Check Valve

A check valve should be inspected whenever the hose is disconnected or whenever check valve failure is suspected. (An AIR pump that had become inoperative and had shown indications of having exhaust gases in the outlet port would indicate check valve failure.)
1. Remove the check valve from the vehicle.
2. Install a vacuum pump to the nipple side (AIR pump side) of the check valve.
3. Pump the vacuum pump to 10 inches Hg. and observe the gauge.
4. If the vacuum bleeds down to zero within 5 seconds, replace the check valve.