Pre-Trip Air Brake Inspection
9 free questions, part of the Air Brakes CDL practice test
The official pre-trip air brake inspection runs in order: check that the governor cuts the compressor out in the correct pressure range, run the one-minute air leakage test with the engine off, fan down air pressure to confirm the low air warning activates, then keep fanning to confirm the parking/emergency brake valve pops out at the right pressure. ELDT.io's free practice bank has 9 questions covering every step of the air brake pre trip inspection, including slack adjuster checks and the final air buildup test.
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Start Class A CDL Theory ($15)Questions about Pre-Trip Air Brake Inspection
What is checked during the governor cutout test on a pre-trip inspection?
With the engine running and wheels chocked, you let air pressure build and confirm the compressor cuts out, meaning it stops building pressure, within the correct range for that vehicle, generally around 120 to 135 psi.
How much air pressure loss is allowed during the air leakage rate test?
With the engine off, the key in the on position, the parking brake and tractor protection valve released, and the foot brake fully applied and held for one full minute, only a small, specified amount of pressure loss is allowed. Losing more than that means there's a leak that needs to be fixed before the vehicle is driven.
How do you check slack adjusters during a pre-trip inspection?
With the vehicle parked, wheels chocked, and parking brakes released, pull hard by hand on each reachable slack adjuster. If the pushrod moves too far where it attaches to the slack adjuster, it likely needs adjustment.
What does it mean if an automatic slack adjuster needs manual adjustment?
Vehicles built since 1994 use automatic slack adjusters that are supposed to self-adjust during normal full brake applications. If one still needs to be adjusted by hand to get back into spec, that usually points to a mechanical problem with the brake, not just normal wear.