1994 Chevrolet P30 VAN Brake Service (ONLINE REPAIR MANUALS)

In order to properly service power brake systems, a thorough understanding of the various power assist systems is necessary. These systems provide a mechanical assist, acting to increase the force applied to the master cylinder piston by the driver while decreasing the effort necessary to obtain acceptable stopping performance. Two basic types of power assist mechanisms are used: vacuum assist diaphragm assemblies which use engine vacuum and in some cases vacuum from an external vacuum pump, and hydraulic assist assemblies which use hydraulic pressure developed by an external pump (...

Accessing Diagnostic Trouble Codes

1992

Diagnostic trouble codes can be accessed by connecting a TECH 1 or equivalent scan tool or by manually grounding the Assembly Line Diagnostic Link (ALDL) connector. To manually ground the ALDL connector, connect a jumper wire between terminals A and H, Fig. , and observe the flashes of the brake warning lamp. Note the following when performing the Diagnostic Circuit Check to access diagnostic trouble codes:

• When terminals are jumped, count number of short flashes starting from initial long flash, include long flash in count.
• The count se...

Certain general service procedures apply, regardless of whether the brakes are vacuum or hydraulically assisted. Only top quality, clean brake fluid should be used. More seals and valves are used with power brake systems than with ordinary brakes, so an inferior brake fluid will do much more damage. For the same reason, be sure all dirt is kept out of the system. Additionally, care must be taken not to mix the fluids of the booster hydraulic system and brake hydraulic system as the fluids are not compatible.

If the power unit fails, the brakes will still operate, as the conventio...

When working on or around brake assemblies, care must be taken to prevent breathing asbestos dust, as many manufacturers incorporate asbestos fibers in the production of brake linings. During routine service operations, the amount of asbestos dust from brake lining wear is at a low level due to a chemical breakdown during use, and a few precautions will minimize exposure. Do not sand or grind brake linings unless suitable local exhaust ventilation equipment is used to prevent exces...

• Inspect components for damage or unusual wear. Replace as necessary.
• Inspect backing plate attaching bolts, and ensure they are tight.
• Inspect wheel cylinders. Excessive fluid indicates cup leakage and need for wheel cylinder replacement. A slight amount of fluid is always present and is considered normal, act...

Brake System Bleed

1992

Before bleeding the brakes, the front and rear displacement cylinder pistons must be returned to the top most position. Using a TECH 1 or equivalent scan tool, enter manual control function and apply the front and rear motors. Ensure enable relay is on.

Use only DOT 3 brake fluid from a clean and sealed container. Do not use DOT 5 brake fluid.

Pressure Bleeding

• Remove master cylinder cover, ensure reservoir is properly filled.
• Connect bleeder adapter tool No. J 35589, or equivalent, to master cylinder reservoir.
• Connect bleeder adapter to pressure bleeding equipm...