S912-518-103-7 | Genuine Paccar® Air Brake Compressor

1. Generate Compressed Air

• The compressor pulls in atmospheric air and compresses it to high pressure.

• This air is stored in air tanks for immediate use by the brake system.

2. Maintain Air Pressure

• Keeps the brake system pressurized at all times.

• Ensures the brakes are ready whenever the driver presses the pedal.

3. Operate Air Brake Components

• Powers brake chambers that push the brake shoes/pads against the wheels.

• Operates auxiliary systems in some trucks, like suspension or air horns.

4. Ensure Safety in Heavy Vehicles

• Air brakes require a lot of force to stop large vehicles.

• The compressor makes it possible to apply sufficient braking force safely.

• Air tanks take much longer to reach normal operating pressure.

• Brakes may feel weak or delayed.

Indicates the compressor isn’t pumping enough air.

2. Loud or Unusual Noises

• Knocking, rattling, or screeching from the compressor.

• Could indicate worn internal components, loose mounting, or damaged valves.

3. Oil Leaks

• Air compressors on heavy-duty vehicles are often oil-lubricated.

• Oil leaks around the compressor or into the air tanks signal worn seals or damaged internal parts.

4. Excessive Heat

• Compressor gets unusually hot during operation.

• Could be caused by internal friction, lack of lubrication, or air restriction.

5. Air System Warning Lights

• Low air pressure warning or brake system warning lights illuminate on the dashboard.

6. Compressor Runs Continuously

• If the compressor never stops running, it may not be building or maintaining pressure.

• Could indicate leaks, worn components, or failure of the governor (which controls on/off cycles).

7. Air Leaks in the System

• Hissing sounds from tanks, lines, or fittings.

• Often caused by a weak compressor failing to maintain pressure.

8. Reduced Braking Performance

• Longer stopping distances.

• Brake pedal feels “soft” or “spongy.”

• In extreme cases, brakes may not engage at all.