Component Tests

Component Tests

WARNING: Use of other than the approved DOT 3 brake fluid will cause permanent damage to the brake components and will render the brakes inoperative.

NOTE: If a vehicle with a locked wheel must be moved, loosen the bleeder screw to relieve pressure.

Always check brake fluid level and, if necessary, fill with clean, specified brake fluid.

Brake Booster
1. With the engine OFF, apply the brake pedal several times to deplete the power assist reserve in the brake booster.
2. Hold the brake pedal in the applied position.
3. Start the engine.
4. The brake pedal should drop slightly after the engine starts.
5. On vacuum brake booster equipped vehicles, if the brake pedal does not drop after the engine is started, check for vacuum at the brake booster.
^ With the engine OFF, disconnect the vacuum hose and check valve at the brake booster.
^ Vacuum should be heard escaping from the brake booster.
6. If vacuum is not available at the brake booster, check for vacuum at the source and check the vacuum hose for leaks.
^ On vehicles without a vacuum pump, check for vacuum at the engine.
^ On vacuum pump equipped vehicles, inspect the accessory drive and accessory drive belt. Refer to Drive Belts, Mounts, Brackets and Accessories.
7. If vacuum is available at the brake booster and no power assist is felt, install a new brake booster and retest the system.
8. On Hydro-Boost(R) equipped vehicles, if the brake pedal does not drop after the engine is started, check the power steering pump pressure and flow.
9. If power steering pump pressure is available to the Hydro-Boost(R) and no power assist is felt, install a new Hydro-Boost(R) brake booster and retest the system.

Accumulator
1. Start and run the engine.
2. Stop the engine.
3. Apply the brakes. The accumulator in the Hydro-Boost(R) power brake booster should retain enough pressure for at least 2 power-assisted brake operations. If no power assist is felt, install a new Hydro-Boost(R) power brake booster and retest the system.

Check Valve
The function of the power brake booster check valve is to allow manifold vacuum to enter the power brake booster and prevent the escape of vacuum in case manifold vacuum is lost during sustained full throttle operation.

To test the function of the power brake booster check valve:
^ Start and run the engine for at least 10 seconds.
^ Operate the brake pedal to check for power assist.
^ Disconnect the vacuum booster hose from the power brake booster. Do not remove the power brake booster check valve from the power brake booster.
^ There should be enough vacuum retained in the power brake booster for at least 1 more power-assisted brake operation.

Brake Master Cylinder
1. Disconnect the brake tubes at the brake master cylinder.
2. Plug the outlet ports of the brake master cylinder.
3. Apply the brakes. If brake pedal height cannot be maintained, the brake master cylinder has an internal leak and a new one must be installed.

Compensator Port Check
The purpose of the compensator ports in the brake master cylinder is to supply any additional brake fluid required by the system due to brake pad wear, and to allow brake fluid returning from the brake hoses and tubes to the brake master cylinder to enter the brake master cylinder reservoir.

The returning brake fluid will cause a slight turbulence in the brake master cylinder reservoir. Turbulence seen in the brake master cylinder reservoir upon release of the brake pedal is normal and shows that the compensating ports are not plugged.