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Throughout this group, references may be made to a particular vehicle by letter or number designation. A chart showing the break down of these designations is included in the Introduction Section at the front of this service manual.

Standard brake equipment consists of:

²Double pin floating caliper disc front brakes.

²Rear automatic adjusting drum brakes.

²Differential valve with a brake warning switch.

²Master cylinder.

²Vacuum power booster.

²Double pin floating caliper rear disc brakes are available on some models.

The Anti-Lock braking system. Uses the standard power brake system caliper assemblies, braking discs, pedal assembly, brake lines and hoses. The unique parts of the Anti-Lock braking system consists of the following components. Unique proportioning valves, wheel speed sensors, tone wheels, electronic control units, modulator assembly and hydraulic assembly which replaces the conventional master cylinder and power booster. These components will be described in detail in the Anti-Lock brake section in this group of the service manual.

The front disc brake shoes have semi-metallic linings.

The hydraulic brake system (Figs. 1, 2 and 3) is diagonally split on both the Non-ABS and ABS braking system. With the left front and right rear brakes on one hydraulic system and the right front and left rear on the other.

The Non-ABS and ABS brake system uses different types of brake line fittings and tubing flares. The Non-ABS brake system uses double wall tubing flares and fittings at all tubing joint locations. The ABS brake system uses both ISO style tubing flares and double wall tubing flares and corresponding fittings at different joint locations. See (Figs. 2 and 3) for specific joint locations and type of tubing flare.

The front disc brakes consist of two different types of caliper assemblies. The double pin Kelsey-Hayes caliper (family caliper) with a bolt-on adapter attached to the steering knuckle, or a double pin Kelsey-Hayes caliper which mounts directly to rails on the steering knuckle. The non-family caliper.

CAUTION: Caliper pistons, boots and seals for the different caliper assemblies used on the front and rear disc brake assemblies are not interchangeable. Misusage could result in a complete brake system failure. Be sure that the parts are replaced with the correct replacement parts, refer to the parts book for the type and model year of the vehicle being worked on.

The master cylinder is anodized, lightweight aluminum, with a bore size of 24.0mm, 21.0mm or 7/8 inch.

MASTER CYLINDER FLUID LEVEL

NON-ABS BRAKES

Check master cylinder reservoir brake fluid level a minimum of twice a year.

Master cylinder reservoirs are marked with the words fill to bottom of rings indicating proper fluid level (Fig. 1).

If necessary, add fluid to bring the level to the bottom of the primary reservoir split ring.

Use only Mopart brake fluid or an equivalent from a sealed container. Brake fluid must conform to DOT 3, specifications.

DO NOT use brake fluid with a lower boiling point, as brake failure could result during prolonged hard braking.

Use only brake fluid that was stored in a tightlysealed container.

DO NOT use petroleum-based fluid because seal damage in the brake system will result.

Fig. 1 Master Cylinder Fluid Level (Non-ABS)

ABS BRAKES

The hydraulic assembly is equipped with a plastic fluid reservoir with a filter/strainer in the filler neck of the reservoir.

The Anti-Lock brake system requires that the hydraulic accumulator be de-pressurized whenever checking the brake fluid level. To check the brake fluid level, the following procedure should be used:

(1)With the ignition off, de-pressurize the hydraulic accumulator by applying the brake pedal approximately 40 times, using a pedal force of approximately 220 N (50 lbs.). A noticeable change in pedal feel will occur when the accumulator is de-pressurized. Continue to apply the pedal several times after this change in pedal feel occurs to insure that the brake system is fully de-pressurized.

(2)Thoroughly clean both reservoir caps and surrounding area of reservoir, (Fig. 2) before removing caps. This is to avoid getting dirt into the reservoir and contaminating the brake fluid.

(3)Inspect the brake fluid to see if it is at the proper level, see instructions on top of reservoir. (FILL TO TOP OF WHITE SCREEN ON FRONT FILTER/STRAINER.)

(4)Fill reservoir with brake fluid to top of screen (Fig. 3) on the filter/strainer located in brake fluid reservoir. Only use brake fluid conforming to DOT 3 specifications such as Mopart or equivalent.

(5)Replace brake fluid reservoir caps.

ADJUSTING REAR SERVICE BRAKES

Normally, self adjusting drum brakes will not require manual brake shoe adjustment. Although in the event of a brake reline it is advisable to make the initial adjustment manually to speed up the adjusting time.

(1)Raise the vehicle so all wheels are free to turn. See Hoisting Recommendations in the Lubrication And Maintenance Section, at the front of this service manual.

(2)Remove rear brake adjusting hole rubber plug (Fig. 4), from the rear brake shoe support plate.

(3)Be sure parking brake lever is fully released. Then back off parking brake cable adjustment so there is slack in the cable.

(4)Insert Brake Adjuster, Special Tool C-3784, (Fig.

5)or equivalent through the adjusting hole in support plate and against star wheel of adjusting screw. Move handle of tool upward until a slight drag is felt when the road wheel is rotated.

(5)Insert a thin screwdriver or piece of welding rod into brake adjusting hole (Fig. 5). Push adjusting lever out of engagement with star wheel. Care should be taken so as not to bend adjusting le-

Fig. 3 ABS Reservoir Fill Level On Filter/Strainer

ver or distort lever spring. While holding adjusting lever out of engagement with star wheel, back off star wheel to ensure a free wheel with no brake shoe drag.

(6)Repeat above adjustment at the other rear wheel. Install adjusting hole rubber plugs (Fig. 4) in rear brake supports.

(7)Adjust parking brake after wheel brake adjustment. See parking brake adjustment, under Parking Brakes in this group of the service manual.

Fig. 4 Brake Adjusting Hole Plug

It is important to follow the above sequence to avoid the possibility of the parking brake system causing brake drag. This could occur if the parking brakes are adjusted before the service brakes.

TESTING APPLICATION ADJUSTER OPERATION

Place the vehicle on a hoist with a helper in the driver's seat to apply the brakes. Remove the access plug from the rear adjustment slot in each brake

Fig. 5 Brake Drum Adjustment With Tool C-3784

support plate (Fig. 4) to provide access to the adjuster star wheel. Then, to eliminate the possibility of maximum adjustment, where the adjuster does not operate because the closest possible adjustment has been reached. Back the star wheel off approximately 30 notches. It will be necessary to hold the adjuster lever away from the star wheel to permit this adjustment.

Spin the wheel and brake drum in the reverse direction, and with a greater than normal force apply the brakes suddenly. This sudden application of force will cause the secondary brake shoe to leave the anchor. The wrap up effect will move the secondary shoe, and the cable will pull the adjuster lever up. Upon application of the brake pedal, the lever should move upward, turning the star wheel. Thus, a definite rotation of the adjuster star wheel can be observed if the automatic adjuster is working properly. If one or more adjusters do not function properly, the respective drum must be removed for adjuster servicing.

BLEEDING BRAKE SYSTEM

CAUTION: For bleeding of the Anti-Lock brake hydraulic system. See the Anti-Lock Brake system service procedures in this group which refers to the particular Anti-Lock brake system being serviced.

PRESSURE BLEEDING

Before removing the master cylinder cover, wipe it clean to prevent dirt and other foreign matter from dropping into the master cylinder.

CAUTION: Use bleeder tank Special Tool C-3496-B with adapter Special Tool C-4578 to pressurize the system for bleeding.

Follow pressure bleeder manufacturer's instructions, for use of pressure bleeding equipment.

When bleeding the brake system. Some air may be trapped in the brake lines or valves far upstream. As much as ten feet from the bleeder screw (Fig. 6). Therefore, it is essential to have a fast flow of a large volume of brake fluid when bleeding the brakes to ensure all the air gets out.

Fig. 6 Trapped Air in Brake Line

To bleed the brake system. Attach a clear plastic hose to the bleeder screw at one wheel and feed the hose into a clear jar containing fresh brake fluid (Fig. 7).

Fig. 7 Proper Method for Purging Air From Brake System (Typical)

Next, open the bleeder screw at least one full turn or more to obtain an adequate flow of brake fluid (Fig. 8).

CAUTION: Just cracking the bleeder screw often restricts fluid flow, and a slow, weak fluid discharge will NOT get all the air out.

After 4 to 8 ounces of fluid has been bled through the brake system. And an air-free flow is maintained in the clear plastic hose and jar, this will indicate a good bleed.