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Inspection Session

We check out what's involved in an on-site mechanical inspection.

By Michael Knowling

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At a glance...

  • On-site mechanical inspections
  • What they do
  • The costs
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This article was first published in 2004.
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A mechanical inspection is essential when buying a used car. Why? Well, an inspection reveals any hidden problems and - just as importantly - every small fault gives you terrific bargaining power.

A workshop inspection is typically a headache for sellers to arrange but, thankfully, there is an option – an on-site inspection. On-site inspections are usually performed at a private residence or a place of work – anywhere with room to move and firm ground.

In this article we follow South Australia’s MotaCheck Pty Ltd during an on-site vehicle inspection.

On-Road Test

The first step is to perform an on-road vehicle test. This is best done with the vehicle cold, so the technician can identify any problems that might not be apparent with the engine at normal operating temperature. Valvetrain clatter and poor drivability are relatively common at low coolant temperature.

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Once the engine is warm, the technician will drive the car at various rpm and load combinations. Engine smoke, back-fires, detonation and any unhealthy engine noises are noted. Estimation is also made whether the vehicle is performing to a suitable standard.

The on-road test also reveals gearbox/clutch, differential, steering, suspension, wheel alignment and brake problems. The vehicle is typically driven for about 15 minutes.

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Note that, in this case, the vehicle was unable to be road tested: MotaCheck will not road test a vehicle that is unregistered or unroadworthy.

Vehicle Inspection

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Once the vehicle returns from its road test (or once the engine has been warmed up while parked), the technician opens the bonnet and checks for noises, leaks or anything else amiss with the running engine.

The cooling system is also checked while the engine is running. The radiator cap is (carefully) removed and the coolant is checked for bubbles and sludge. If there are signs of a blown head gasket, cracked head or block, the cooling system is pressure tested. The humble radiator cap is also given a visual check.

The engine can now be switched off and allowed to cool – it’s time to check the body and interior.

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Interior inspection involves checking the operation of the heater and air conditioning, demister, gauges, washers and wipers, power windows and all interior features. Seatbelts, mirrors, seats, the steering column and horn are assessed from a safety point of view. General observations are also made about the condition of the trim.

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This particular vehicle is fitted with a manual pop-up sunroof, which is inspected for effective sealing and rust around the aperture.

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The body inspection is a visual assessment of panel and paint condition with specific attention to rust spots. The lower edge of the doors, inside the spare wheel well and other common rust areas are checked. All exterior lights are also checked for operation.

And now it’s time to check what’s underneath.

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MotaCheck says the underside inspection is the most important part of a mechanical inspection – it doesn’t matter how good the engine is if the chassis is about to fall apart! The chassis rails and floorpan are closely examined for rust and any signs of accident damage are noted. We’re told that many Japanese import cars have underside damage after being moved by a forklift.

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While checking the vehicle’s underside, the technician inspects all bushes, shock absorbers, springs and suspension hardware. The steering rack and arms are checked along with boots and the condition of the power steering hoses.

The condition of the brake lines, disc and pad thickness are inspected from beneath the vehicle and from the outside of the wheels. The differential(s) are also checked for leaks and, depending on the drive configuration, the tailshaft bushings/joints or the driveshafts/CVs are checked. A visual inspection is also made of the exhaust system, with attention paid to the condition of cat convertor and mufflers.

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Next, the wheel rims are inspected for kerb damage and all tyres (including the spare) are checked using a tread depth gauge. The sidewalls and carcass are also inspected for deterioration.

And now we return to the engine, which has had a chance to cool.

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An important guide to engine condition is the cranking compression of each cylinder. The first step to test the compression is to remove the spark plugs – and, while they’re out, these are checked for oil deposits and the tell-tale signs of improper air-fuel mixtures.

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A compression gauge is screwed into each spark plug opening and the compression is measured while the engine is being cranked with the starter motor. Compression figures vary in relation to the compression ratio of the engine – the technician will know what compression value is suitable for a particular vehicle. Each cylinder should have roughly the same compression.

The final phase of inspection is a thorough under-bonnet check.

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The engine is inspected for oil, coolant or fuel leaks, the drive belt condition is checked and the battery voltage is measured. Radiator, air conditioning and oil cooler cores are inspected and all fans are checked for operation. Note that (where fitted) the condition of the cam belt is not included as part of a typical mechanical inspection.

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Of course, the level and condition of the engine oil and transmission fluid is also checked.

Vehicle Report

Once the on-road test and inspection have been completed you are presented with a mechanical inspection report.

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MotaCheck’s mechanical report is three pages in length - longer if the car has lots of problems! Each item that requires attention is marked with an E (Early attention recommended), R (Requires repair or minor adjustment) or M (Minor wear – components serviceable but require monitoring for further deterioration). A tick is allocated to each item that is serviceable.

Note that all items marked with a letter are explained in brief detail. For example...

Item                              Category           Description

Wipers Front/Rear          -R-                    Rear blade needs replacement

Cost and Availability

Depending on the category of vehicle, the cost for the mechanical inspection varies.

A basic four or six-cylinder vehicle starts at AUD$120, an imported turbo car costs AUD$125-$130 and a turbo-diesel 4WD reaches AUD$160. MotaCheck may apply a surcharge if the vehicle is outside the Adelaide metropolitan area.

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Note that reinspections of a particular vehicle cost only AUD$40. A reinspection might be required after the seller claims to have fixed problems found in the initial inspection. Reinspections are also performed on vehicles nearing the end of their warranty period.

MotaCheck is available to inspect cars six days a week (excluding Sundays) and inspections can usually be arranged within a day. Be aware, though, Mondays and Tuesdays are the busiest days – many people see a car on the weekend, get it inspected Monday/Tuesday and buy the next day.


MotaCheck Pty. Ltd. (South Australia)
1300 1300 35

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