Power Brake Check Valve

New power brake check valve. The check valve keeps the vacuum in the booster from leaking back into the intake when engine vacuum drops because of high loads or when the engine dies. The symptoms would be no power boost when you turn the engine off or when the engine dies. Step on the brake with the engine running and note pedal position. Turn off engine and step again and the position should be the same. If the pedal is hard and higher then the check valve or booster is bad.