GM Service Manual Online
For 1990-2009 cars only
  1. Block the wheels.
  2. Start the engine.
  3. Charge the system air pressure to the governor cut-out point.
  4. Release the brake pedal.
  5. Coat the exhaust port and the area around the exhaust port (retaining ring) with a soap solution.

  6. Object Number: 202648  Size: SH
  7. Check that the leakage is less than a 25 mm (1 in) bubble in 3 seconds.
  8. Repair or replace the valve (5) if the leakage exceeds these limitations.
  9. Firmly apply the brake pedal.
  10. Coat the exhaust port with a soap solution.
  11. Check that leakage is less than a 25 mm (1 in) bubble in 3 seconds.
  12. Coat the outside of the valve where the cover joins the body with a soap solution.
  13. Leakage is not permissible.
  14. Replace the valve (5) if any bubbles appear.
  15. Remove the wheel blocks.