- Block the wheels.
 
- Start the engine.
 
- Charge the system air pressure to the governor cut-out point.
 
- Pull out the system park knob and release the brake pedal.
 
- Apply a soap solution to the exhaust port.
 
- Check the exhaust port for leakage. Slight leakage is permissible.
 
-  If leakage is excessive. 
 
-  Replace the valve. Refer to 
Instrument Panel Mounted Air Brake Park Control Valve Replacement 
 .
 
- Push in the system park knob .
 
- Remove the wheel blocks.