Front Air Brake Limit Valve Leakage Test for GMC Truck TopKick C-Series (Conventional) C4/C5 2005

1. Block the wheels.
2. Apply the parking brake.
3. Start the engine.
4. Charge the system air pressure to the governor cut-out point.
5. Have an assistant apply the brake pedal.
6. Apply a soap solution to the exhaust port and around the seam between the cover and the body.



7. Check that no bubbles appear around the seam.
8. Replace or overhaul the valve (4) if bubbles appear. Refer to Front Air Brake Limit Valve Replacement or Air Brake System Description and Operation .
9. Check that the exhaust port leakage is less than a 25 mm (1 in) bubble in 5 seconds.
10. Replace or overhaul the valve (4) if the leakage exceeds this amount. Refer to Front Air Brake Limit Valve Replacement or Air Brake System Description and Operation .
11. Remove the wheel blocks.