CDL Air Brakes TestInspecting Air Brake SystemsMedium
During a pre-trip inspection, a driver performs a static air leak test (engine off, parking brake applied). After the initial pressure drop, the air pressure should not drop more than what amount in one minute for a straight truck or bus?
- A3 psi
- B1 psi
- C2 psi
- D4 psi
Show answer & explanationAnswer & explanation
Correct answer: C. 2 psi
For a straight truck or bus, during a static air leak test (engine off, parking brake applied), the air pressure should not drop more than 2 psi in one minute after the initial pressure drop from applying the parking brake.
Why the other options are wrong
- A. 3 psi is the maximum allowed for a straight truck/bus during the applied service brake test, not the static test.
- B. 1 psi is too strict; 2 psi is the standard limit for a straight truck/bus in this test.
- D. 4 psi is the maximum allowed for a combination vehicle during the applied service brake test, not a straight truck/bus static test.
Static Air Leak Test (Straight Truck/Bus)
A test performed with the engine off and parking brake applied to check for air leaks in the primary air system of a straight truck or bus.
- Max 2 psi drop in 1 minute (after initial parking brake drop).
- Engine off, parking brake applied.
- Checks for leaks in lines, tanks, and components not under service brake pressure.
- For combination vehicles, this limit is also 3 psi.
Memory trick: Static truck, two psi luck!