车内气刹检查怎么检查
Done from the driver's seat with the vehicle parked and the wheels chocked. This is the most heavily scored part of the pre-trip: the air brake (or hydraulic brake) check is an AUTOMATIC FAILURE if it is not explained and demonstrated correctly. Know and say the trigger numbers — they can vary slightly by manual and state.
分步检查
- 1
Governor cut-out / cut-in: with the engine running, build air pressure to governor cut-out (about 120–140 psi) and confirm the compressor stops; pump the brake down and confirm the governor cuts back in and the compressor resumes.
- 2
Air pressure build-up: on a dual air system, pressure should build from about 85 to 100 psi within 45 seconds at operating idle.
- 3
Static air leakage (engine off, brakes released): pressure loss no more than 2 psi in 1 minute for a single vehicle, or 3 psi in 1 minute for a combination.关键
- 4
Applied air leakage: fully apply and hold the foot brake; pressure loss no more than 3 psi in 1 minute for a single vehicle, or 4 psi in 1 minute for a combination.关键
- 5
Low-air warning: fan off pressure by pressing and releasing the brake; the low-air warning (buzzer/light) must come on before pressure drops below about 60 psi (some manuals/states say 55 psi).关键
- 6
Spring (parking) brakes: keep fanning the pressure down; the parking-brake valve should pop out and the spring brakes come on automatically between about 20 and 45 psi.关键
- 7
Test the parking brake: rebuild pressure, set the parking brake, and gently pull against it in a low gear — the vehicle should not move.
- 8
Test the service brakes: release the parking brake, roll forward about 5 mph and apply the brakes firmly — the vehicle should stop straight with no pulling, delay or unusual feel.
自动挂科与必做要点
- AUTOMATIC FAILURE if the air-brake check is not explained and demonstrated correctly — this is the highest-stakes part of the pre-trip.
- Say the trigger numbers: build 85–100 psi in 45 s; low-air warning before ~60 psi; spring brakes 20–45 psi; governor cut-out ~120–140 psi.
- Leakage limits: static 2 (single) / 3 (combination); applied 3 (single) / 4 (combination) — psi per minute.
- Chock the wheels before the rolling service-brake test.
常见错误
- Skipping or mis-ordering the check (an automatic fail).
- Quoting the wrong trigger numbers, or not saying them at all.
- Confusing the static vs applied leakage limits, or the single vs combination limits.
- Not chocking the wheels before the service-brake roll test.
为什么重要
Air brakes are what stop a fully loaded truck, and they fail gradually as air leaks — so this check proves the compressor keeps up, leaks are within limits, and the warning and spring brakes will protect you if pressure ever drops. That is why examiners fail the whole test if this check is done wrong.