CDL General Knowledge TestAir Brakes (if applicable)Easy
A driver hears a loud 'whoosh' sound from the air brake system every few minutes. The air pressure gauge remains stable within the normal operating range. What does this sound most likely indicate?
- AA major leak in the primary air tank.
- BA faulty low air pressure warning buzzer activating.
- CThe air compressor engaging to build pressure.
- DThe air dryer purging accumulated moisture and contaminants.
Show answer & explanationAnswer & explanation
Correct answer: D. The air dryer purging accumulated moisture and contaminants.
A regular 'whoosh' or 'hiss' sound that occurs intermittently, while the air pressure remains stable, is characteristic of the air dryer purging moisture and contaminants, which is a normal function.
Why the other options are wrong
- A. A major leak in an air tank would cause a continuous hiss and a noticeable drop in air pressure.
- B. A faulty warning buzzer would produce a buzzing sound, not a 'whoosh', and would be associated with low pressure.
- C. The air compressor engaging typically sounds like the engine laboring slightly more, not a distinct 'whoosh' sound, and it would be followed by increasing pressure.
Air Dryer Purge
The periodic release of accumulated moisture and contaminants from the air dryer to maintain air system cleanliness.
- Produces a distinct 'whoosh' sound.
- Occurs intermittently during normal operation.
- Essential for preventing water and oil buildup.
Memory trick: Whoosh! It's Just the Dryer, Don't Be a Cryer!