For 1990-2009 cars

1. Block the wheels.
2. Apply the parking brake.
3. Start the engine.
4. Charge the system air pressure to the governor cut-out point.
5. Have an assistant apply the brake pedal.
6. Coat the exhaust port (5) with a soap solution.
7. Check that leakage is less than a 25 mm (1 in) bubble in three seconds.
8. Replace or overhaul the valve (1) if the leakage exceeds these specifications. Refer to Air Brake Quick Release Valve Replacement or Air Brake System Description and Operation .
9. Coat the cover and the mating area between the top and the bottom of the valve (4) with a soap solution.
10. Check for leakage.
11. If any bubbles appear, replace or overhaul the valve (4). Refer to Air Brake Quick Release Valve Replacement or Air Brake System Description and Operation .
12. Remove the wheel blocks.