Vacuum Brake Booster Check Valve: Testing and Inspection
CHECK VALVENOTE: The check valve is pressed into the vacuum hose. The arrow on the hose indicates the direction of hose installation (toward booster).
1. Remove the clamps and remove the hose (with the internal check valve).
2. Apply a suction and pressure to the hose from the engine side. Verify that air flows only toward the engine. If the air passes in both directions or not at all, replace the vacuum hose (along with the check valve).