Front air brake chambers must be free to breathe through the pushrod opening and the 4 holes near the clamping flange.

Leakage Test

1. Block the wheels.
2. Start the engine.
3. Charge the air system to the air compressor governor valve cut-out point.
4. Stop the engine.
5. Have an assistant apply and hold the brake pedal.
6. Apply a soap solution around the front air brake chamber clamp and the breather holes.
7. Verify that no bubbles appear.

•	Lightly tap on the clamp and tighten the clamp bolts if bubbles appear.

•	Overhaul or replace the front air brake chamber if the bubbles continue. Refer to Front Air Brake Chamber Overhaul .

8. Set the parking brake.
9. Remove the wheel blocks.

Rear air brake chambers must be free to breathe through the pushrod opening and 4 equally spaced holes near the clamping flange. Make sure these openings are clear.

Leakage Test

1. Block the wheels.
2. Start the engine.
3. Charge the air system to the air compressor governor valve cut-out point.
4. Stop the engine.
5. Have an assistant apply and hold the brake pedal.
6. Apply a soap solution around the air brake chamber clamp and the breather holes.
7. Verify that no bubbles appear.

•	Lightly tap on the clamp and tighten the clamp bolts if bubbles appear.

•	Overhaul or replace the rear air brake chamber if the bubbles continue. Refer to Rear Air Brake Chamber Overhaul .

8. Set the parking brake.
9. Remove the wheel blocks.