- Block the wheels.
 
- Start the engine.
 
- Charge the system air pressure to the governor cut-out point.
 
- Have an assistant apply the brakes hard and then release them
several times.
 
- Check that the brakes apply and release
promptly at each wheel.
 
- Replace or overhaul the valve (5) if the brakes do not
 release promptly. Refer to 
Rear Air Brake Relay Valve Replacement 
 or 
Air Brake System Description and Operation 
.
 
- Remove the wheel blocks.