Check Valve

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 one more power assisted brake operation.

Brake Master Cylinder Bypass Condition Test
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 rebuilt or 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.