Truck post-start checks: what to check once the engine's running

By AJ Sakai, Director, Transport & Logistics Hub (TLH) · Published

The pre-start walk-around tells you the truck looks right. The post-start checks tell you it works right: brakes, air, gauges and warning systems, which you can only test with the engine running. They take a few minutes in the cab before you roll out of the yard, and they're your last chance to find a problem while the truck is still parked.

1. Warning lights and gauges

When you turn the key, the dash lights come on as a self-test and should then go out once the engine's running. After start-up:

  • No warning lights left on. That includes ABS/EBS, engine, oil pressure, charging and brake warnings.
  • Oil pressure rises to normal within seconds.
  • Voltage/charging gauge shows the alternator is charging.
  • Coolant temperature starts climbing normally as the engine warms.
  • Fuel level is enough for the run.
  • AdBlue/DEF level is OK (if fitted), and there are no emissions system warnings.

A warning light that stays on is a defect. Record it and get it checked before driving.

2. Air pressure build-up (air-braked vehicles)

With the engine running, watch the air gauges climb.

  • Build-up time: the system should charge in a reasonable time. As a benchmark, the NSW vehicle inspection procedure requires an air system to charge from empty to 80% of governor cut-out pressure within 5 minutes. A truck that's noticeably slower than usual may have a compressor or leakage problem.
  • Governor cut-out: the compressor should stop pumping at the normal operating pressure for that vehicle (check the manufacturer's figure) and cut back in as pressure drops.
  • Both circuits: on dual-circuit systems, check both gauges rise and hold.

3. Low-air warning test

With the system at full pressure and the engine off (or idling, per the manufacturer's procedure), pump the brake pedal to bleed pressure down and confirm the low-pressure warning (buzzer and/or light) activates. For ADR 35-compliant vehicles, the warning should operate before pressure drops below about 400 kPa (60 psi) in either circuit. Then let the system recharge.

If the warning doesn't come on, the driver gets no notice of a brake air failure. Don't drive it.

4. Air leakage check

With full pressure, brakes released and engine off, listen for leaks and watch the gauges for a minute. Then hold a full brake application and watch again. Any obvious, steady pressure drop, or an audible leak, needs to be found and fixed before driving. Use the manufacturer's leakage limits for your vehicle.

5. Park brake and service brake test

  • Park brake hold: with the park brake applied, gently try to move off under light throttle. The vehicle should not move.
  • Service brakes: once moving at walking pace in the yard, apply the brakes firmly. The truck should pull up straight without pulling to one side, and the pedal should feel normal.
  • Trailer brakes (combinations): test the trailer brakes using the trailer brake control, to confirm the trailer is pulling up too.

6. Steering and the first few metres

  • Steering feels normal, with no excessive free play, heaviness or noise.
  • No new noises, vibrations or smells as you move off.
  • Mirrors are adjusted for this driver.

What to do if something's wrong

Same rule as the pre-start: record it, report it straight away, and don't dispatch a vehicle with a safety defect. Brake, air and steering faults are stand-down defects, not "let the workshop know at the end of the week" defects.

How TrakkHQ handles it

TrakkHQ's pre-shift inspection runs in the driver app. Each check is recorded against the truck and driver with a timestamp, and the office has a per-item audit view with PDF export, so start-of-shift checks are on record, not on a scrap of paper in the cab.

Book a demo

FAQ

Pre-start or post-start: which comes first?
Pre-start first, engine off: the walk-around. Then start the engine and do the post-start checks before moving off.

Do post-start checks apply to trucks without air brakes?
Yes. Warning lights, gauges, park brake and service brake tests apply to every vehicle. The air-specific steps apply to air-braked vehicles.

Where do the brake test numbers come from?
From vehicle inspection procedures used by inspectors. Your vehicle manufacturer's figures take priority for your specific truck.

Sources

This guide is general information, not a substitute for your vehicle manufacturer's procedures or formal driver training.