Vehicle Systems and Pre-Trip Inspection
Vehicle Systems and Pre-Trip Inspection tests your knowledge of the engine, cooling, electrical, brake, air, tire, and coupling systems and the checks that prove they are safe.
Core rules
- Check engine oil, coolant, belts, hoses, battery, and leaks. Look for cracked belts, soft hoses, and fluid trails.
- Inspect tires for tread, sidewall damage, tread separation, and proper inflation. Check rims, lug nuts, and spacers.
- Air brake tests: with engine off and brakes released, static leakage should not exceed 3 psi per minute on a single vehicle or 4 psi per minute on a combination. Applied leakage should not exceed 3 psi per minute.
- The low-pressure warning must activate before pressure drops below 60 psi. Spring brakes should set between 20 and 45 psi.
- Check slack adjusters, brake chambers, hoses, and coupling security. Do not manually adjust slack adjusters unless qualified.
Worked example
With the engine off and brakes released, pressure drops 5 psi in one minute on a single vehicle. That exceeds the 3 psi per minute allowable static leak rate, so the air system fails and the vehicle must be repaired before use.
Traps
Not chocking wheels; skipping the low-pressure warning test; assuming gauges are accurate; overlooking a cracked belt or soft hose.