Vacuum Brake Booster Check Valve: Specifications

Check Valve
The function of the check valve is to allow manifold vacuum to enter the brake booster and prevent the escape of vacuum in case manifold vacuum is lost during sustained full throttle operation. The check valve is located inside the aspirator in the brake booster vacuum hose.
To test the function of the 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 engine port.
^ There should be enough vacuum retained in brake booster for at least one more power-assisted brake operation.