- Block the wheels.
 
- Apply the parking brake.
 
- Start the engine.
 
- Charge the system air pressure to the governor cut-out point.
 
- Check that the service brakes fully apply when depressing the
brake pedal.
 
- Check that the brakes promptly release
when the brake pedal is released. If the brakes are sluggish, check that air
vents through the exhaust port (5) when releasing the brakes.
 
-  If the brakes do not promptly release, replace or overhaul the
valve (4). Refer to 
Air Brake Quick Release Valve Replacement 
 or 
Air Brake System Description and Operation 
.
 
- Remove the wheel blocks.