Trailer Brake Control Valve Leakage Test for GMC Truck TopKick C-Series (Conventional) C6/C7/C8 2003

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. Push down the trailer air brake control valve lever to the full off position.
6. Inspect the valve body and the exhaust port for any air leakage.

If any air leakage is present, replace or overhaul the trailer air brake control valve. Refer to Trailer Brake Control Valve Replacement or Air Brake System Description and Operation .

7. Pull up the trailer air brake control lever to the full on position.
8. Inspect the valve body and the exhaust port for any air leakage.

If any air leakage is present, replace or overhaul the trailer air brake control valve. Refer to Trailer Brake Control Valve Replacement or Air Brake System Description and Operation .

9. Remove the wheel blocks.