For 1990-2009 cars

1. Charge the air system to full pressure.
2. Turn off the engine.
3. Apply a soap solution around the cap of the valve (4).
4. Check for soap bubbles indicating leads. A one inch bubble in three seconds or longer is acceptable.
5. Drain the air pressure from the delivery port and remove the air line connected to the port.
6. Apply a soapy solution around the delivery port. A one inch bubble in five seconds or more is acceptable.
7. If excessive leakage is present, replace or overhaul the valve (4). Refer to Pressure Protection Valve Replacement or Air Brake System Description and Operation .