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Daily inspection test
Exterior Items

2. Audible air leaks

You must know that it’s necessary to check for leaks regularly, and a vehicle has this minor defect when any air leak can be heard.

Air loss rate exceeds the prescribed limit

You must know the proper method for testing the air-loss rate, and that a vehicle has this major defect when the air pressure drops in one minute more than the prescribed limit of:

    • 28 kPa (4 psi) in one minute for Class A
    • 21 kPa (3 psi) in one minute for Class D


    • Tell the examiner, “For any air leaks heard at any time, I would conduct the air-loss rate test.”
    • Ensure the vehicle is secured by wheel chocks.
    • Release all spring parking/ emergency brakes.
    • Ensure the air-system pressure is between cut-in and cut-out values (80-145 psi); shut off the engine and turn the key on (if required).
    • Hold the brake pedal in the fully applied position.
    • Observe the air pressure gauges for one minute and note any change. (Disregard the initial pressure drop and begin test after the pressure has stabilized.)