Air Dryer/Moisture Ejector System Check for GMC Truck TopKick C-Series (Crew) C6/C7/C8 2004

1. Start the engine.
2. Charge the system air pressure to the governor cut-out point.
3. Have an assistant apply and release the brake pedal several times.



4. Check that a spurt of air occurs at the exhaust port.
5. Clean or replace the purge valve (1) if there is no air at the exhaust port.