- Block the wheels.
 
- Remove the valve.
 
- Plug the delivery port.
 
- Connect an air supply to one of the supply ports. Apply approximately
 861 kPa (125 psi) of air pressure.
 
- Apply a soap solution to the opposite supply port.
 
- Check that the leakage is less than a 25 mm (1 in) bubble
 in 5 seconds.
 
- If the leakage exceeds these specifications, replace or overhaul the
 valve. Refer to 
Air Brake Double Check Valve Replacement
 or 
Air Brake System Description and Operation
 .
 
- Disconnect the air supply.
 
- Repeat steps 4 through 6 on the other supply port.
 
- Shut off and disconnect the air supply.
 
- Unplug the delivery port.
 
- Install the valve.
 
- Charge the air supply.
 
- Check the brakes.
 
- Remove the wheel blocks.