1993 Chevrolet P30 VAN Brake Service (ONLINE REPAIR MANUALS)

In order to properly service power brake systems, a thorough understanding of the power assist system 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.

Hydraulic assist units incorporate a basic open center spool valve, hydraulic cylinder and an accumulator assembly in a common housing. When the brake pedal is depressed, the hydraulic piston moves forward closing off fluid relief passages, the spool valve applies flui...

Delco-Moraine Master Cylinder

Composite Type

When performing the following procedures, refer to Fig. for all models except Lumina APV, Silhouette & Trans Sport, noting that the composite reservoir may vary in design. Refer to Fig. for Lumina APV, Silhouette & Trans Sport models.

Disassemble

• Remove master cylinder from vehicle.
• Remove reservoir cover and diaphragm. Discard old brake fluid in reservoir.
• Inspect cover and diaphragm. Replace if cut, cracked or deformed.
• Remove fluid level switch and proportioning valve assembly, if equipped.
• Depress primary piston and remove lock ring.
• P...

General Service Precautions

Avoid contact with brake fluid when servicing the anti-lock brake syste...

2WD Models

• Raise and support vehicle.
• Remove tire and wheel assembly.
• Remove caliper as outlined under "Caliper Service."
• Remove grease cap from hub/rotor.
• Remove cotter pin, nut and washer.
• Remove hub/rotor from spindle, being careful not to damage spindle threads or outer bearing.
• Reverse procedure to install, noting the following:
• Apply high-temperature wheel bearing grease to inner and outer wheel bearings.
• Torque nut to 12 ft. lbs. while turning wheel assembly forward by hand, back...

Removal

• Siphon ^2/3 of brake fluid from master cylinder reservoir serving front disc brakes.
• Raise vehicle, support on jack stands and remove front wheels.
• Bottom caliper piston in bore. Insert a screwdriver between inboard shoe and piston, then pry piston back into bore. The piston can also be bottomed in the bore with a large C-clamp, Fig. .
• Remove support key retaining screw.
• Drive caliper support key and spring from steering knuckle with a suitable drift and hammer, Fig. .
• Lift caliper from anchor plate and off rotor, Fig. . Hang caliper from coil spring with wire. Do not allow cal...

Brake Drums

Any time the brake drums are removed for brake service, the braking surface diameter should be checked with a suitable brake drum micrometer at several points to determine if they are within the safe, oversize limit stamped on the brake drum outer surface. If the braking surface diameter exceeds specifications, the drum must be replaced. If the braking surface diameter is within specifications, drums should be cleaned and inspected for cracks, scores, deep grooves, taper, out-of-roundness and heat spotting. If drums are cracked or heat spotted, they must be ...