Check if the brakes are out of adjustment.

Refer to Air Drum Brake Adjustment .

Blockage in air lines preventing air chamber from exhausting

Replace lines and fittings as needed to remove contamination or blockage.

Air valves sticking

Repair or replace the valve as necessary.

Air chamber not set properly:

1. Too much rod free-travel
2. Air chamber in wrong position in bracket slot
3. Pushrod length too long

1. Adjust the brakes.
2. Reposition the air chamber.
3. Adjust the clevis or shorten the pushrod.

Incomplete release of park brake after application of air to the chamber:

1. Internal cup/cone hang up
2. Damaged pushrod
3. Diaphragm leak in parking chamber
4. Cocked power spring

1. Repair or replace the cup/cone.
2. Replace the pushrod.
3. Replace the diaphragm or air chamber.
4. Repair the power spring.

Slack adjuster not set properly

Refer to Air Drum Brake Adjustment .

Drum out-of-round

Repair or replace drums as necessary.

Check for brake pedal linkage binding.

Refer to Air Brake Pedal Replacement .

Check for brake shoe binding.

Refer to Parking Brake Shoe Inspection .

Check for camshaft bushing binding.

Refer to Air Drum Brake Adjustment .