GM Service Manual Online
For 1990-2009 cars only

Hard Pedal

Checks

Action

Inspect for the following conditions:

    â€¢ Broken or damaged hydraulic pipes or hoses
    â€¢ A damaged or loose vacuum hose
    â€¢ A collapsed vacuum hose

Replace any faulty pipes or hoses.

Inspect for a plugged or loose vacuum fitting.

Clean and correctly tighten the vacuum fitting.

Inspect for the following conditions:

    â€¢ A faulty vacuum check valve or grommet
    â€¢ Faulty air valve seal or support plate
    â€¢ Damaged floating control valve
    â€¢ Bad stud welds on the front or rear housing or power head
    â€¢ Faulty booster diaphragm
    â€¢ Worn or distorted reaction plate or levers
    â€¢ Cracked or broken power pistons or retainer

Replace the vacuum booster

Grabby Brakes

Checks

Action

DEFINITION: Apparent Off-On Condition

Inspect for broken or damaged hydraulic brake pipes and hoses.

Replace any faulty pipes or hoses.

Inspect the master cylinder for a low fluid level.

    â€¢ Fill reservoirs with the proper brake fluid.
    â€¢ Check for leaks.

Inspect the master cylinder for faulty seals.

Repair or replace any faulty seals.

Inspect the master cylinder for a cracked casing.

Replace the master cylinder.

Inspect the following components for leaks:

    â€¢ Front calipers
    â€¢ Rear wheel cylinders
    â€¢ Pipes
    â€¢ Connections

Repair or replace any faulty components.

Check the hydraulic system for air.

Bleed the system.

Brakes Fail to Release

Checks

Action

Inspect for the following conditions:

    â€¢ A blocked passage in the power piston
    â€¢ An air valve sticking shut
    â€¢ A broken piston return spring or air valve spring

Replace the vacuum booster.

Inspect for a tight brake pedal linkage.

Repair or replace any faulty component.

Inspect for misadjusted stoplamp or cruise control switches.

Correctly adjust the switches.