What to Inspect When Buying a Used Car

Most used car disappointment is predictable. Not all of it is avoidable, but a large part of what goes wrong in the first six months of ownership was visible at the time of purchase, to someone who knew what to look at. This is what that inspection looks like.

Before you even open the door

Stand at the rear corner of the car and look along the bodywork in raking light, meaning light coming from the side rather than from above. Ripples in the paintwork that are invisible from directly above become obvious from this angle. A door, wing or boot lid that has been filled and resprayed will show a different surface texture and sometimes a slight colour mismatch. You are not looking for evidence that the car has ever had minor cosmetic work. You are looking for evidence of structural damage, which shows itself as crumpling or a fill that is thicker than surface-level.

Check the panel gaps. Open every door, the bonnet and the boot. The gaps between adjacent panels should be even and consistent. Uneven gaps, one side wider than the other, or gaps that taper, are evidence that either the car has been in a collision or the panels have been replaced. Compare both sides. Open the bonnet and look at the inner wing structure: those ribbed areas should be straight. Any kinking, buckling or fresh paint on the inner wing means the front end has taken an impact.

Look at the tyres. Not just the tread depth, which you can check quickly with a twenty-pence piece, but the wear pattern. A tyre worn heavily on one edge indicates a geometry problem: either camber is out of specification, or the tyre has been run underinflated for a long time. Tyres worn heavily in the centre were overinflated. Uneven tread depth from left to right means the car has not been aligned regularly. Any of these adds a cost to the purchase price that the seller has not factored in.

Under the bonnet

The engine bay of a car that has been maintained honestly is not necessarily clean. Workshop clean engine bays are sometimes a sign of a pressure wash before sale. What you want is an engine bay that is consistently dirty, not selectively dirty. Look at the underside of the oil filler cap. Remove it and look at the underside. Some light discolouration is normal. Thick, creamy, white or brown mayonnaise-like deposits on the underside of the cap are an indicator of coolant mixing with oil. That can mean a head gasket failure, which is a four-figure repair on most engines.

Check the coolant reservoir. The coolant should be translucent: green, blue or pink depending on the type. Murky brown coolant has not been changed in years and will contain scale and acidic breakdown products that corrode the cooling system. While you are here, look for any oil residue around the coolant cap or in the coolant itself. An oily sheen on the surface of the coolant is the other side of the head gasket warning.

Pull the oil dipstick, wipe it, reinsert it fully and pull it again. The oil level should be between the minimum and maximum marks. The oil itself should be either honey brown or dark brown to black depending on when it was last changed. Metallic glitter in the oil is a bad sign. Creamy oil points to the same head gasket problem as the filler cap. Grey oil on a diesel usually means water from condensation, which can happen when a car is driven only short journeys and the engine never fully warms up.

The test drive

A test drive has one job: producing sensations that were not present when the car was stationary. Start the engine from cold if possible. A well-maintained car should start cleanly. Listen for any rattling on start-up that fades as oil pressure builds: a short rattle that clears within a second is acceptable on some older engines, but one that persists suggests wear in the valve train.

Drive slowly over a speed bump with the window down and the radio off. Clunks from the suspension are more audible than felt at low speed. A front clunk from the centre of the car is often a drop link or anti-roll bar bush. A clunk from directly below the driver's seat is often a rear anti-roll bar. These are seventy to one-hundred-and-fifty pound jobs. A clunk from a wheel during steering input suggests a worn ball joint or track rod end. Those are safety items and should be costed before purchase.

On an open road, take both hands off the wheel briefly. The car should track straight. A car that pulls to one side has a geometry problem or an underinflated tyre. Apply the brakes firmly at thirty miles per hour. The car should stop in a straight line without the wheel vibrating or the pedal pulsing. A pulsing pedal is often warped rotors. Pull up a steep hill and sit for a moment with the car held on the footbrake rather than the handbrake. A spongy pedal that creeps toward the floor means the master cylinder is passing fluid internally.

Documents and history

A full service history is worth money. Not just in resale, but in information. A car with stamps from the same garage for its entire life has one story. A car with stamps from seven different garages in twelve years has seven different stories and you do not have access to any of them. Check the service intervals match the manufacturer's schedule. A car specified for annual oil changes that has stamps eighteen months apart has been shortchanged.

Run a used car data check before committing. These are available for six to fifteen pounds and tell you whether the car has any outstanding finance on it, whether it has been reported stolen, whether the mileage is consistent with previous recorded history, and whether it appears on any write-off registers. Outstanding finance on a used car means the previous owner still owes money to a lender using the car as security. That debt does not transfer with ownership on a private sale in the normal sense, but recovering the situation is complex and the lender has legal claims on the vehicle.

For more on what to look for in specific car types and age ranges, see the buying a car category. For a guide on what to do after purchase, see the maintenance section.