How to Inspect a Used Truck

You do not need to be a mechanic to spot most of the problems that make a used truck a bad buy. You need time, daylight, a cold engine and a methodical approach. Allow at least an hour. If you are not confident, or the truck is a big purchase, pay an independent heavy vehicle mechanic to do a pre-purchase inspection: it costs far less than one major repair.

What to bring

• A torch, a rag, gloves and something to kneel on.
• A tyre tread depth gauge.
• Your PPSR certificate and the truck buying checklist.
• Someone to watch the exhaust and lights while you start and operate the truck.

Step 1: Check the paperwork matches the truck

Find the VIN and compliance plates and compare them with the registration papers, the service records and your PPSR search. Check the seller is the registered owner or can show their authority to sell. If anything does not match, stop here until it is explained.

Step 2: Walk around from a distance

Stand back and look at the truck on level ground. Does it sit level side to side and front to back? Do the panels line up, and does the paint match from panel to panel? Mismatched paint, overspray on rubber seals and uneven gaps suggest accident repairs, so ask about them.

Step 3: Get underneath

• Chassis rails: look along them for kinks, cracks, welds, heat marks and heavy rust, particularly around spring hangers, crossmembers, the fifth wheel and body mounts.
• Leaks: oil from the engine, gearbox and diffs; coolant; hydraulic oil on tippers and cranes. Fresh cleaning in one spot can hide a leak.
• Suspension: airbags for cracking and leaks, springs for broken leaves, shock absorbers for leaks, and bushes for wear.
• Driveline: grab the tail shaft and twist it to feel for play in uni joints and the centre bearing.
• Exhaust and after-treatment: damage or leaks around the DPF and AdBlue components.

Step 4: Tyres, wheels and brakes

Measure tread depth on every tyre and look for uneven wear: wear on one edge of the steer tyres points to alignment or kingpin problems; cupping points to suspension. Check for mismatched tyres across duals, cuts and bulges, and rust trails from wheel nuts, which can indicate loose wheels. Look at brake linings and drums or discs where you can see them.

Step 5: The engine, cold

• Check the oil level and look under the filler cap for milky residue, a sign of coolant in the oil.
• Check the coolant for an oily film, a sign of oil in the coolant.
• Have your helper watch the exhaust as you start it. A puff of smoke that clears is normal; persistent blue smoke (burning oil), white smoke that does not clear (coolant) or heavy black smoke (fuelling or turbo problems) is not.
• Listen for knocks, rattles and injector noise as it warms.
• Once warm, remove the oil filler cap or look at the breather: a steady stream of fumes (blow-by) indicates worn rings or liners.

Step 6: In the cab

Turn the key and check all warning lights come on and then go out. Watch the air pressure build-up time and listen for leaks when it reaches pressure. Test lights, wipers, heater, air-conditioning, horn and mirrors. Compare wear on the seat, pedals and steering wheel with the claimed kilometres. If you can, have the truck scanned for stored fault codes.

Step 7: Test drive

Drive it on roads like the ones it will work on, and loaded if possible. Check that:

• it pulls strongly through the gears and holds speed and temperature on a hill;
• gears select cleanly up and down and the clutch does not slip or judder;
• it brakes in a straight line and the exhaust brake or retarder works;
• steering tracks straight without wandering or vibration; and
• there is no diff whine, driveline clunk or knocking over bumps.

After the drive, look underneath again for new leaks and check the engine for blow-by now it is hot.

Step 8: Body and equipment

Operate everything the truck is being sold with. Raise a tipper body fully and watch the hoist for leaks or jerky movement; run a crane through its full range; cycle tailgate loaders and hook-lifts; check that a fridge unit reaches temperature. Inspect the body floor, hinges, locks and curtains, and check equipment certification where it applies.

After the inspection

Make a list of everything you found and price the repairs. Use it to negotiate, or to walk away. A seller who is reluctant to let you inspect properly, or to allow a mechanic to look, is telling you something. When you are ready, our used truck buying guide covers the remaining checks, and you can browse used trucks for sale near you.