CDL Air Brakes TestAir Brake System PartsHard
A driver notices that the air compressor on their commercial vehicle is taking an unusually long time to build air pressure from 85 psi to 125 psi. After checking for external leaks, none are found. What internal component of the air compressor could be worn, causing this issue?
- AThe safety relief valve.
- BThe unloader valves.
- CThe air compressor governor.
- DThe piston rings or valves within the compressor.
Show answer & explanationAnswer & explanation
Correct answer: D. The piston rings or valves within the compressor.
If the air compressor itself is worn, specifically its internal components like piston rings or valves, it will lose efficiency and take longer to compress air and build pressure, even without external leaks.
Why the other options are wrong
- A. The safety relief valve is for over-pressurization; it doesn't affect the compressor's ability to build pressure, only to release it if too high.
- B. Faulty unloader valves would cause the compressor to either not pump air at all or to continuously pump beyond cut-out, not just slow build-up.
- C. A faulty governor would affect the cut-in/cut-out points, not the rate at which pressure builds between those points.
Worn Air Compressor Internal Components
Deterioration of parts inside the air compressor (e.g., piston rings, intake/exhaust valves) that reduces its efficiency and ability to compress air, leading to slow pressure build-up.
- Results in longer build-up times.
- Can be a progressive issue.
- Requires compressor rebuild or replacement.
- Often accompanied by increased oil consumption or unusual noises.
Memory trick: Piston's weak, valves may leak, compressor's tired, a slow air peak.