Component Tests General Information

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. Failure to follow these instructions may result in personal injury.

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 DOT 3 motor vehicle brake fluid.

Brake Booster
1. With the transmission in NEUTRAL and the engine stopped, apply the brakes several times to exhaust the vacuum in the vacuum boost system or the pressure in the Hydro-Boost system.
2. Hold the brake pedal in the applied position.
3. Start the engine.
4. If the power brake system is functioning correctly, the brake pedal can be felt to move downward after the engine starts.
5. With a vacuum type power brake booster, if engine vacuum is available to the power brake booster and no power assist is felt, replace the power brake booster and retest the system.
If power steering pump pressure is available to the Hydro-Boost~ power brake booster and no power assist is felt, replace the Hydro-Boost~ power brake booster and retest the system.
If power steering pump pressure is not available at the Hydro-Boost~ power brake booster, check the power steering pump pressure and flow.
On a Hydro-Max booster system, if power is available at the electric pump and no power assist is felt, replace the Hydro-Max booster assembly and retest the system.
If power is not available at the electric pump, correct the electrical concern and retest the system.

Accumulator, Hydro-Boost(R) Only
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, replace the Hydro-Boost(R) power brake booster and retest the system.

Check Valve-Vacuum Booster Only
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 one more power-assisted brake operation.
^ Replace the power brake booster check valve if it fails the above test.

Brake Master Cylinder
1. Disconnect the brake lines 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 must be replaced.

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 lines 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.