Buying a Used Car: The 20-Minute Inspection

A professional pre-purchase inspection is money well spent, and you should have one before buying any used car. But you do not want to pay for an inspection on every car you look at. This is the twenty-minute screen that tells you whether a car is worth taking further.

None of it requires tools beyond your phone and a magnet, and none of it requires knowing much about cars.

See it in daylight, dry, and cold

Insist on all three. Wet paint hides swirl marks, scratches and mismatched panels. Artificial light hides colour differences. And a warm engine hides the cold-start problems that are often the whole reason the car is being sold.

If the seller has already warmed the engine before you arrive, that is worth noting. It may be courtesy. It may also mean you will not hear what the car sounds like on a cold start, which is when worn components are loudest. Ask to come back, and treat reluctance as information.

Paperwork before mechanics

Check the registration certificate against the car, verifying the chassis and engine numbers physically stamped on the vehicle rather than only what the document says. Confirm the seller's name matches the RC, or that they hold a clear authority to sell.

Then check for finance. A car under an active loan carries a hypothecation endorsement on the RC, and it cannot be transferred cleanly until that is closed and a no-objection certificate issued. Buying a hypothecated car without that document is a genuine problem rather than a formality.

Verify insurance status and check the claim history, which indicates past damage. Check that pollution certification is current. And on a diesel in particular, be aware of the age restrictions that apply in some cities, because a car that cannot legally be registered where you live is worth nothing to you regardless of condition.

The walk-around

Stand at each corner and look along the panels at a shallow angle rather than straight on. Reflections reveal ripples, filler and repaint that are invisible face-on.

Then check the panel gaps. Factory gaps are even and consistent; a gap that narrows along its length usually means the panel has been removed and refitted, or that something behind it is bent. Compare each side against the other, since asymmetry is easier to spot than absolute error.

Look for colour mismatch between adjacent panels, especially in direct light, and check that the texture of the paint matches. Refinished panels frequently have slight orange-peel texture that factory paint does not.

A cheap magnet is useful here. It sticks to steel and will not stick over a thick layer of body filler. Run it lightly along the lower sections of doors, sills and arches, which is where filler most often hides rust.

Underneath and inside the openings

Open the doors, boot and bonnet and look at the shut faces and the edges, which are rarely repainted properly and where overspray shows. Look for overspray on rubber seals and on the underside of the bonnet, which indicates repair work.

Lift the boot carpet and check the spare wheel well. This is where accident damage is hardest to hide, because a rear impact deforms the floor and the repair is seldom cosmetic. Ripples, welding or fresh underseal in that area warrant serious explanation.

Look under the car with your phone torch. You are looking for fresh fluid leaks, heavy corrosion on structural members, and any area of underseal that looks newer than the rest, which is a common way of covering repair or rust.

The engine bay, cold

Before anything is started, pull the oil dipstick. The oil should be translucent amber to dark brown. Milky or foamy oil suggests coolant entering, which points at a head gasket and should end the conversation.

Open the oil filler cap and look at the underside. A thick, mayonnaise-like deposit is the same warning.

Check the coolant in the expansion tank: brightly coloured and translucent is right, brown or oily is not. Look for corrosion around the battery terminals, and check the date on the battery.

Then look at how clean the bay is. Slightly dusty is normal and honest. A steam-cleaned engine bay on an older car sometimes means pride and sometimes means a leak was washed away last week.

The cold start

Stand outside the car and watch the exhaust as it starts. A brief puff of vapour on a cold morning is condensation and normal. What is not normal:

• Blue smoke means burning oil, indicating worn valve stem seals or piston rings
• Thick white smoke that persists rather than dispersing suggests coolant entering the combustion chamber
• Black smoke indicates over-fuelling

Listen for rattles in the first few seconds, which can indicate timing chain wear, and for any ticking that does not settle as oil pressure builds. Watch the dashboard during the ignition self-test: every warning light should illuminate briefly and then go out. A light that never illuminates at all may have had its bulb removed to hide a fault.

The drive

Drive it yourself, and include varied conditions rather than a loop around the block. You want low speed, an open stretch, and at least one hard braking application from a reasonable speed on a clear road.

With the radio off and windows down, listen. Then check specifically for a car that pulls under braking, which suggests a sticking caliper; vibration through the steering at speed, which suggests wheel balance or worse; knocking over bumps, which points at suspension; and on an automatic, any hesitation or harshness between gears.

Test everything electrical while you are in there. Windows, mirrors, central locking, air conditioning, lights, wipers, horn and the infotainment. Individually these are minor; collectively they tell you how the car has been maintained.

Findings that should end it

Some things are negotiating points and some are reasons to walk away. Treat these as the second category: evidence of structural or chassis repair, milky oil or coolant contamination, a mismatch between the documents and the physical chassis or engine numbers, an unresolved hypothecation, or an odometer reading that contradicts the service records and the general wear of the pedals and steering wheel.

If the car passes this screen, then pay for a professional inspection. What you have done is avoid paying for nine of them.