Home › CDL Practice Tests › Air Brakes Questions › Question 78
Why must the engine be off during leakage tests?
- A.So the compressor cannot replace lost air and hide the true leakage rate
- B.To save fuel during the inspection
- C.Because the gauges do not work with the engine on
- D.So the parking brakes set automatically
Correct answer
A. So the compressor cannot replace lost air and hide the true leakage rate
Why
A running compressor can keep up with a small leak and make a defective system look healthy. Turning the engine off isolates the stored air so every psi lost is visible on the gauge.
Manual topic: Air Brakes - Air Leakage and Brake Tests · From the Air Brakes practice bank (AB-078).