GM Service Manual Online
For 1990-2009 cars only
Makes 🢒 GMC_Truck 🢒 2003 🢒 TopKick C-Series Commercial (Cutaway) C4/C5 🢒 Brakes 🢒 Air Brakes 🢒 Trailer Brake Supply Valve Leakage Test
  1. Block the wheels.
  2. Start the engine.
  3. Charge the system air pressure to the governor cut-out point.

    4. Object Number: 209561 Size: SH
  4. Pull out the trailer air supply knob (3).

    5. Object Number: 209563 Size: SH
  5. Pull out the system park knob (1).

    6. Object Number: 209561 Size: SH
  6. Apply a soap solution to the exhaust vent and around the base of the trailer air supply knob (3).
  7. Verify that leakage is less than a 25 mm (1 in) bubble in 5 seconds. If not, replace the valve. Refer to Trailer Brake Supply Valve Replacement or overhaul the valve. Refer to Air Brake System Description and Operation .
  8. If the leakage exceeds these limitations, replace the valve. Refer to Trailer Brake Supply Valve Replacement or overhaul the valve. Refer to Air Brake System Description and Operation .
  9. Push in the trailer air supply knob (3).

    10. Object Number: 209563 Size: SH
  10. Apply a soap solution to the exhaust port.
  11. Check that the leakage is less than a 25 mm (1 in) bubble in 5 seconds.
  12. If the leakage exceeds these limitations, replace the valve. Refer to Trailer Brake Supply Valve Replacement or overhaul the valve. Refer to Air Brake System Description and Operation .
  13. Set the parking brake.
  14. Remove the wheel blocks.