CDL Air Brakes TestUsing Air BrakesMedium
During a pre-trip inspection, a driver checks the air brake system for leaks. With the engine off and the brakes applied, the air pressure loss rate should not exceed a certain amount. For a single vehicle, what is the maximum permissible air pressure drop in one minute?
- ALess than 5 psi
- BLess than 3 psi
- CLess than 2 psi
- DLess than 4 psi
Show answer & explanationAnswer & explanation
Correct answer: B. Less than 3 psi
This test checks for leaks in the service brake system. A drop exceeding 3 psi in one minute for a single vehicle indicates a leak that needs to be addressed before operation.
Why the other options are wrong
- A. 5 psi is the maximum permissible drop for a combination vehicle, not a single vehicle.
- C. 2 psi is a good target, but 3 psi is the regulatory maximum for a single vehicle.
- D. 4 psi is above the regulatory maximum for a single vehicle.
Air Brake Leakage Test (Single Vehicle)
A pre-trip inspection procedure to check for air leaks in a single commercial vehicle's air brake system by measuring pressure drop over time with the engine off and brakes applied.
- Engine off, wheels chocked.
- Service brakes fully applied.
- Maximum 3 psi drop in one minute for a single unit.
Memory trick: Pressure Drop: 'Three' for a Truck, 'Five' for a Fleet!