CDL Air Brakes TestAir Brake System PartsHard
A driver is inspecting the air storage tanks on a commercial vehicle. They notice that the automatic drain valve on one of the tanks is continuously expelling air, even after the system has reached full pressure. What is the most likely consequence of this issue?
- APremature activation of the anti-lock braking system (ABS).
- BIncreased workload for the air compressor and potential for air pressure loss.
- CExcessive moisture build-up in the air lines.
- DReduced braking force due to contaminated air.
Show answer & explanationAnswer & explanation
Correct answer: B. Increased workload for the air compressor and potential for air pressure loss.
A continuously expelling automatic drain valve indicates a leak. This leak will cause the air compressor to work harder and more frequently to maintain system pressure, potentially leading to compressor overheating and wear, and could result in a dangerous loss of air pressure if the leak is severe.
Why the other options are wrong
- A. ABS activation is related to wheel speed differentials during braking, not directly to a slow, continuous air leak from a drain valve.
- C. Automatic drain valves are designed to expel moisture; if it's continuously expelling, it's losing air, and the moisture issue is secondary.
- D. While contaminated air can reduce braking force, a continuous air leak from a drain valve primarily causes pressure loss, not necessarily contamination.
Air Storage Tank Drain Valves
Valves located at the bottom of air storage tanks, used to drain moisture, oil, and contaminants that collect in the tanks. They can be manual (pull-cord) or automatic (expel moisture when compressor unloads).
- Essential for removing moisture and preventing corrosion/freezing.
- Automatic valves typically purge air/moisture when the compressor unloads.
- A continuous leak indicates a faulty valve or seal.
Memory trick: Always Draining? Compressor's Straining!