CDL Air Brakes TestAir Brake System PartsEasy
During a pre-trip inspection, a driver notices moisture and oil residue draining from the air tank's manual drain valve. What does this indicate?
- AThe air compressor is over-lubricated.
- BThe safety valve is not seating properly.
- CThe brake pedal valve is leaking internally.
- DThe air dryer is malfunctioning or absent.
Show answer & explanationAnswer & explanation
Correct answer: D. The air dryer is malfunctioning or absent.
Air dryers remove moisture and oil contaminants from the compressed air before it enters the storage tanks. The presence of moisture and oil in the tanks indicates the air dryer is not performing its function properly.
Why the other options are wrong
- A. While an over-lubricated compressor could contribute to oil, the primary system for removing both moisture and oil before the tanks is the air dryer.
- B. A safety valve issues would lead to air leaks or over-pressurization, not the presence of contaminants in the tank.
- C. A leaking brake pedal valve would cause air loss during braking, not the accumulation of moisture and oil in the tanks.
Air Storage Tank Draining
Air storage tanks must be drained daily to remove water and oil that condense from compressed air, preventing system damage and freezing.
- Water and oil are normal byproducts of air compression.
- Draining prevents corrosion, freezing, and brake system contamination.
- Automatic drain valves exist, but manual checks are still important.
Memory trick: Wet tank, bad dryer; clean tank, good dryer.