting belts, misaligned pulleys may be your problem. Alignment can be checked with a straightedge. If a pulley is bent or not in the same plane as the rest, the problem should be corrected otherwise the "bad" pulley will continue to ruin belts.

Under hood Maintenance: Coolant

2008-01-30T13:46:00.000-08:00

Question: How often should I change my antifreeze?

Answer: For "ordinary" antifreeze, the vehicle manufacturers generally recommend coolant changes every two to three years or 30,000 miles. Others say it's not a bad idea to change the coolant every year for maximum corrosion protection -- especially in vehicles that have aluminum heads, blocks or radiators. But such recommendations may soon be obsolete. Several antifreeze suppliers have just recently introduced "long life" antifreeze formulations that claim to provide protection for four years or 50,000 miles.

General Motors just introduced a new five year, 100,000 mile antifreeze in its 1996 cars and light trucks. The new coolant is called "Dex-Cool" and is dyed orange to distinguish it from ordinary antifreeze (which is green).

CAUTION: These new long life coolants provide extended life only when used in a clean system mixed with water. If mixed with ordinary antifreeze and/or old coolant in a system, the corrosion protection is reduced to that of normal antifreeze (2 to 3 years and 30,000 miles).

CORROSION INHIBITORS

The life of the antifreeze depends on it's ability to inhibit corrosion. Silicates, phosphates and/or borates are used as corrosion inhibitors to keep the solution alkaline. As long as the antifreeze remains so, corrosion is held in check and there's no need to change the coolant. But as the corrosion inhibiting chemicals are used up over time, electrolytic corrosion starts to eat away at the metal inside the engine and radiator. Aluminum is especially vulnerable to corrosion and can turn to Swiss cheese rather quickly when conditions are right. Solder bloom can also form in copper\brass radiators causing leaks and restrictions. So changing the coolant periodically as preventative maintenance is a good way to prevent costly repairs.

The basic idea is to change the coolant before the corrosion inhibitors reach dangerously low levels. Following the OEM change recommendations is usually good enough to keep corrosion in check, but it may not always be the case. That's why more frequent changes may be recommended to minimize the risk of corrosion in bimetal engines and aluminum radiators.

CHECKING THE ANTIFREEZE

One way to find out if it's time to change the antifreeze is to test it. Several suppliers make special antifreeze test strips that react to the pH (alkalinity) of the coolant and change color. If the test strip indicates a marginal or bad condition, the coolant should be changed.

CHANGING THE COOLANT

Reverse flushing is the best way to change the coolant because draining alone can leave as much as 30 to 50% of the old coolant in the engine block. Reverse flushing also helps dislodge deposits and scale which can interfere with good heat transfer.

The concentration of antifreeze in the coolant also needs to be checked prior to the onset of cold weather. A 50/50 mixture of antifreeze and water is recommended and will protect against freezing down to -34 degrees F and boilover protection to 263 degrees F.

For maximum protection, up to a 70% mixture of antifreeze can be used for freezing protection to -84 degrees F.

CAUTION: Do not use more than 70% antifreeze, and never run straight water in the cooling system because it offers no corrosion, freezing or boilover protection.

Question:

I've heard about a new "environmentally safe" nonpoisonous antifreeze. What is it?
Answer:

It's propylene glycol (PG) antifreeze, sold under the "Sierra" brand name. Every other brand of antifreeze contains ethylene glycol (EG).
Antifreeze made with propylene glycol is being marketed as a "safer" alternative to ordinary antifreeze. Though it is by no means safe to drink, it is significantly less toxic than ordinary ethylene glycol antifreeze -- which may be a important difference to pet owners and parents of small children. PG also has an unpleasant taste which discourages further sampling by thirsty animals and toddlers. Safety is an important issue with coolants because of the frequency of spills, leaks and improper disposal.

According to one supplier of PG-based antifreeze, over 3,000 people in the U.S. were treated for ingesting antifreeze in 1991 (the latest year for which figures were available). Eight of them died. Had the antifreeze they ingested contained PG instead of EG, the consequences may not have been so dire.

Because of its significant safety advantages, PG coolants represent far less risk to wildlife in case of spills, leaks, or careless disposal. Because of this it can be claimed that PG coolants have an environmental benefit. However, both PG and EG are biodegradable and both may pick up lead or other heavy metals once they've been used in a cooling system. Both types of coolants, after being used, should be disposed of properly and in compliance with local regulations.

Though some auto makers were initially cautious about using PG when it was first introduced, GM has now said that propylene glycol may be used in GM vehicles without voiding the manufacturer's warranty coverage and will perform adequately under most vehicle operating conditions. Most vehicle manufacturers, however, don't currently use PG as a factory-fill antifreeze because of its higher cost (about $1 more per gallon at retail).

PERFORMANCE COMPARISON

When mixed with water (50/50 ratio), ordinary ethylene glycol antifreeze provides freezing protection to -34 degrees F. and boilover protection to 263 degrees F.. By comparison, propylene glycol provides freezing protection down to -27 degrees F. in a 50/50 mixture and boilover protection to 257 degrees F.. Though it might be argued that PG provides a few degrees less protection than EG, the difference can be easily offset by using a slightly higher concentration of PG in the coolant mix.

In terms of thermal efficiency (heat transfer), both types of antifreezes perform about the same (though EG has a marginal edge). Corrosion protection is about the same as long as the coolant is properly formulated with inhibitors.

ANTIFREEZE DISPOSAL & RECYCLING

Regardless of the type of antifreeze you use, it should be disposed of properly. In many areas, it is okay to flush used coolant down the toilet (sanitary sewer) as long as the amount does not exceed a few gallons. But it should not be poured down a floor drain or into a storm sewer.

Both types of antifreeze are biodegradable but take some time to break down. Dumping used antifreeze into a storm sewer, ditch, creek or on the ground can contaminate ground water and kill plants and fish. What's more, used antifreeze picks up lead from solder in copper/brass radiators. Lead is a toxic heavy metal that can also cause pollution problems of its own.

Some areas prohibit ANY dumping of used coolant (sanitary or storm sewers). They also may not accept used antifreeze in a sealed container for landfill collection because eventually the container will leak its contents into the ground causing possible ground water contamination.

So how do you get rid of the stuff? You can take it to a local collection center that accepts used antifreeze for disposal or recycling, you can pay to have it disposed of as a hazardous waste (yeah, right) -- or you can take your vehicle to a garage or service facility that has a coolant recycling machine. The latter is the best choice because it eliminates the disposal problem altogether.

Coolant recycling machines work their magic by a variety of means. Some use filtration while others use a distillation process to remove the harmful contaminants from the old antifreeze. Corrosion inhibiting chemicals are then added to restore the coolant's corrosion protection. The auto makers have all approved coolant recycling as an effective means of eliminating coolant disposal problems, and each publishes a list of machines that meet their specifications. Recycled coolant must meet minimum standards of purity before it can be reused.

Question:

What are the most common causes of engine overheating?
Answer:

THERMOSTAT STUCK SHUT
The thermostat, which is usually located in a housing where the upper radiator hose connects to the engine, controls the operating temperature of the engine. It does this by blocking the flow of coolant from the engine to the radiator until the engine reaches a certain temperature (usually 190 to 195 degrees F.). When this temperature is reached, the thermostat opens and allows coolant to circulate from the engine to the radiator.

If the thermostat fails to open, which can happen due to mechanical failure or if a steam pocket forms under the thermostat due to incomplete filling of the cooling system or coolant loss, no coolant will circulate between the engine and radiator, and the engine will quickly overheat.

You can check for this condition by carefully touching the upper radiator hose when the engine is first started and is warming up. If the upper radiator hose does not become hot to the touch within several minutes after starting the engine, it means the thermostat is probably defective and needs to be replaced.

CAUTION: The replacement thermostat should always have the same temperature rating as the original. Do not substitute a colder or hotter thermostat on any vehicle that has computerized engine controls as engine operating temperature affects the operation of the fuel, ignition and emissions control systems.

DEFECTIVE FAN CLUTCH

On rear wheel drive vehicles with belt-driven cooling fan, a "fan clutch" is often used to improve fuel economy. The clutch is a viscous-coupling filled with silicone oil. The clutch allows the fan to slip at high speed, which reduces the parasitic horsepower drag on the engine. If the clutch slips too much, however, the fan may not turn fast enough to keep the engine cool.

The silicone fluid inside the clutch breaks down over time and can leak out due to wear, too. If you see oily streaks radiating outward on the clutch (and/or the fan can be spun by hand with little or no resistance when the engine is off), it means the clutch is bad and needs to be replaced. Any play or wobble in the fan due to wear in the clutch also signals the need for a new clutch.

INOPERATIVE FAN MOTOR

On most front-wheel drive cars, the fan that cools the radiator is driven by an electric motor. A temperature switch or coolant sensor on the engine cycles the fan on and off as additional cooling is needed. If the temperature switch or coolant sensor (or the relay that routes power to the fan motor is bad), the fan won't come on when it is needed and the engine will overheat. Likewise, if the fan motor itself is bad, the fan won't work.

The system needs to be diagnosed to determine where the problem is so the correct component can be replaced.

EXTERNAL COOLANT LEAKS

Leaks in radiator or heater hoses, the water pump, radiator, heater core or engine freeze plugs can allow coolant to escape. No engine can tolerate the loss of coolant for very long, so it usually overheats as soon as a leak develops.

A visual inspection of the cooling system and engine will usually reveal where the coolant is going.

Leaks in hoses can only be fixed by replacing the hose. Leaks in the water pump also require replacing the pump. But leaks in a radiator, heater hose or freeze plug may sometimes respond to a sealer added to the cooling system.

WEAK OR LEAKY RADIATOR CAP

If no leaks are apparent, the radiator cap should be pressure tested to make sure it is holding the specified pressure. If the spring inside the cap is weak (or the cap is the wrong one for the application), the engine will lose coolant out the overflow tube every time it gets hot.

INTERNAL COOLANT LEAK

If there are no visible coolant leaks, but the engine is using coolant, there may be a crack in the cylinder head or block, or a leaky head gasket that is allowing coolant to escape into the combustion chamber or crankcase.

See related question #16 for more information.

EXHAUST RESTRICTION

In some instances a severe exhaust restriction can produce enough backpressure to cause an engine to overheat. The most likely cause of the blockage would be a plugged catalytic converter or a crushed or damaged pipe. Checking intake vacuum and/or exhaust backpressure can diagnose this kind of problem.

BAD WATER PUMP

In a high mileage engine, the impeller that pumps the coolant through the engine inside the water pump may be so badly corroded that the blades are loose or eaten away. If such is the case, the pump must be replaced.

Most pump failures, however, occur at the pump shaft bearing and seal. After tens of thousands of miles of operation, the bearing and seal wear out. Coolant starts to leak out past the shaft seal, which may cause the engine to overheat due to the loss of coolant. A sealer additive will not stop this kind of leak. Replacing the water pump is the only cure.

CAUTION: A leaky water pump should be replaced without delay, not only to reduce the risk of engine overheating but to prevent catastrophic pump failure. If the shaft breaks on a rear-wheel drive vehicle, the fan may go forward and chew into the radiator ruining the radiator.

Question:

Will a radiator stop leak additive really stop a coolant leak?
Answer:

Yes, but only if the leak is in a component that normally responds to such a product.
Leaks that can often be sealed with an additive include radiator and heater core pinholes (but not cracks), seepage leaks around engine freeze plugs, thermostat, manifold and head gaskets, and porosity leaks in aluminum heads or blocks.

Leaks that do not usually respond to additives include leaks in hoses, the water pump (around the shaft), or the radiator cap. Large cracks, cracks along outside corners or where hoses attach to the end tanks on the radiator are also very difficult to seal.

Even if a leak is sealed by an additive, no manufacturer will guarantee that such a seal will last. Repairing or replacing the leaky component, therefore, is the best cure -- and the only one that will guarantee lasting results.

Question:

My cooling system keeps losing coolant, but I don't see any leaks. Where is it going?
Answer:

You probably have an "internal" coolant leak inside your engine. The coolant is escaping into the combustion chamber or crankcase through cracks in the cylinder head or block, or through a leaky head gasket.
In rare instances, coolant may also leak into the automatic transmission fluid cooler if one is located inside the radiator. But usually when automatic transmission fluid leaks into the coolant it means the line is leaking.

Pressure testing the cooling system is necessary to diagnose an internal leak. A "cylinder leak-down test" can tell a mechanic if the coolant leak is in the combustion chamber. But to pinpoint an internal leak, it is usually necessary to remove the head(s) from the engine. The head may then be pressure tested and/or checked for cracks using special equipment.

Minor internal leaks can sometimes be temporarily sealed by adding a sealer to the cooling system. But large leaks or ones that do not respond to a sealer will have to be fixed.

If the problem is a cracked head or block, repairs may or may not be possible depending on the nature of the crack. Cracks in aluminum can often be repaired by welding while those in cast iron can be fixed by pinning the damaged area. But some cracks may be so bad that they are beyond repair or in a location that makes repair impossible. In such cases, the head or block must be replaced.

If a leaky head gasket is the culprit, replacing the gasket may only temporarily cure the problem if the head or block is warped. The mating surfaces on both the head and block should be checked for flatness and resurfaced if necessary to restore flatness for a proper seal.

Under hood Maintenance: Brake Fluid

2008-01-30T13:45:00.000-08:00

Question: My brake pedal slowly sinks to the floor when I hold my foot on it. What's wrong?

Answer: You either have a fluid leak in your brake system or your master cylinder is defective. Either way, your brakes need immediate attention.

If the brake warning light is on, you most likely have a fluid leak. Your vehicle may not be safe to drive in this condition! You should have the brakes inspected as soon as possible to determine where the fluid is leaking (usually a hose, brake line, brake caliper or wheel cylinder) so the necessary repairs can be made.

If the brake warning light is not on, it does not necessarily mean you do not have a leak. The warning light only comes on when there's been enough fluid loss to create a pressure differential between the two sides of the hydraulic system that actually apply the brakes.

The brake system is divided into two hydraulic circuits. On most rear-wheel drive vehicles, it is divided so one circuit applies the front brakes and the other applies the rear brakes. On front-wheel drive cars and minivans, the system is usually split diagonally. One circuit works the right front and left rear brake, and the other works the left front and right rear brake. This is done for safety purposes so if one circuit loses all its brake fluid and fails, the vehicle will still have one remaining circuit to apply two wheel brakes.

A quick way to check for leaks in either circuit is to simply check the fluid level in the master cylinder reservoir. The reservoir is divided into two chambers (one for each brake circuit). If one chamber is unusually low or empty, there's a leak somewhere in that circuit. The brakes should then be inspected to check for fluid leaks. Wet spots around hose or line connections, or fluid leaking from a disc brake caliper or drum wheel cylinder would indicate a serious problem that needs immediate attention.

If the brake warning light is not on and there are no apparent leaks, then the master cylinder may be worn or leaking internally allowing the pedal to slowly sink when pressure is applied to it. This type of condition will be most noticeable when holding constant pressure against the brake pedal at a stop light. If the pedal sinks or requires pumping to keep the car from creeping ahead, the master cylinder needs to be replaced.

On some vehicles with rear-wheel antilock brake systems (ABS), it's also possible that a leak in the ABS unit may cause a similar sinking pedal condition.

Question:

My brake pedal is low when I step on it, but it comes up when I pump the brakes. Do I need new brakes?
Answer:

A low brake pedal that has to be pumped repeatedly to bring a vehicle to a stop may be due to a low fluid level, drum brakes that need adjustment or air in the lines. It usually has nothing to do with the condition of the brakes and certainly isn't grounds for a brake job.
If the pedal feels "soft" or "spongy" instead of firm, there's probably air in the system. This will require "bleeding the brakes" to remove air from the lines, calipers and wheel cylinders.

The first thing that should be checked is the fluid level in the master cylinder reservoir. If the level is low, there's a leak somewhere in the hydraulic system that must be found and repaired. Adding fluid will only cure the symptom, not the cause, and sooner or later the level will be low again creating a dangerous situation. So check for leaks around the master cylinder, wheel cylinders, brake calipers, rubber brake hoses and steel brake lines.

If the fluid level is okay, the adjustment of the rear brakes should be checked next (assuming the vehicle has drum brakes in the rear -- if it has drums all the way around, check the front drums first, then the rear). The shoes should be close enough to the drums to produce just a hint of drag when the wheels are rotated by hand. An excess of slack probably means the self-adjusters are either frozen or fully extended.

If adjusting the drum brakes fails to eliminate the low pedal, the wheel and drum will have to be removed so the adjusters can be freed up or replaced, and/or so the worn brake shoes can be replaced.

If the vehicle has rear disc brakes, the adjusting mechanism in the rear caliper pistons that maintain the correct pad-to-rotor clearance may be corroded, frozen or worn out. In most cases, the piston assemblies cannot be rebuilt and must be replaced.

If the fluid reservoir is full and the brakes are properly adjusted, but the pedal is low (or feels spongy), there is probably air in the brake lines. Air is compressible, so every time you step on the pedal, the bubbles collapse instead of transferring pressure to the brakes. The cure here is to bleed the brake lines following the factory recommended sequence.

Brakes are usually bled in a specified sequence (always refer to a shop manual for the exact procedure for your vehicle). Usually the rear brakes are bled first, then the ones up front on most rear-wheel drive cars and trucks. But on front-wheel drive cars and minivans, the hydraulic system is split diagonally so the brakes are bled in opposite pairs (right rear and left front, then left rear and right front). Following the proper sequence is important so air doesn't remain trapped in the lines.

On late model GM and Ford cars with quick take-up master cylinders, the quick take-up valve takes about 15 seconds to reseat after the brake pedal has been depressed. If the pedal is pumped too quickly while manually bleeding the system, you may never get the pedal to firm up. Most professionals use pressure bleeding equipment to bleed the brakes because it is faster and easier.

Under hood Maintenance: Battery

2008-01-30T13:40:00.000-08:00

Q & A: Battery

1. How can I tell if my battery is low and needs to recharged?
Answer:

The first and most likely indication of a low battery would be a hard starting problem caused by slow cranking. If the battery seems weak or fails to crank your engine normally, it may be low. To find out, you need to check the battery's "state of charge."
A battery is nothing more than a chemical storage device for holding electrons until they're needed to crank the engine or run the lights or other electrical accessories on your vehicle. Checking the battery's state of charge will tell you how much juice the battery has available for such purposes.

If your battery is low, it needs to be recharged, not only to restore full power, but also to prevent possible damage to the battery. Ordinary automotive lead-acid storage batteries must be kept at or near full charge to keep the cell plates from becoming "sulfated" (a condition that occurs if the battery is run down and left in a discharged condition for more than a few days). As sulfate builds up, it reduces the battery's ability to hold a charge and supply voltage. Eventually the battery becomes useless and must be replaced.

CHECKING THE STATE OF CHARGE

The charge level depends on the concentration of acid inside the battery. The stronger the concentration of acid in the water, the higher the specific gravity of the solution, and the higher the state of charge.

On batteries with removable caps, state of charge can be checked with a "hydrometer." Some hydrometers have a calibrated float to measure the specific gravity of the acid solution while others simply have a number of colored balls. On the kind with a calibrated float, a hydrometer reading of 1.265 (corrected for temperature) indicates a fully charged battery, 1.230 indicates a 75% charge, 1.200 indicates a 50% charge, 1.170 indicates a 25% charge, and 1.140 or less indicates a discharged battery. On the kind that use floating balls, the number of balls that float tells you the approximate level of charge. All balls floating would indicate a fully charged battery, no balls floating would indicate a dead or fully discharged battery.

Some sealed-top batteries have a built-in hydrometer to indicate charge. The charge indicator only reads one cell, but usually shows the average charge for all battery cells. A green dot means the battery is 75% or more charged and is okay for use or further testing. No dot (a dark indicator) means the battery is low and should be recharged before it is returned to service or tested further. A clear or yellow indicator means the level of electrolyte inside has dropped too low, and the battery should be replaced.

On sealed-top batteries that do not have a built-in charge indicator, the state of charge can be determined by checking the battery's base or open circuit voltage with a digital voltmeter or multimeter. This is done by touching the meter leads to the positive and negative battery terminals while the ignition key is off.

A reading of 12.66 volts indicates a fully charged battery; 12.45 volts is 75% charged, 12.24 volts is 50% charged, and 12.06 volts is 25% charged.

RECHARGING THE BATTERY

CAUTION: Do not attempt to recharge a battery with low (or frozen) electrolyte! Doing so risks blowing up the battery if the hydrogen gas inside is ignited by a spark.

Your charging system should be capable of recharging the battery if it is not fully discharged. Thirty minutes or so of normal driving should be enough.

If your battery is completely dead or extremely low, it should be recharged with a fast or slow charger. This will reduce the risk of overtaxing and damaging your vehicle's charging system. One or both battery cables should be disconnected from the battery prior to charging it with a charger. This will eliminate any risk of damage to your vehicle's electrical system or its onboard electronics.

Question:

2. My battery keeps running down. Do I need a new battery?

Answer:

It might, but then again it might not. The only way to know for sure is to (1) test the condition of the battery to see if it is capable of holding a charge, (2) check the output of the charging system to see if it is functioning properly, and (3) if the battery and charging system are okay, check for a possible current drain on the battery when the key is off. In other words, if the battery is okay and the charging system is doing its job, then something is draining voltage from the battery and running it down when the key is off.
One way to check the battery is to recharge it, then let it sit for a day with both battery cables disconnected. If the battery holds the charge and doesn't run down, it's probably okay, and the problem is in your charging system or wiring.

To see if the charging system is working properly, start the car and turn on the headlights. If the headlights are dim, it indicates the lights are running off the battery and that little or no juice is being produced by the alternator. If the lights get brighter as you rev the engine, it means the alternator is producing some current, but may not be producing enough at idle to keep the battery properly charged. If the lights have normal brightness and don't change intensity as the engine is revved, your charging system is functioning normally.

You can also check the charging system by connecting the leads of a voltmeter to the battery. When the engine starts, the charging voltage should jump to about 14.5 or higher. If the reading doesn't change or rises less than a volt, you have a charging problem that will require further diagnosis.

If the battery and charging system seem to be working normally, the only thing that's left is the electrical system. If the battery runs down overnight or when the vehicle sits for several days, it means something is remaining on and drawing current when the ignition is turned off. It may be a trunk light or cigarette lighter that remains on all the time, a fuel pump relay or other relay with frozen contacts that's drawing current, a rear window defroster that doesn't shut off, or a short in the radio or other electrical accessory.

All vehicles draw a little current from the battery when the key is off to run the clock, keep the memory alive in a digital radio (so it doesn't forget the station settings) and the engine computer. Alarm systems need current to keep their circuits armed as do cellular phones.

Current drain on the battery can be checked with an ammeter. Make sure the ignition is off, then disconnect one of the battery cables. Connect one ammeter lead to the battery and the other to the cable. The normal current drain on most vehicles should be about 25 milliamps or less. If the key-off drain exceeds 100 milliamps, there's an electrical problem that requires further diagnosis.

Finding the hidden current drain can be time consuming. The easiest way to isolate the problem is to pull one fuse at a time from the fuse panel until the ammeter reading drops. This will tell you which circuit is draining the battery. Then you have to check the wiring and each of the components in that circuit to pinpoint the problem.

Question:

3. How can I tell if my battery is good or bad?

Answer:

The condition of the cell plates inside the battery determines whether or not a battery is still serviceable. Current is produced when sulfuric acid in the battery reacts with lead in the cell plates. As the battery discharges, sulfate accumulates on the plates and reduces the battery's ability to make current. The sulfate is returned to solution when the alternator recharges the battery by forcing current to flow in the opposite direction.
Over time, some of the sulfate becomes permanently attached to the plates. The sulfate forms a barrier that diminishes the battery's ability to produce and store electricity. This process can be accelerated if the battery is run down frequently or is allowed to remain in a discharged state for more than a few days. If the plates have become sulfated, therefore, the battery won't accept a charge and will have to be replaced.

Average battery life is only about four to five years under the best of circumstances -- and sometimes as short as two to three years in extremely hot climates such as Arizona and New Mexico. But the battery may become "sulfated" prematurely if it is chronically undercharged (charging problems or frequent short-trip driving), or if the water level inside the battery drops below the top of the cell plates as a result of hot weather or overcharging and allows the cell plates to dry out.

BATTERY TESTING

This is something you can't really do yourself, so you need to take your vehicle to a service facility that has the proper test equipment. The battery's condition can be determined one of two ways: with a carbon pile "load test" (that applies a calibrated load to the battery) or electronically with a special tester that measures the battery's internal resistance.

Equipment that uses a carbon pile for load testing requires the battery to be at least 75% charged. If the battery is less than 75% charged, a good battery may fail the test. So the state of charge must be checked first, and the battery recharged if it is low prior to testing. NOTE: The battery does NOT have to be fully charged prior to testing if an electronic tester that measures internal resistance is being used.

If load testing with a carbon pile, apply a load that is equal to half the battery's cold cranking amps (CCA) rating. A good battery should be able to supply half its CCA rating for fifteen seconds without dropping below 9.5 volts.

Question:

4. Does a replacement battery need to be the same size as my old one?
Answer:

No. If your old battery has reached the end of the road and needs to be replaced, or if you think you need a battery with a bigger amp capacity for easier cold weather starting or to handle added electrical accessories (such as a killer stereo system, driving lights, etc.), then there's no reason why you have to install a battery that's the same size as your old one.
The word "size" may be a bit confusing here because what we're really talking about is the battery's amp or power rating, not the physical dimensions of its case.

A battery with a bigger case is not necessarily a more powerful battery. Battery manufacturers can cram a lot of amps into a relatively small box by varying the design of the cell plates and grids. So two batteries with identical exterior dimensions may have significantly different power ratings.

Batteries come in many different sizes and configurations (which are referred to as "group" sizes) because the vehicle manufacturers can't get together and standardize anything. So when you're choosing a battery, you have to consider three things: (1) the group size (height, width, length and post configuration), (2) whether your battery has top or side posts, and (3) how many amps will be needed for reliable cold starting and vehicle operation.

GROUP SIZES

Because there are 57 different group sizes, many aftermarket replacement battery suppliers consolidate group sizes to simplify inventory requirements. So some replacement batteries may not fit exactly the same as the original. The battery may be slightly shorter, taller, narrower or wider than the original. But as long as it fits the battery tray and there are no interference problems (too tall a battery may cause the cables to make contact with the hood causing a dangerous and damaging electrical short!), it should work fine.

Some replacement batteries come with both side and top posts to further consolidate applications. Some also have folding handles to make handling and installation easier.

BATTERY RATINGS

Though many replacement batteries are marketed by the number of "months" of warranty coverage provided (36, 48, 60, etc.), what's more important in terms of performance is the battery's power rating which is usually specified in "Cold Cranking Amps" (CCA) rating. The CCA rating tells you how many amps the battery can deliver at 0 degree F. for 30 seconds and still maintain a minimum voltage of 1.2v. per cell.

In the past, the rule of thumb was to always buy a battery with a rating of at least one CCA per cubic inch of engine displacement. But twice that is probably a better recommendation for reliable cold weather starting.

At the very least, you should buy a replacement battery with the same or better CCA rating as your old battery or one that meets the vehicle manufacturer's requirements. For most small four-cylinder engines, this would be a 450 CCA or larger battery, for a six cylinder application, a 550 CCA or larger battery, and for a V8 a 650 CCA or larger battery. Bigger is usually better. Extra battery capacity is recommended if your vehicle has a lot of electrical accessories such as air conditioning, power windows, seats, electric rear defogger, etc.

BATTERY INSTALLATION

Most batteries are "dry charged" at the factory, which means they're activated as soon as acid is poured into the cells. Even so, the battery may require some charging to bring it all the way up to full charge.

Most experts recommend charging the battery before it is installed regardless of whether it is dry charged or not. This will ensure the battery is at full charge and lessen the strain on your charging system.

When the battery is installed, it must be locked down and held securely by a clamp, strap or bracket. This will not only keep the battery from sliding around on its tray (which might allow the positive cable to touch against something and short out the battery or start a fire!), but will also help to minimize vibration that can damage the battery.

The battery cables should also be inspected to make sure they're in good condition, too. If the cables are badly corroded, don't fit the battery posts or terminals tightly, or have been "fixed" by installing temporary clamps on the ends, the cables should be replaced. At the very least, you should clean the cable clamps and battery posts with a post cleaner, sandpaper or a wire brush to ensure good electrical contact. A light coating of grease, petroleum jelly and/or installing chemically treated felt washers under the cable clamps will help prevent corrosion.

Question:

5. Is there any danger to me or my vehicle if I give someone a "jump start?"

Answer:

Yes. The danger to you is a battery explosion. Batteries contain hydrogen gas, which can ignite and explode if a spark occurs anywhere near the battery. Batteries also contain acid which may be splashed on you if the battery explodes.
The danger to your vehicle is if someone reverses the jumper connections or touches the jumper cables together. The voltage surge that results may damage your charging system and/or other electronic components in your vehicle.

To minimize these risks, use the following procedure when jump starting :

Do not smoke. You should also wear eye protection.
Make sure the vehicles are not touching (contact could provide an unwanted electrical path).
Turn your engine off.
Connect the red jumper cable from the positive (+) post or terminal on your "good" battery to the positive post or terminal on the low or dead battery in the other vehicle.
Connect the black jumper cable from the negative (-) post or terminal on your good battery to a solid ground on the other vehicle.
CAUTION: DO NOT make the final jumper connection directly to the low or dead battery itself.

The reason for not doing this is because the final jumper connection usually produces a spark. Making the final connection away from the battery will minimize any danger of an explosion by keeping the spark well away from the battery.

Make sure the ground connection on the vehicle with the low or dead battery provides a good electrical contact. Use an unpainted metal surface like an engine bracket or a frame member.
Make sure the cables do not touch each other and that the cables are clear of the fan and pulleys on both vehicles.
Start the engine in the vehicle with the good battery. Run the engine at fast idle for several minutes before attempting to start the vehicle with the low or dead battery. This will allow the charging system to pump some life into the other battery lessening the drain on the good battery and charging system.
As soon as the vehicle with the dead battery starts, disconnect the battery cables. The vehicle should then be run or driven at least thirty minutes to recharge the low or dead battery. Additional charging time may be required depending on the battery's condition and state of charge.

If the vehicle does not crank or cranks slowly, recheck the jumper connections. If it still doesn't crank, the problem may be something other then the battery (such as a bad starter, solenoid, battery cable connection or internal engine problem).

If the vehicle cranks normally, but refuses to start, it may have an ignition, fuel or mechanical problem.

Do not crank the starter more than thirty seconds at a stretch. Allow the starter to cool for about two minutes before cranking the engine again. Continuous grinding of the starter can cause it to overheat and fail. Continuous cranking can also sap the juice out of your good battery and/or overload and possibly damage your charging system, too!

Under hood Maintenance: Air Filters

2008-01-30T13:37:00.000-08:00

Even during low speed operation, the engine pulls in a tremendous volume of air. This air has a great deal of abrasive particles, which must be prevented from entering the engine. The air cleaner traps the abrasive particles before they can enter the engine. In so doing, however, it clogs itself. If the air filter is not changed regularly, it can become so clogged that it limits air flow into the engine. Manufacturers specify an air filter change interval, and the change is usually a regular part of underhood maintenance.

The air cleaner has two main components. A housing provides a container for the filter element. The housing is a metal container that is typically mounted on top of the engine. Air is routed into the housing through an intake tube assembly. The intake tube assembly on the air cleaner housing shown above is a simple tube. On late-model cars, the intake tube assembly may be very complex and control the temperature of the incoming air for performance and emission control..

The filter is the part inside the housing that cleans the air. The two basic types of filters are the paper and oil-wetted polyurethane. Heavy duty filters sometimes combine both types of filter types. The filter element is made from pleated paper. The pleats provide the maximum surface area for air to pass through. A fine mesh screen is used to support the paper element and protect against the fire hazards of an engine backfire. A top and bottom seal provides an airtight seal for the filter in the housing. Sealing is important because any air that does not go through the filter on the way into the engine could contain dirt.

Polyurethane is a flexible foam-type material. It can be used to filter air entering the engine. It is usually wetted with oil to improve its filtering ability. Filters used in very dirty conditions are often made of polyurethane and paper in combination. Incoming air is routed first through the polyurethane filter, then through the paper filter.

Replacement air filters are available for most vehicles. The filter has a part number printed on the filter box. Application charts are available in auto parts stores that show what number filter fits any particular car. Application charts are often printed on the filter box, too.

Inspect, Remove, and Replace

When inspecting or changing the air filter element, first look up the procedure in the shop service manual. The manual will explain the specific procedure for removing and replacing the element.

Cars with fuel injection typically have an air filter element located in an air induction assembly like the one shown below. The filter element is located in a rectangular box called the air cleaner housing. The element may be removed by unlatching a series of clamps or unscrewing a series of screws.

Cars with carburetors or throttle body fuel injection often have a large round air cleaner assembly mounted on top of the carburetor. The filter is located inside the air cleaner housing. Remove the top of the air cleaner by taking off a single wing nut as shown below.

To inspect or change the air filter element:

First loosen and remove the latches, screws, or wing nut. Remove the cover and then the air filter element.
Carefully inspect the air filter element. You will find dirt and oil on one side of the filter element. This material has been trapped by the filter material. Any dirt and oil buildup on the filter means it should be changed.
Place the new filter element next to the old one on the work bench. Carefully compare the two filter elements. Both must have the same dimensions. The gaskets on the top and the bottom of the filter elements must be exactly the same.
Place the new air filter element in the air filter housing . Make sure the gasket surface is aligned on both the top and bottom.
Replace the cover and tighten the latches, screws, or wing nut until snug.
WARNING: The air filter gasket must fit correctly and seal properly. A leak at the gasket means that air will go directly into the engine around the gasket without going through the filter element. Abrasives can get into the engine and shorten engine life.

SERVICE TIP: A light coat of grease on the air cleaner gasket of an older car can improve the seal between the air cleaner housing and the air filter element.

Question:

How often should I replace my air filter?
Answer:

It's hard to give a specific time or mileage figure because the life of the filter depends on how much crud it ingests. A filter that lasts 20,000 or even 30,000 miles on a vehicle that's driven mostly on expressways may last only a month or two in a rural setting where the vehicle is driven frequently on gravel roads. Changing it annually or every 15,000 miles for preventative maintenance may be a good recommendation for the city driver, but not its country cousin.
Regardless of the mileage or time, a filter should be replaced before it reaches the point where it creates a significant restriction to airflow. But when exactly that point is reached is subject to opinion.

A slightly dirty filter actually cleans more efficiently than a brand new filter. That's because the debris trapped by the filter element helps screen out smaller particles that try to get through. But eventually every filter reaches the point where it causes enough of a pressure drop to restrict airflow. Fuel economy, performance and emissions begin to deteriorate and get progressively worse until the dirty filter is replaced.

Many heavy-duty trucks have a "restriction" meter on the air filter housing that signals when the filter is dirty enough to need replacing. But lacking such a device, the best you can do is guess.

Removing the filter and holding it up to a light will show you how dirty it is. If it's really caked with dirt, it obviously needs to be replaced. Trying to shake or blow the dirt out is a waste of time because too much of it will be embedded in the filter fibers.

NOTE: Many filters that appear to be dirty are in fact still good and do not really need to be replaced. So it's up to you. If you think it's dirty, replace it. If you don't think it's dirty enough to need replacing, then don't.

Repair Guide: Suspension Basics

2008-01-30T13:33:00.000-08:00

Most suspension systems have the same basic parts and operate basically in the same way. They differ, however, in the way the parts are arranged. The vehicle wheel is attached to a steering knuckle. The steering knuckle is attached to the vehicle frame by two control arms, which are mounted so they can pivot up and down. A coil spring is mounted between the lower control arm and the frame.

When the wheel rolls over a bump, the control arms move up and compress the spring. When the wheel rolls into a dip, the control arms move down and the springs expand. The spring force brings the control arms and the wheel back into the normal position as soon as the wheel is on flat pavement. The idea is to allow the wheel to move up and down while the frame, body, and passengers stay smooth and level. There are four basic types of springs used in suspensions: coil, torsion bar, leaf spring, and air spring. The coil spring is the most popular type of spring in both front and rear suspension systems. It is simply a round bar of spring steel that is wound into the shape of a coil. Usually, the top and bottom coils are closer together than the middle coils. The advantages of the coil spring are its compactness, lack of moving parts, and excellent weight supporting characteristics.

The disadvantage of a coil spring is its weakness in supporting side-to-side or lateral movement. When coil springs are used at the drive wheels, heavy traction bars or torque tubes are often required to maintain axle housing alignment.

A number of vehicles use a torsion bar spring. It is a long, solid steel shaft that is anchored at one end to the suspension's control arm and at the other end to the vehicle's frame. Torsion is the twisting action that occurs in the bar when one end is twisted and the other end remains fixed. When a vertical impact on a wheel is transmitted through the control arm to the torsion bar, the bar twists to absorb the impact. The bar's natural resistance to twisting quickly restores it to its original position, returning the wheel to the road.

A torsion bar can store a significantly higher maximum amount of energy than either an equally stressed leaf or coil spring. The torsion offers important weight savings and it is adjustable. In addition, it requires significantly less space than a coil spring.

The leaf spring is made of several layers of spring steel stacked one upon the other. Usually, there is one main leaf that uses spring eyes for locating and fastening the spring to the frame or underbody. Several other progressively shorter leaves are placed on the main leaf, and the assembly or leaf pack is held together in the middle by a center bolt and on the ends by rebound clips. Some spring packs use fiber or plastic pads between leaves to reduce internal leaf friction. Some vehicles use a single leaf instead of a buildup of multiple leaves. One manufacturer is using a leaf spring manufactured from a nonmetal composite. Leaf springs are usually arched so that the ends are higher than the center when viewed from the side.

The leaf spring is usually mounted in three places. A bushing is installed in each of the spring eyes. A bolt through the bushing in the rear spring eye attaches the rear of the spring directly to the vehicle frame. A shackle assembly is attached to the front spring eye and bushing and is then mounted through a shackle bushing to the frame. The shackle assembly allows the leaf spring to pivot up and down. A pair of U-bolts (one shown) and a tie plate are used to clamp the front or rear axle assembly to the leaf spring.

The main advantage of leaf springs is their ability to control vehicle sway and lateral movement. For these reasons, leaf springs are often used on the rear suspension of rear drive vehicles.

Many late-model luxury cars use air springs. The spring is essentially a rubber bag or bladder full of air. A piston is attached to the lower control arm. Movement of the lower control arm causes the piston to move into the air bladder and compress the air in the bladder. Air pressure is used to regulate how easy or hard the bladder can be compressed. The air bladder is usually connected to an air compressor, which regulates the action of the air spring based on road conditions.

All suspension systems use a shock absorber at each wheel. When the coil, torsion bar, leaf spring, or air spring is deflected, it can oscillate (bounce up and down) uncontrollably, possibly causing the tires to lose contact with the road. This could cause the car to bounce up and down without any control. To prevent this from happening, shock absorbers are used, not to absorb shocks, but to control spring rate and dampen spring oscillations.

The shock absorber is a hydraulic device. One end of the shock absorber is attached to a wheel assembly and the other end is attached to the vehicle frame. Shock absorber movement is limited by forcing fluid inside the shock absorber through passages or orifices. This causes the shock absorber to compress or extend at a slow rate.

When the wheel goes over a bump, the shock absorber compresses. When the wheel goes into a dip, the shock absorber extends slowly. This action dampens spring rate and controls spring oscillation.

As we mentioned previously, the suspension system is designed to provide comfortable, safe ride control. For safety, especially in cornering, the suspension system must keep the wheels upright, or nearly upright, under all conditions of driving; a tire can deliver maximum force to the ground only when its tread is flat on the road. Therefore, the tire should be upright when the car is accelerating and cornering, especially the outside wheel that is carrying most of the load; when braking as the front of the car dips and the rear rises; and finally, when it is deflected up or down by road irregularities.

Inspect Suspension Components for Wear

SERVICE TIP: One of the best ways to diagnose a suspension problem is to go for a ride with the owner. Observe what the car is doing. Ask yourself if the problem occurs during braking, steering, or over bumps. Your observations will help you a great deal when you inspect the suspension system.

Anytime you have a car on a hoist to lubricate the suspension components, you should also check the suspension parts for wear. A car with poor steering control, rapid tire wear, noise during stopping and driving over bumps, or poor steering stability may have a suspension, steering, or wheel alignment problem. You should follow a systematic step-by-step procedure to determine the condition of the parts in each of these areas.

To begin your inspection, raise the vehicle on a hoist so you have plenty of room to make an inspection. You can test for loose wheel bearings by grasping the front tire top and bottom and rocking it in and out. Any noticeable looseness is too much. To make sure any looseness detected is in the wheel bearing, check for relative movement between the rotor or brake drum and backing plate. Upper and lower ball joints on most vehicles perform different functions. They are designed differently and require different inspection techniques. The design differs because one pair, called the weight carriers, always supports the front half of the vehicle weight. The other set, called the friction or follower joints, supports no vertical load, but must maintain a firm, quiet connection between the spindle and the control arm. On most American cars with short, long arm suspension, the lower ball joint is the weight carrier. But on many import models with short, long arm suspension, the upper ball joint carries the load.

To apply the proper checking procedure, identify which ball joints are the weight carriers and which are the friction joints. The weight carrier is always mounted on the control arm to which the coil spring or torsion bar is mounted. The friction joint is always mounted on the unloaded control arm. After identifying the ball joints by function, continue the inspection.

Friction ball joints have a heavy coil spring or rubber insert inside that preloads the ball stud and enables the spring to dampen the vibration and road shock of the wheels. Unfortunately, the spring also makes the ball joints difficult to check because the preload keeps the ball joint tight and makes a simple wheel shake test unreliable. The most accurate way to check a friction joint for wear is to disconnect it from the spindle, put two nuts back on the stud to act as a lock, and turn the stud with an inch-pound torque wrench. If you get a reading between 24 and 96 inch-pounds (2-8 newton-meters) for most cars, the ball joint is in satisfactory condition. When the reading is above or below these limits, something is wrong in the socket and the ball joint should be replaced. This checking procedure should be followed when the vehicle has very high mileage, has performed in especially rough service, or appears not to have had proper maintenance.

Weight-carrying ball joints are constantly twisting and turning in response to the steering and up-and-down motion of the front wheels. This wearing motion continues while the two ball joints are loaded with the vehicle weight.

To check a weight-carrying ball joint, first visually check for the general condition of the ball joint and seal. Then check to determine the amount of wear on the inside of the part. Look for broken seals that let contaminants into the part, which shortens the life of the joint. When possible, check the throat area under the seal for cracks or distortion.

The next step is to unload the ball joint and measure the amount of clearance. Lower the car to the ground and position a jack to unload the suspension. For lower weight carriers, place the support under the lower control arm near the wheel.

For upper weight carriers, place the support under the frame crossmember and support the upper control arm in its operating position with a wedge between the body and upper control arm. Check for loose wheel bearings and adjust if necessary. Wheel bearings must be snug to avoid adding their clearance to that of the ball joints.

The most accurate way to measure internal wear is by using a dial indicator that can measure vertical movement right at the ball joint socket. This eliminates the chance of adding other clearances, such as those created by loose wheel bearings, to the ball joint check measurement. The dial indicator is mounted on the lower control arm, near the ball joint to be checked, with locking pliers or a clamp. The dial indicator plunger is then placed against the ball joint steering knuckle (depending on the type of car being checked) so it can read the vertical movement of the parts when the ball joint is unloaded and the wheel is moved through its full vertical range with a pry bar.

Lock the indicator in place by tightening the flexible coupling. Set the dial indicator to zero. Place the pry bar between the tire and ground and pry up on the bottom of the tire. Then, when the wheel is moved vertically through its full range, the reading shown on the dial indicator will equal the amount of internal ball joint clearance. Compare your readings to specifications in the shop service manual to determine if the ball joint should be replaced.

The lower ball joint is the only ball joint on MacPherson strut units. To check it, grasp the lower arm near the ball joint and force the arm up and down to check for looseness, or push and pull on the tire near the ball joint. If there is any movement, the ball joint should be replaced.

Many vehicles use ball joints with built-in wear indicators. Wear indicator-type ball joints must remain loaded to check for wear. The vehicle should be checked with the suspension at curb height. The most common type of wear indicator has a small diameter boss that protrudes from the center of the lower housing. As wear occurs internally, this boss will gradually recede into the housing. When it is flush with the housing, the ball joint should be replaced.

You are ready now to visually check each of the control arm bushing assemblies. Control arm cross shafts and bushings provide the inner hinges for the independent front suspension. They attach the control arms to the vehicle frame in a way that permits the wheels to move up and down independently. The control arm bushings provide the bearing for this hinge. The bushings must be in satisfactory condition to perform their primary function of keeping the control arms in the proper position to maintain alignment settings. The rubber torsion type also has an important secondary function of helping dampen road shock from the vehicle body.

Visually inspect each bushing assembly. The first sign of failure in the rubber torsion-type bushing is when cracks appear around the bushing edges. Small cracks on the outer surface are not harmful, but the bushing should be checked very closely when they are present. Look for severe compression of the rubber on one side or the rubber extruding out of the bushing. Also, check for torn rubber and frayed edges. When you examine control arm bushings, also look carefully at the end nuts. They can work loose and allow the bushing to pop out of the mounting.

Coil springs become weakened through constant twisting and flexing in normal service. This allows them to sag, lowering the vehicle out of its normal curb height range. When the curb height varies by even a fraction of an inch from the original specifications, there are problems. Suspension parts, such as control arms and ball joints, may be extremely overloaded when there is not enough suspension travel.

Coil springs are checked by taking measurements at specific points on the vehicle. The measuring points and specifications can be found in the vehicle shop service manual. The springs can also be checked by comparing measurements taken on each side of the car. Measure dimension A; this is the distance between the lower control arm and the frame. There should be a difference of no more than 1/4 inch (6 mm) between the right and left side of the car. Measure dimensions B and C (from ground level to the center of pivot points). The difference between B and C on either side should not be more than 3/4 inch (19 mm). Make sure the bumper is not bent or deformed; then measure distance D, which is the height from a level floor to the bottom of the bumper. The difference between the D measurements should not be more than 3/8 inch (10 mm). If you find your measurements are beyond specifications, both coil springs should be replaced.

Many vehicles are equipped with strut rods that are bolted to the lower control arm and mounted at the opposite end through the strut rod bushing in the vehicle frame. Strut rods act as a brace for the lower control arm. The strut rod bushing must maintain a firm, flexible shock-absorbing mount.

The strut rod bushings wear due to the constant flexing of the strut rod and rubber deterioration caused by the elements. The results are changeable alignment settings, noise (especially during braking), and pulling to the side during braking.

Strut rod bushings wear from the inside out. A check of the external bushing condition will not help determine if the bushing needs replacing. The best way to check strut rod bushings is to raise the car on a hoist with a helper inside. Spin one of the front wheels and then have the person in the car apply the brakes. Worn strut rod bushings will make a popping noise when the brakes are applied. This noise is due to movement in the bushing assembly as the strut tries to control braking forces on the control arm.

Sway bar bushings anchor the bar to the vehicle frame and the control arm on each side. The purpose of the bar is to reduce body roll and sway. The condition of the bushings will affect the performance of the bar. Check the bar for missing links. Inspect the frame bushings for tightness, distortion, and signs of movement by grabbing the bar with your hand and trying to shake it.

Lubricate Suspension and Steering Components

In years past a "lube job" or "grease job" was a popular and profitable service procedure. Most vehicles had numerous lubrication points that a technician had to locate and then lubricate or grease. Due to advances in lubricant quality and sealing technology, many of the areas that once required lubrication are now permanently sealed. There are, however, some current vehicles that have a few suspension or steering lubrication points.

CAUTION: Air-operated lube guns inject grease through the nozzle at high pressures. Always wear eye protection when using a lube gun. Never point the grease gun at any part of your body because the grease could be injected through your skin.

The ball joints and some types of steering linkages require a grease-type lubricant between the moving parts. Grease is a liquid lubricant that is mixed into a binder material to make it thick.

The grease is injected into a lubrication area with a grease or lube gun. There are two types of lube guns: mechanically operated and air operated. The hand pump-type lube gun is shown below. Grease is stored in a cartridge inside the gun. Pumping the handle causes grease to come out the nozzle under pressure. The air-operated lube gun is often a large roll around unit. Many have a large container of grease that is pressurized by shop air. The nozzle has a trigger, which when activated, allows air to force grease through the grease hose and out the gun nozzle. The grease comes out the nozzle under high pressure.

The nozzle on the lube gun is made to fit on lubrication fittings. The fitting is a small part that screws into the part requiring lubrication. It has a small round valve inside that keeps dirt out of the part. The lube gun nozzle fits tightly over the end of the fitting. When the grease is pumped through the nozzle under pressure, it forces the fitting valve open and allows grease to enter the part.

When you do a suspension and steering lubrication, first look up the location of all the lubrication fittings on the car. Most shop service manuals have a chart that identifies the lubrication points on the suspension and steering. . There are usually two fittings on each side of the car. One on the lower ball joint and one on the steering tie rod. To do the lubrication job, raise the car on a hoist or support it on safety jack stands. Wipe each lubrication fitting clean with a rag. Inspect the grease seals for leaks or tears. You will have to remove these plugs and temporarily install lubrication fittings.

WARNING: If you do not clean a lube fitting before inserting the lube gun, dirt can be forced through the fitting and into the part. Dirt will cause the part to fail early.

Push the lube gun nozzle over the fitting. The nozzle must fit over it completely or the grease will not enter the fitting. Make sure your gun does not deliver lube at too high a pressure because this could rupture the ball joint seals. Work the pump or squeeze the trigger slowly. The grease should enter the fitting and not leak out around the end of the nozzle. If the grease leaks around the end of the nozzle, you probably have one of two problems:

You do not have a good fit between the nozzle and fitting. Clean the fitting and try again. The fitting may be plugged. Install a new fitting and try again. One or two hand pumps or squeezes of the trigger is enough to lubricate the typical ball joint. You should not see evidence of lubricant escaping past the seals. Remove the nozzle from the fitting. Wipe off any excess grease from the fitting area. Repeat this procedure for each of the lubrication fittings on the car.

WARNING: Do not overfill a lubrication area with grease. If you force too much grease into a ball joint, you can blow out the seal. If you rupture the seal, the ball joint assembly will have to be replaced.

Repair Guide: Steering Basics and Steering Types

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Inspection and maintenance of the steering system is important because a steering problem can lead to an accident. The steering system has two critical inspection and maintenance areas: the steering gear and the steering linkage. Two basic types of steering gears are in use. One is the recirculating ball type and the other is the rack-and-pinion type. Both may be operated manually or with the aid of hydraulic power. The next sections describe the parts and operation of the manually operated steering gears.

Recirculating Ball and Nut Steering Gear

The larger and heavier the car, the more difficult it is to steer. Most large American cars are equipped with a recirculating ball-type steering gear. This type of steering gear is very low in friction and provides a good mechanical advantage for a heavy vehicle.

The recirculating ball and nut steering gear consists of several parts contained in a steering gear housing. The steering gear shaft is connected to the steering wheel either directly or through some type of flexible joint. There is a worm gear on the end of the steering gear shaft. A cross (Pitman) shaft is mounted in the housing in a position 90 degrees to the worm gear. A ball nut rides on the worm gear and a gear on the cross (Pitman) shaft, called the cross shaft sector, is engaged with this nut.

Ball or roller bearings are used to support both ends of the worm gear and are adjustable to remove end or side play from the worm gear. The cross (Pitman) shaft is supported by bushings, needle bearings, or a combination of the two, and provision is made to control the worm and cross shaft clearance. All parts are enclosed in a cast housing that is partly filled with lubricant. Seals are used to prevent the entry of dirt or the loss of lubricant. Provision is made to bolt the steering gear housing to a rigid area, usually the frame.

The ball nut has internal threads that are meshed to the threads of the worm with continuous rows of ball bearings between the two. The ball bearings are recirculated through two outside loops, called ball guides.

The sliding ball nut has tapered teeth cut on one face

that mate with teeth on the sector. As the steering wheel is rotated, the nut is moved up or down on the worm. Because teeth on the nut are meshed with the teeth on the sector, the movement of the nut causes the sector shaft to rotate and swing the steering linkage connected to it.

The recirculating ball construction results in a friction-free contact between the nut and the worm. When the steering wheel is turned to the left, the ball bearings roll between the worm and the nut and work their way upward in the worm groove. When the ball bearings reach the top of the nut, they enter two ball guides and are directed downward into the worm groove at a lower point. When the steering wheel is turned to the right, the ball bearings circulate in the opposite direction.

Rack-and-pinion Steering Gear

The recirculating ball steering gear has the disadvantage that it occupies a good deal of space, usually in the engine compartment. The rack-and-pinion steering gear was first developed for compact cars in which the engine compartment space was limited. The rack-and-pinion system has worked so well that it is currently being used in both imported and American compacts and intermediate size cars.

The steering wheel and steering shaft are connected to a pinion gear. The pinion gear is in mesh with a straight bar that has gear teeth cut into one side. The toothed bar is called a rack. When the driver turns the steering wheel, the pinion gear turns, causing the rack to move. This movement, in turn, is connected to a linkage that moves the front wheels.

The rack-and-pinion gear is mounted in a rack housing assembly. The steering linkage consists of two inner tie rods and two tie rod ends. The inner tie rod ends are attached to the steering rack ends. The outer tie rod ends are attached to the suspension arms on the steering knuckles. Rubber boots are used to cover and protect the inner tie rod assemblies from road splash.

Steering Linkage

With a rack-and-pinion steering gear, the rack is connected by linkage directly to the steering knuckle. Recirculating ball-type steering gears require a more complicated linkage to change the rotary output of the sector shaft to the back-and-forth movement of the wheels. A steering linkage consists basically of a steering gear Pitman arm, a centerlink, and a tie rod assembly connected to each other by ball sockets. The Pitman arm is splined on the steering gear sector shaft. When the sector shaft turns, the Pitman arm swings in an arc. The swinging end of this arm is connected to the center link.

The center link (also called drag link or relay rod) transfers the swinging motion of the gear arm to a linear or back-and-forth motion. It can also change the direction of the sector shaft arm motion, depending on the type of linkage. The center link is connected to the tie rods. These transmit movement of the relay rod to the steering arms. The steering arms are part of, or attached to, the steering knuckle spindle assemblies. When the steering arm moves, the steering knuckle assembly rotates on the suspension control arm ball joints.

Tie rod ends are used to connect the tie rods to the center link and to the steering arms. They are also used on the end of the sector shaft arm and the idler arm. Adjustment of the tie rod length is provided in threaded sleeves that are locked by clamps.

A tie rod end is a ball located in a socket. The ball is attached to a tapered stud. A spring or plastic spacer holds the ball in position in the socket. The tapered stud fits into a taper in a steering arm and is held in position by a threaded nut. The ball and socket allows up-and-down movement between the tie rod and the steering arm as the car goes over bumps. The ball and socket also allows back-and-forth movement as the driver turns the steering wheel. Grease is held between the ball and socket with a grease seal.

In most steering linkage arrangements, one end of the center link is supported in the Pitman arm. The other end is supported by a frame-mounted idler arm. The idler arm pivots in a support attached to the frame when the steering linkage moves back and forth.

WARNING: All steering linkage parts are manufactured from malleable materials and will bend, distort, or deflect rather than fracture under extreme shock loads. This toughness and malleability are necessary to avoid the complete loss of control that would occur if any part of a steering linkage were to break. Steering linkage parts must never be heated during a repair because this could cause them to lose their malleability and, as a result, fracture.

Repair Guide: Shock Absorber and Strut Operation

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A shock absorber, or strut, is basically a hydraulic damping mechanism for controlling spring vibrations. It will not support weight or return to its original position after it is moved; only a spring will do that. The car body is therefore suspended on springs and the shock absorber is used to control its movements when the springs are deflected by bumps and caused to vibrate.

Shock absorbers control spring movements in both directions: when the spring is compressed and when it is extended. The amount of resistance needed in each direction is determined by the type of vehicle, the type of suspension, the location of the shock absorber in the suspension system, and the position in which it is mounted.

Shock absorbers control suspension vibrations by absorbing the energy stored in the spring when it is compressed and converting that energy into heat. This controls the spring reaction and allows that spring to return to its original position slowly and without a rapid or violent movement. The shock absorber dispels the heat from the converted energy into the air passing around it.

Shock absorbers develop control or resistance.

A shock absorber, or strut, is basically a hydraulic damping mechanism for controlling spring vibrations. It will not support weight or return to its original position after it is moved; only a spring will do that. The car body is therefore suspended on springs and the shock absorber is used to control its movements when the springs are deflected by bumps and caused to vibrate.

Shock absorbers control spring movements in both directions: when the spring is compressed and when it is extended. The amount of resistance needed in each direction is determined by the type of vehicle, the type of suspension, the location of the shock absorber in the suspension system, and the position in which it is mounted.

Shock absorbers control suspension vibrations by absorbing the energy stored in the spring when it is compressed and converting that energy into heat. This controls the spring reaction and allows that spring to return to its original position slowly and without a rapid or violent movement. The shock absorber dispels the heat from the converted energy into the air passing around it.

Shock absorbers develop control or resistance by forcing fluid through restricted passages. There are usually four shock absorbers on a car. One is located near each wheel. They are called direct acting because of their direct connection between the car frame (body) and the axle (wheel-mounting member). Shock absorbers are also called double acting because they control motion in both directions of the suspension travel. Upward movements of the body are called rebound and downward movements are called compression.

The upper shock mounting is attached to a piston rod. The piston rod is attached to a piston and rebound valve assembly. A rebound chamber is located above the piston and a compression chamber below the piston. These chambers are full of hydraulic fluid. A compression intake valve is positioned in the bottom of the cylinder and connected, hydraulically, to a reserve chamber also full of hydraulic fluid. The lower mounting is attached to the cylinder tube in which the piston operates.

During compression, the movement of the shock absorber causes the piston to move downward with respect to the cylinder tube, transferring fluid from the compression chamber to the rebound chamber. This is accomplished by fluid moving through the outer piston hole and unseating the piston intake valve.

During rebound, the pressure in the compression chamber falls below that of the reserve chamber. As a result, the compression valve will unseat and allow fluid to flow from the reserve chamber into the compression chamber. At the same time, fluid in the rebound chamber will be transferred into the compression chamber through the inner piston holes and the rebound valve.

Gas-filled Shock Absorbers

The rapid movement of the fluid between the chambers during the rebound and compression strokes can cause foaming of the fluid. Foaming is the mixing of free air and the shock fluid. When foaming occurs, the shock develops a lag because the piston is moving through an air pocket that offers up resistance. The foaming results in a decrease of the damping forces and a loss of spring control.

During the movement of the piston rod, the fluid is forced through the valuing of the piston. When the piston rod is moving quickly, the shock absorber oil cannot get through the valuing fast enough, which causes pressure increases in front of the piston and pressure decreases behind the piston. The result is foaming and a loss of shock absorber control. The gas-filled shock absorber is designed to reduce foaming of the oil. The gas-filled shock absorber uses a piston and oil chamber similar to other shock absorbers. The difference is that instead of a double tube with a reserve chamber, a dividing piston separates the oil chamber from the gas chamber. The oil chamber contains a special hydraulic oil, and the gas chamber contains nitrogen at 25 times atmospheric pressure.

When the piston rod is moved into the shock absorber, oil is displaced, as in the double-tube principle. This oil displacement causes the dividing piston to press on the gas chamber, thus reducing it in size. With the return of the piston rod, the gas pressure returns the dividing piston to its starting position. Whenever the oil column is held at a static pressure of approximately 25 times atmospheric pressure, the pressure decreases behind the working piston cannot be high enough for the gas to exit from the oil column. Consequently, the gas-filled shock absorber operates without foaming.

Shock Absorber Ratio

Shock absorber control or resistance is expressed as a ratio, such as 90/10, 70/30, or 50/50. There has been no standard usage of the number sequence in the ratio. Shock absorber technicians commonly express the extension control first. A 90/10 ratio means that 90% of the shock's control is in the compression cycle and 10% of the control is in the extension cycle.

Inspect Suspension Components for Wear

SERVICE TIP: One of the best ways to diagnose a suspension problem is to go for a ride with the owner. Observe what the car is doing. Ask yourself if the problem occurs during braking, steering, or over bumps. Your observations will help you a great deal when you inspect the suspension system.

Anytime you have a car on a hoist to lubricate the suspension components, you should also check the suspension parts for wear. A car with poor steering control, rapid tire wear, noise during stopping and driving over bumps, or poor steering stability may have a suspension, steering, or wheel alignment problem. You should follow a systematic step-by-step procedure to determine the condition of the parts in each of these areas.

To begin your inspection, raise the vehicle on a hoist so you have plenty of room to make an inspection. You can test for loose wheel bearings by grasping the front tire top and bottom and rocking it in and out. Any noticeable looseness is too much. To make sure any looseness detected is in the wheel bearing, check for relative movement between the rotor or brake drum and backing plate. Upper and lower ball joints on most vehicles perform different functions. They are designed differently and require different inspection techniques. The design differs because one pair, called the weight carriers, always supports the front half of the vehicle weight. The other set, called the friction or follower joints, supports no vertical load, but must maintain a firm, quiet connection between the spindle and the control arm. On most American cars with short, long arm suspension, the lower ball joint is the weight carrier. But on many import models with short, long arm suspension, the upper ball joint carries the load.

To apply the proper checking procedure, identify which ball joints are the weight carriers and which are the friction joints. The weight carrier is always mounted on the control arm to which the coil spring or torsion bar is mounted. The friction joint is always mounted on the unloaded control arm. After identifying the ball joints by function, continue the inspection.

Friction ball joints have a heavy coil spring or rubber insert inside that preloads the ball stud and enables the spring to dampen the vibration and road shock of the wheels. Unfortunately, the spring also makes the ball joints difficult to check because the preload keeps the ball joint tight and makes a simple wheel shake test unreliable. The most accurate way to check a friction joint for wear is to disconnect it from the spindle, put two nuts back on the stud to act as a lock, and turn the stud with an inch-pound torque wrench. If you get a reading between 24 and 96 inch-pounds (2-8 newton-meters) for most cars, the ball joint is in satisfactory condition. When the reading is above or below these limits, something is wrong in the socket and the ball joint should be replaced. This checking procedure should be followed when the vehicle has very high mileage, has performed in especially rough service, or appears not to have had proper maintenance.

Weight-carrying ball joints are constantly twisting and turning in response to the steering and up-and-down motion of the front wheels. This wearing motion continues while the two ball joints are loaded with the vehicle weight.

To check a weight-carrying ball joint, first visually check for the general condition of the ball joint and seal. Then check to determine the amount of wear on the inside of the part. Look for broken seals that let contaminants into the part, which shortens the life of the joint. When possible, check the throat area under the seal for cracks or distortion.

The next step is to unload the ball joint and measure the amount of clearance. Lower the car to the ground and position a jack to unload the suspension. For lower weight carriers, place the support under the lower control arm near the wheel.

For upper weight carriers, place the support under the frame crossmember and support the upper control arm in its operating position with a wedge between the body and upper control arm. Check for loose wheel bearings and adjust if necessary. Wheel bearings must be snug to avoid adding their clearance to that of the ball joints.

The most accurate way to measure internal wear is by using a dial indicator that can measure vertical movement right at the ball joint socket. This eliminates the chance of adding other clearances, such as those created by loose wheel bearings, to the ball joint check measurement. The dial indicator is mounted on the lower control arm, near the ball joint to be checked, with locking pliers or a clamp. The dial indicator plunger is then placed against the ball joint steering knuckle (depending on the type of car being checked) so it can read the vertical movement of the parts when the ball joint is unloaded and the wheel is moved through its full vertical range with a pry bar.

Lock the indicator in place by tightening the flexible coupling. Set the dial indicator to zero. Place the pry bar between the tire and ground and pry up on the bottom of the tire. Then, when the wheel is moved vertically through its full range, the reading shown on the dial indicator will equal the amount of internal ball joint clearance. Compare your readings to specifications in the shop service manual to determine if the ball joint should be replaced.

The lower ball joint is the only ball joint on MacPherson strut units. To check it, grasp the lower arm near the ball joint and force the arm up and down to check for looseness, or push and pull on the tire near the ball joint. If there is any movement, the ball joint should be replaced.

Many vehicles use ball joints with built-in wear indicators. Wear indicator-type ball joints must remain loaded to check for wear. The vehicle should be checked with the suspension at curb height. The most common type of wear indicator has a small diameter boss that protrudes from the center of the lower housing. As wear occurs internally, this boss will gradually recede into the housing. When it is flush with the housing, the ball joint should be replaced.

You are ready now to visually check each of the control arm bushing assemblies. Control arm cross shafts and bushings provide the inner hinges for the independent front suspension. They attach the control arms to the vehicle frame in a way that permits the wheels to move up and down independently. The control arm bushings provide the bearing for this hinge. The bushings must be in satisfactory condition to perform their primary function of keeping the control arms in the proper position to maintain alignment settings. The rubber torsion type also has an important secondary function of helping dampen road shock from the vehicle body.

Visually inspect each bushing assembly. The first sign of failure in the rubber torsion-type bushing is when cracks appear around the bushing edges. Small cracks on the outer surface are not harmful, but the bushing should be checked very closely when they are present. Look for severe compression of the rubber on one side or the rubber extruding out of the bushing. Also, check for torn rubber and frayed edges. When you examine control arm bushings, also look carefully at the end nuts. They can work loose and allow the bushing to pop out of the mounting.

Coil springs become weakened through constant twisting and flexing in normal service. This allows them to sag, lowering the vehicle out of its normal curb height range. When the curb height varies by even a fraction of an inch from the original specifications, there are problems. Suspension parts, such as control arms and ball joints, may be extremely overloaded when there is not enough suspension travel.

Coil springs are checked by taking measurements at specific points on the vehicle. The measuring points and specifications can be found in the vehicle shop service manual. The springs can also be checked by comparing measurements taken on each side of the car. Measure dimension A; this is the distance between the lower control arm and the frame. There should be a difference of no more than 1/4 inch (6 mm) between the right and left side of the car. Measure dimensions B and C (from ground level to the center of pivot points). The difference between B and C on either side should not be more than 3/4 inch (19 mm). Make sure the bumper is not bent or deformed; then measure distance D, which is the height from a level floor to the bottom of the bumper. The difference between the D measurements should not be more than 3/8 inch (10 mm). If you find your measurements are beyond specifications, both coil springs should be replaced.

Many vehicles are equipped with strut rods that are bolted to the lower control arm and mounted at the opposite end through the strut rod bushing in the vehicle frame. Strut rods act as a brace for the lower control arm. The strut rod bushing must maintain a firm, flexible shock-absorbing mount.

The strut rod bushings wear due to the constant flexing of the strut rod and rubber deterioration caused by the elements. The results are changeable alignment settings, noise (especially during braking), and pulling to the side during braking.

Strut rod bushings wear from the inside out. A check of the external bushing condition will not help determine if the bushing needs replacing. The best way to check strut rod bushings is to raise the car on a hoist with a helper inside. Spin one of the front wheels and then have the person in the car apply the brakes. Worn strut rod bushings will make a popping noise when the brakes are applied. This noise is due to movement in the bushing assembly as the strut tries to control braking forces on the control arm.

Sway bar bushings anchor the bar to the vehicle frame and the control arm on each side. The purpose of the bar is to reduce body roll and sway. The condition of the bushings will affect the performance of the bar. Check the bar for missing links. Inspect the frame bushings for tightness, distortion, and signs of movement by grabbing the bar with your hand and trying to shake it.

Inspect and Test Shock Absorbers and Struts

Whenever you inspect the suspension system, you should test the shock absorbers or MacPherson struts. The test should be performed with the car on the ground, not when the car is being supported on a jack or hoist.

The way to test the front and rear shocks or MacPherson strut cartridges is by bouncing each corner of the car. Rock the car at each corner and release. If the car bounces more than 1 1/2 times after you have stopped, take a closer look at the shocks or cartridges.

If the car bounces more than it should, raise the car back up on the hoist. Run your hand over the tire tread completely around the tire and from inside to outside. Cupping or unusual wear in any area indicates the shocks may not be holding the tires on the road. Look for broken mounts, damaged bushings, and oil on the shock absorber barrel. Grab the shock and shake firmly. This may reveal damage to a mount or bushing not apparent at first sight. Substantial fluid on the outside of the shock absorber housing indicates a leaking seal. Fluid cannot be replaced and shocks are ineffective without fluid; shock absorber replacement is required. Shocks should always be installed in pairs, and it is often most economical to replace all four. One indicator of a need to replace the MacPherson strut/shock is oil leakage at the piston rod seal. Also conduct a bounce test. During the bounce test, carefully observe the top strut mount. Any noise or movement here can indicate the need for parts replacement.

Remove and Replace Shock Absorbers

When replacing front or rear shocks, first compare the shocks on the car to the replacement units. The old and new shocks should be the same length and same mounting; carefully observe the position and type of mounting of the original shock absorbers.

There are three common styles of shock mountings. The shock absorber can be mounted by a thread formed on the end of the piston shaft. This is called a stem mounting. Stem mounting is common on the top end of a shock mounted in the center of a coil spring. The tab stud or cross pin mount is used on the bottom of many coil spring-mounted shock absorbers. Sleeve mounting may be used on one or both ends of the shock absorber; it is used on some front shocks, but is most common on the rear.

Before removing any shock absorber hardware, spray penetrating fluid on all the threads. Road splash and rust can make nuts very difficult to remove. Some nuts will probably have to be removed with an air impact wrench and impact socket.

To remove front or rear shock absorbers, raise the car on a hoist. Do not allow the front or rear drive axle to hang--make sure it is supported on the hoist.

To remove the typical stem and cross pin-mounted front shock absorber, use an open-end wrench to hold the shock absorber stem. Remove the nut, then remove the upper washer and grommet. Unbolt the cross pin from the lower control arm and pull the shock absorber out through the bottom of the control arm.

Make sure the correct number and type of lower rubber grommets and washers are positioned on the stem. Check the instructions with the new shocks and also compare with the old shock mounting. Push the new shock absorber into position through the hole in the bottom control arm. Install the upper washer and grommet, then install the nut. Use an open-end wrench to hold the stem and torque the nut to specifications. Install the bolts that hold the cross pin and torque them to specifications.

Rear shocks are often mounted with a stud or cross pin at one end and a sleeve mount at the other end. The stud and cross pin are removed and replaced by the procedure described earlier for front units. The sleeve mount is removed and replaced by removing and replacing the bolt and nut that goes through the sleeve into the mounting bracket. Be sure to torque all the attaching bolts to specifications.

Repair Guide: Power Steering

2008-01-30T13:24:00.000-08:00

Most cars today are equipped with a power steering system. Many power steering systems use hydraulic power. These systems use a power steering pump driven by a belt from the crankshaft. The pump moves fluid under pressure through hoses to the steering gear. The pressure is used in the steering gear to reduce steering effort. A reservoir for fluid is attached to the rear of the pump. Checking the fluid level in this reservoir is a common under hood maintenance job.

The fluid used in the power steering system must be the correct type for the vehicle. Always check the owner's manual for the correct type of fluid. Older vehicles use automatic transmission fluid in the power steering systems. New vehicles use special power steering fluids. These fluids meet the special requirements of the power steering system. They are often a different color from automatic transmission fluid so that leak detection is easier.

Q & A: Power steering

1. My steering feels loose. Any idea why?

Answer:

The most common causes of steering looseness include worn tie rod ends, a worn idler arm or center link (on vehicles without rack and pinion steering), a worn steering gear or a worn steering rack.
Normally, your steering wheel should have no more than about a quarter inch of play. Any more means something is worn or loose and needs to be fixed.

WARNING: Don't put off having your steering looked at because a failure of a critical component could cause loss of steering control!

The inner and outer tie rod ends should have no perceptible looseness. Worn or loose tie rod ends are especially dangerous because if one pulls apart you'll lose steering control. Worn tie rod ends can also cause rapid tire wear.

If you have a rear-wheel drive vehicle with conventional steering (not rack and pinion steering), the idler arm should have no more than the specified amount of maximum play. Refer to a manual for the specs and recommended procedure for checking it. Checking idler arm play usually involves pulling on the arm with a specified force and measuring how much the arm deflects.

If your vehicle has a lot of miles on it, the steering gear or rack itself may be worn. On conventional steering boxes, there's usually an adjustment screw that can be used to take some of the slack out of the system. With rack and pinion steering, though, adjustment is usually little help because the rack develops center wear. If the pinion is adjusted to compensate, the rack may bind when turned to either side. The only cure for a center wear condition is to replace the rack with a new one (an entire new rack assembly).

OTHER CAUSES

Sometimes the steering will feel loose because of a worn U-joint coupling in the steering column. Loose or worn wheel bearings can also make the steering wander and feel loose.

2. Power steering feels stiff when I first start the car, but feels normal after I've driven awhile. Why?

Question:

My power steering feels stiff when I first start my car, but then feels normal after I've driven the car awhile. How come?
Answer:

This is called "morning sickness" and has nothing to do with being pregnant. The condition is caused by wear in the spool valve housing on certain power steering racks -- notably GM front-wheel drive cars.
When the car is first started, the rack is cold and clearances in the spool valve are at their greatest. Hydraulic pressure from the power steering pump leaks past grooves worn in the aluminum spool valve housing. This causes a loss of pressure and increases steering effort. The steering feels stiff with little or no power assist. As the car is driven, the rack warms up. This decreases the clearances inside the spool valve housing, which reduces the leakage past the grooves. More pressure goes to where it is supposed to go and the steering becomes easier as power assist returns.

The "fix" for this condition is to replace the rack with a new one (preferably with a cast iron spool valve housing) or a remanufactured rack that has a stainless steel sleeve pressed into the aluminum housing.

Repair Guide: Rear Suspension

2008-01-30T13:22:00.001-08:00

When the vehicle has a front engine and front drive, the rear wheels are usually suspended independently from a rear crossmember by arms that go to the back or trail the mounting points. This is called a trailing arm independent rear suspension. Wheel spindles are attached to the two trailing arms, which extend rearward from mounting points on the body where they are attached with rubber pivot bushings. A crossmember is welded between the two trailing arms just behind the pivot bushings. This crossmember, working with the two trailing arms, provides an anti-sway-type stabilization for the rear suspension.

Many trailing arm suspension designs use coil springs surrounding vertical shock absorbers. The shock absorbers are attached at points inboard of each spindle and extend upward to rubber isolated mounting points above the rear wheel wells in the body. Other systems use separately mounted shocks, springs, and sway bar.

Rigid Rear Suspension

The suspension system for rear drive vehicles must provide up-and-down wheel movement as well as provide the space for drive axles. For many years, American vehicles have used a design called the rigid rear suspension system to solve this problem. This suspension system is designed around the rear axle housing. There are two basic disadvantages to this system, however. First, because both rear wheels are connected rigidly to the axle housing, movement up or down by one wheel affects the other. Second, this design also has a large amount of unsprung weight.

There are two basic designs of rigid rear suspension systems. One uses a leaf spring to spring and locate the axle housing. The other uses a coil spring and some type of control arm assembly.

Two rubber bushed lower control arms mounted between the axle assembly and the frame maintain the fore-and-aft relationship of the axle assembly to the frame. Two rubber bushed upper arms control driving and braking torque and sideways movement of the axle assembly. The rigid axle holds the rear wheels in proper alignment.

The upper control arms are shorter than the lower arms, causing the rear axle housing to rock and tilt forward on compression. This rocking or tilting lowers the rear drive shaft to make possible the use of a lower tunnel in the rear floor pan area. The upper arms control drive forces and side sway.

The coil springs are located between brackets on the axle tube and spring seats in the frame. They are held in the brackets and spring seats by the weight of the car and by the shock absorbers, which limit axle movement during rebound. Ride control is provided by two shock absorbers angle mounted between brackets attached to the axle housing and the rear spring seats.

The rear axle housing is attached to leaf springs by U-bolts. The spring front eyes are attached to the frame at the front hangers through rubber bushings. The rear ends of the springs are attached to the frame by the use of shackles, which allow the spring to change its length while the vehicle is in motion. A stabilizer bar is used to control body sway. Control arms are not required with leaf springs.

Independent Rear Suspension

The high poor handling characteristics of the rigid rear suspension system has led to the development of a number of independent rear suspension designs for rear drive cars. Basically, these designs are the same as the short, long arm; MacPherson strut; and trailing arm systems described previously. The main difference is providing for the mounting of the differential and drive axle assembly. The suspension system shown below allows each rear wheel to move up and down independently of the other. Two large trailing lower control arms support the wheel assembly. The differential is mounted to the frame and is sprung weight. The movement of the control arms is controlled by coil springs and shock absorbers between the control arms and the frame.

Another type of rear independent suspension uses a MacPherson strut attached to a lower control arm to get independent action of each wheel.

Question:

1. My mechanic says my car needs ball joints. Please explain.
Answer:

Ball joints are a part of your vehicle's suspension that connects the steering knuckles to the control arms. A ball joint is essentially a flexible ball and socket that allows the suspension to move and at the same time the wheels to steer. Cars and trucks without strut suspensions typically have four of them (one upper and one lower on each side). Cars and minivans with strut suspensions have only two (one lower ball joint on each side). Some front-wheel drive cars also have ball joints on the rear suspension.
Ball joint locations in front end

Like any other suspension component, ball joints eventually wear and become loose. Excessive play in the joint can affect wheel alignment and tire wear. Loose joints can also cause suspension noise (typically a "clunking" sound when hitting a bump).

WARNING: If a ball joint fails, the suspension can collapse causing a loss of control. So don't put off having a bad set of joints replaced.

JOINT INSPECTION

Joints should be inspected before they're greased (since grease takes up some of the slack in the joint). Ball joints are pretty easy to check, but each type requires a different inspection procedure. Use the wrong procedure and you'll get misleading results. The procedure that needs to be used depends on the location and loading of the joint:

* LOWER LOAD CARRYING ball joints are found on front- and rear-wheel drive vehicles where the coil spring or torsion bar is on the lower control arm. You'll also find them on the rear suspension of 1985 & up FWD Buick, Cadillac, Pontiac & Oldsmobiles, too.

Joints with built-in wear indicators (most GM and Ford RWD cars, rear joints on the FWD GM cars, and GM RWD vans, S10 & S15 Blazer) must be checked with the full weight of the vehicle on the tires on the shop floor or on a drive-on style ramp -- not with the wheels up or the suspension supported by jack stands.

No measurements are required if a joint has a wear indicator because internal play is indicated by the position of the grease fitting boss. The boss protrudes about .050 inches on a new joint. As the joint wears, the boss recedes into the housing. The joint is considered "good" as long as you can see or feel the edge of the boss protruding from the housing. But if the top of the boss is flush or below the housing, it's time to replace the joint.

On lower load carrying ball joints without a wear indicator, the joint is checked in the unloaded condition with the wheel raised off the ground and the lower control arm supported by a jack stand. A dial indicator is then used to measure play in one of two directions: sideways (horizontal or radial play) or vertically (axial or up-and-down play). The direction to measure depends on the application (refer to a manual for the exact specs).

Sideways play is measured with the indicator positioned against the inside of the wheel rim near the joint. The wheel should be pushed in and out by hand to check sideways play, and lifted with no more than 25 lbs. of force to check vertical play. Many joints allow up to .250 in. of sideways (radial) play, but some allow no play or only .015 in. of play. Always refer to the vehicle manufacturer's specs.

Vertical play is measured with the dial indicator positioned against the knuckle stud nut (Ford & GM) or the joint housing (Chrysler). A joint that has more than .050 in. of vertical play doesn't necessary require replacement because the specs range from zero play to as much as .125 inch of play.

The most common mistake that's made here is to use too much pressure on a pry bar or to insert a pry bar between the control arm and knuckle rather than under the wheel. Pry hard enough and any joint may appear to be bad.

* LOWER FOLLOWER NONLOADED ball joints are found on two kinds of applications: RWD cars where the spring is over the upper control arm, and vehicles with MacPherson strut suspensions. On both applications the lower joint is checked with the wheel raised off the ground hanging free (no stand under the lower control arm). Rock the wheel in and out by hand. A good joint should show no movement.

One exception here is 1978-80 Omni & Horizon which allows up to .050 inch of sideways play. Another exception is Chrysler FWD minivans and FWD cars ('81 & up). On these applications, the lower joint has a wear indicator grease fitting. Joint play is checked with the wheels on the ground rather than raised. If the grease fitting can be twisted with your fingers, the joint needs to be replaced.

* UPPER LOAD CARRYING ball joints are found on vehicles where the spring or torsion bar is on the upper control arm. Like the lower follower nonloaded ball joints, the upper joints are checked in the unloaded condition with the wheels off the ground -- but with a wedge or block between the frame and upper control arm to support the upper arm. On most applications, any movement calls for replacement. But on some Fords, up to .250 in. of radial play is allowed.

* UPPER FOLLOWER NONLOADED ball joints are also checked with the wheels off the ground but with the lower control arm supported. Any movement usually calls for replacement.

JOINT REPLACEMENT

Any joint that exceeds the vehicle manufacturer's maximum allowable wear needs to be replaced. The greater the amount of wear, the greater the urgency to replace it.

Ball joints are often replaced in complete sets, or at least in matched pairs on both sides (both lowers or both uppers). This is because the joints on both sides of a vehicle usually have the same amount of wear. If one is bad, the other usually is too. Load carrying ball joints usually wear out before ones that don't carry a load, so it may only be necessary to replace the loaded joints instead of the complete set.

Replacing a set of ball joints requires separating the control arms from the steering knuckles, a job which can be difficult depending on the design and age of the vehicle. At the very least, it usually requires a special "ball joint fork" tool to loosen the ball joint stud from the knuckle. If this sounds like more of a a job than you want to tackle, let a professional do it the work.

Question:

2. I feel a high speed shimmy in the steering wheel. What's causing it?
Answer:

A high speed shimmy is usually caused by a wheel that's out of balance or a bent wheel.
The first thing to check for would be a bent wheel. Raise the front of the vehicle off the ground and rotate each wheel by hand. If you see any sideways or in and out movement of the wheel, it is bent and needs to be replaced.

WARNING: Although some people claim they can straighten bent wheels, doing so is risky -- especially with aluminum alloy wheels. Replacement is the safest option (but also expensive).

If you don't see any sideways movement in the wheel, it doesn't necessarily mean the wheel is straight. There may be just enough sideways runout to cause a shimmy, but not enough to see. To find this kind of problem, you'll need a dial indicator. More than about .050 inch of sideways runout can be enough to cause a problem.

If the wheels seem to be straight, have the balance of both wheels checked (or rebalanced). If that fails to cure the shimmy, you may have some kind of tire problem due to defective belt alignment or tire construction. Other causes may include loose or improperly adjusted wheel bearings, insufficient caster alignment (check and readjust alignment as needed), or a worn steering damper (on trucks or other vehicles equipped with a steering stabilizer).

Repair Guide: Front Suspension

2008-01-30T13:19:00.000-08:00

Most suspension systems utilize a spring and shock absorber. Suspension systems differ in the type and arrangement of the linkages used to connect these elements to the frame and wheel. The unequal length control arm or short, long arm (SLA) suspension system has been common on American vehicles for many years. Because each wheel is independently connected to the frame by a steering knuckle, ball joint assemblies, and upper and lower control arms, the system is often described as an independent suspension. The short, long arm suspension system gets its name from the use of two control arms from the frame to the steering knuckle and wheel assembly. As shown, these two control arms are of unequal length with a long control arm on the bottom and a short control arm on the top. The control arms are sometimes called A arms because in the top view they are shaped like the letter A.

The short, long arm suspension is designed so that the wheel and tire assembly tends to rise and fall vertically as it goes over bumps in the road. The unequal length control arms compensate for jounce (upward movement of the wheels) and rebound (downward movement of the wheels). For example, if the front wheels hit a bump, as shown below, the wheel and tire assembly move upward in a jounce movement. To offset this movement, the upper control arm is made shorter so the arc it travels is shorter than that of the lower control arm. This causes the top of the wheel to lean inward as the wheel rises. Any side-to-side movement of the tire that could cause scuffing and result in tire wear is eliminated by the short, long arm design.

If the control arms are of equal length, the wheel will move in an arc as it passes over irregular road surfaces. The short, long arm suspension is designed to allow each wheel to compensate for changes in the road surface while not greatly affecting the opposite wheel.

The upper control arm is attached to a cross shaft through two combination rubber and metal bushings. The cross shaft, in turn, is bolted to the frame. A ball joint, called the upper ball joint, is attached to the outer end of the upper arm and connects to the steering knuckle through a tapered stud held in position with a nut. The inner ends of the lower control arm have pressed-in bushings. Bolts, passing through the bushings, attach the arm to the frame. The lower ball joint is usually pressed into the control arm and connects to the steering knuckle through a tapered stud that is held in position with a nut. A ball joint is used on the control arms because it allows movement in more than one direction. It allows the up-and-down motion required as the wheels pass over dips and bumps. This type of joint also allows side-to-side motion as the wheels are turned back and forth for turns.

The ball stud in the ball joint is a tapered stud at one end with a ball-shaped end. The ball end is supported in a similarly shaped housing called a socket. The shape of the housing allows the ball stud to turn around or move side to side. A plastic or sintered iron bearing is positioned between the ball and socket. The bearing allows the ball stud to turn in relation to the housing for steering. The tapered stud and nut hold the ball joint in position in the steering knuckle.

Grease is used to prevent wear between the ball stud and bearing. A rubber seal is held in position around the ball stud by a seal retainer. The seal holds in the grease and prevents the entrance of dirt or moisture. The steering knuckle assembly is used to mount the wheel and wheel bearing assembly to the control arms. A spindle is usually forged in one piece with the steering knuckle. The wheel spindle is the unit that carries the disc rotor hub and bearing assembly. Through the wheel bearings, it carries the entire wheel load. The wheel bearings have a large inside bearing and a small outer bearing. The disc rotor hub is designed so that the center plane of the wheel is closer to the center plane of the larger inside bearing. The inside bearing supports most of the wheel load.

A coil spring is commonly used on the short, long arm suspension system. The most common spring mounting position is between the frame and the lower control arm. Some cars have the spring mounted from the frame to the upper control arm. In either case, the shock absorber is mounted through the center of the spring. Most short, long arm systems use a stabilizer bar between the two sides of the suspension. The sway bar connects both lower control arms to the frame crossmember. Movements affecting one wheel are partially transmitted to the opposite wheel through the frame to stabilize body roll. The sway bar is attached to the frame crossmember and lower control arms through rubber insulator bushings to reduce noise and vibrations. Sway bar end bushings and crossmember bushings are permanently installed on the sway bar.

MacPherson Strut Front Suspension

The MacPherson strut suspension has become very popular on both imported and American vehicles. The MacPherson strut suspension uses a single lower control arm connected to a long, tubular assembly called a strut. The shock absorber, strut, and spindle are a combined unit that is supported by the coil spring at the upper end and by the lower control arm at the bottom. A ball joint is attached to the lower part of the spindle. The lower control arm is sometimes referred to as a track control arm, or transverse link. The lower arm is held in position by a sway bar and frame-mounted rod called a strut rod, or by a stabilizer bar that functions as a combined strut rod and sway bar.

The shock absorber is called a cartridge and fits inside the strut housing. A metal dust cover is used on some units to protect the strut cartridge assembly. A coil spring is held in place by a lower spring seat welded to the strut housing and an upper spring seat bolted to the shock absorber piston rod. The upper mount is bolted to the vehicle body, through two or three studs that go through the vehicle shock tower or fender well. A rubber bumper fits on the piston rod and protects it in case the shock absorber is compressed to its limit.

Some vehicles use a suspension system described as a modified MacPherson strut. This suspension, shown below has a lower control arm and coil spring similar to that used on the short, long arm suspension. Instead of an upper control arm, a strut assembly connects the top of the steering knuckle to the body. In this case, the strut does not have a spring attached to it. The strut acts as the upper control arm and shock absorber.

Q & A: Front suspension

Question:

1. My mechanic says my car needs ball joints. Please explain.
Answer:

Ball joints are a part of your vehicle's suspension that connects the steering knuckles to the control arms. A ball joint is essentially a flexible ball and socket that allows the suspension to move and at the same time the wheels to steer. Cars and trucks without strut suspensions typically have four of them (one upper and one lower on each side). Cars and minivans with strut suspensions have only two (one lower ball joint on each side). Some front-wheel drive cars also have ball joints on the rear suspension.
Ball joint locations in front end

Like any other suspension component, ball joints eventually wear and become loose. Excessive play in the joint can affect wheel alignment and tire wear. Loose joints can also cause suspension noise (typically a "clunking" sound when hitting a bump).

WARNING: If a ball joint fails, the suspension can collapse causing a loss of control. So don't put off having a bad set of joints replaced.

JOINT INSPECTION

Joints should be inspected before they're greased (since grease takes up some of the slack in the joint). Ball joints are pretty easy to check, but each type requires a different inspection procedure. Use the wrong procedure and you'll get misleading results. The procedure that needs to be used depends on the location and loading of the joint:

* LOWER LOAD CARRYING ball joints are found on front- and rear-wheel drive vehicles where the coil spring or torsion bar is on the lower control arm. You'll also find them on the rear suspension of 1985 & up FWD Buick, Cadillac, Pontiac & Oldsmobiles, too.

Joints with built-in wear indicators (most GM and Ford RWD cars, rear joints on the FWD GM cars, and GM RWD vans, S10 & S15 Blazer) must be checked with the full weight of the vehicle on the tires on the shop floor or on a drive-on style ramp -- not with the wheels up or the suspension supported by jack stands.

No measurements are required if a joint has a wear indicator because internal play is indicated by the position of the grease fitting boss. The boss protrudes about .050 inches on a new joint. As the joint wears, the boss recedes into the housing. The joint is considered "good" as long as you can see or feel the edge of the boss protruding from the housing. But if the top of the boss is flush or below the housing, it's time to replace the joint.

On lower load carrying ball joints without a wear indicator, the joint is checked in the unloaded condition with the wheel raised off the ground and the lower control arm supported by a jack stand. A dial indicator is then used to measure play in one of two directions: sideways (horizontal or radial play) or vertically (axial or up-and-down play). The direction to measure depends on the application (refer to a manual for the exact specs).

Sideways play is measured with the indicator positioned against the inside of the wheel rim near the joint. The wheel should be pushed in and out by hand to check sideways play, and lifted with no more than 25 lbs. of force to check vertical play. Many joints allow up to .250 in. of sideways (radial) play, but some allow no play or only .015 in. of play. Always refer to the vehicle manufacturer's specs.

Vertical play is measured with the dial indicator positioned against the knuckle stud nut (Ford & GM) or the joint housing (Chrysler). A joint that has more than .050 in. of vertical play doesn't necessary require replacement because the specs range from zero play to as much as .125 inch of play.

The most common mistake that's made here is to use too much pressure on a pry bar or to insert a pry bar between the control arm and knuckle rather than under the wheel. Pry hard enough and any joint may appear to be bad.

* LOWER FOLLOWER NONLOADED ball joints are found on two kinds of applications: RWD cars where the spring is over the upper control arm, and vehicles with MacPherson strut suspensions. On both applications the lower joint is checked with the wheel raised off the ground hanging free (no stand under the lower control arm). Rock the wheel in and out by hand. A good joint should show no movement.

One exception here is 1978-80 Omni & Horizon which allows up to .050 inch of sideways play. Another exception is Chrysler FWD minivans and FWD cars ('81 & up). On these applications, the lower joint has a wear indicator grease fitting. Joint play is checked with the wheels on the ground rather than raised. If the grease fitting can be twisted with your fingers, the joint needs to be replaced.

* UPPER LOAD CARRYING ball joints are found on vehicles where the spring or torsion bar is on the upper control arm. Like the lower follower nonloaded ball joints, the upper joints are checked in the unloaded condition with the wheels off the ground -- but with a wedge or block between the frame and upper control arm to support the upper arm. On most applications, any movement calls for replacement. But on some Fords, up to .250 in. of radial play is allowed.

* UPPER FOLLOWER NONLOADED ball joints are also checked with the wheels off the ground but with the lower control arm supported. Any movement usually calls for replacement.

JOINT REPLACEMENT

Any joint that exceeds the vehicle manufacturer's maximum allowable wear needs to be replaced. The greater the amount of wear, the greater the urgency to replace it.

Ball joints are often replaced in complete sets, or at least in matched pairs on both sides (both lowers or both uppers). This is because the joints on both sides of a vehicle usually have the same amount of wear. If one is bad, the other usually is too. Load carrying ball joints usually wear out before ones that don't carry a load, so it may only be necessary to replace the loaded joints instead of the complete set.

Replacing a set of ball joints requires separating the control arms from the steering knuckles, a job which can be difficult depending on the design and age of the vehicle. At the very least, it usually requires a special "ball joint fork" tool to loosen the ball joint stud from the knuckle. If this sounds like more of a a job than you want to tackle, let a professional do it the work.

Question:

2. I feel a high speed shimmy in the steering wheel. What's causing it?
Answer:

A high speed shimmy is usually caused by a wheel that's out of balance or a bent wheel.
The first thing to check for would be a bent wheel. Raise the front of the vehicle off the ground and rotate each wheel by hand. If you see any sideways or in and out movement of the wheel, it is bent and needs to be replaced.

WARNING: Although some people claim they can straighten bent wheels, doing so is risky -- especially with aluminum alloy wheels. Replacement is the safest option (but also expensive).

If you don't see any sideways movement in the wheel, it doesn't necessarily mean the wheel is straight. There may be just enough sideways runout to cause a shimmy, but not enough to see. To find this kind of problem, you'll need a dial indicator. More than about .050 inch of sideways runout can be enough to cause a problem.

If the wheels seem to be straight, have the balance of both wheels checked (or rebalanced). If that fails to cure the shimmy, you may have some kind of tire problem due to defective belt alignment or tire construction. Other causes may include loose or improperly adjusted wheel bearings, insufficient caster alignment (check and readjust alignment as needed), or a worn steering damper (on trucks or other vehicles equipped with a steering stabilizer).