Parking Control Valve Operational Check Operational Check

1. Block the wheels.
2. Start the engine and charge the system to the air compressor governor cut-out point.
3. Stop the engine.



4. Push in the trailer air supply knob.

If the trailer air supply knob does not remain in, overhaul or replace the parking control valve.

Important: The park control valve must not pop out before the trailer air supply knob. If the park control valve knob pops out first, overhaul or replace the parking control valve.

5. Slowly reduce the pressure in the air reservoirs.

The trailer air supply knob must pop out when the air pressure is reduced to approximately 241-310 kPa (35-45 psi).

6. Hold in the trailer air supply knob and continue to reduce the pressure in all of the air reservoirs.

Air must start to escape from the exhaust port when the trailer air supply line pressure reaches 138-241 kPa (20-35 psi).

7. Release the trailer air supply knob.
8. Start the engine.
9. Charge the system to the air compressor governor cut-out point.
10. Stop the engine.
11. Push in the control valve knob.

If the park control valve does not remain in, overhaul or replace the parking control valve.

12. Pull out the trailer air supply knob.
13. Reduce the air pressure in all reservoirs. The park brake control knob must pop out at 138-209 kPa (20-30 psi). If the park control knob does not pop out at the specified pressure, overhaul or replace the parking control valve.
14. Start the engine.
15. Charge the system to the air compressor governor cut-out point.
16. Stop the engine.
17. Pull out the trailer air supply knob.

If the park control knob does not remain in , overhaul or replace the parking control valve.

18. Push in the trailer supply knob.
19. Pull out the park control knob. The trailer air supply knob must pop out almost instantaneously. If the trailer air supply knob does not pop out as specified, overhaul or replace the parking control valve.
20. Remove the wheel blocks.

Parking Control Valve Operational Check Leakage Test

1. Block the wheels.
2. Start the engine.
3. Charge the system to the air compressor governor cut-out point.
4. Stop the engine.
5. Inspect for air leakage between the valve body and cover plate. Air leakage at the exhaust port must not exceed a 25.4 mm (1 in) bubble in 5 seconds.

If air leakage is excessive, overhaul or replace the parking control valve.

6. Push in the trailer air supply knob.
7. Inspect the exhaust port for air leakage. Air leakage at the exhaust port must not exceed a 25.4 mm (1 in) bubble in 5 seconds.

If air leakage is excessive, overhaul or replace the parking control valve.

8. Start the engine.
9. Charge the system to the air compressor governor cut-out point.
10. Stop the engine.
11. Push in the park control knob.
12. Inspect the exhaust port for air leakage. Air leakage at the exhaust port must not exceed a 25.4 mm (1 in) bubble in 5 seconds.

If air leakage is excessive, overhaul or replace the parking control valve.

13. Remove the wheel blocks.