Pressure Protection Valve Operational Check Operational Check

1. Block the wheels.
2. Apply the parking brake.
3. Drain all of the air reservoirs. Refer to Draining Reservoirs .



4. Disconnect the air line from the pressure protection valve supply and the delivery ports.
5. Install test gauges and the drain valves onto the supply and delivery ports.
6. Start the engine.
7. Charge the system to the air compressor governor cut-out point.
8. Stop the engine.
9. While watching the test gauges, slowly exhaust pressure from the delivery side.

•	Both gauges will show a pressure loss until the pressure protection valve reaches its closing pressure.

•	The valve should close within 34 kPa (5 psi) of the rated pressure. If not replace the pressure protection valve.

10. Drain all of the air reservoirs.
11. Remove the drain valve and the test gauges.
12. Install the air lines.
13. Start the engine.
14. Charge the system to the air compressor governor cut-out point.
15. Stop the engine.
16. Inspect the system for air leakage.
17. Test the brakes for proper brake operation.
18. Remove the wheel blocks.

Pressure Protection 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 the pressure protection valve for air leakage. A 25.4 mm (1 in) bubble in 3 seconds or longer is acceptable.

If air leakage is excessive, replace the pressure protection valve.

6. Drain the air pressure from the delivery port and remove the air line connected to it.
7. Inspect the delivery port for leakage. A 25.4 mm (1 in) bubble in 5 seconds or longer is acceptable.

If air leakage is excessive, replace the pressure protection valve.

8. Install the air line.
9. Remove the wheel blocks.