Used Audi A3: Common Problems and Which Years to Buy

Rust. Check the wheel arches, sills and tailgate for bubbling paint or rust. Rust starting at the edges usually spreads underneath long before it shows on the surface. A line of fresh paint along a sill edge can be hiding a repair.

Crash repair. Sight down each panel gap and check paint colour matches across adjoining panels and door jambs. Uneven gaps or overspray on rubber seals point to earlier crash repair. A gap that narrows at one end usually means a panel has been refitted.

Headlights. Test every light including indicators, brake lights and reverse lights, and check xenon or LED units light up evenly with no flicker. A flickering or dim LED unit is expensive to replace. Cloudy or cracked lenses can also let in moisture over time.

Engine oil. Pull the dipstick and check the oil sits between the marks and looks brown, not black or gritty. Old black oil suggests services have been missed. Oil that smells burnt can point to a bigger problem brewing.

Coolant. Check the coolant reservoir is filled to its mark and the coolant looks clean, not rusty or oily. Frequent top-ups suggest a cooling system leak. Oily film on top of the coolant can mean a head gasket problem.

Brake fluid. Check the small brake fluid reservoir near the back of the engine bay; the fluid should be clear to light amber, not dark. Dark fluid means it hasn't been changed in a long time. Old brake fluid absorbs water and can reduce braking performance.

Cold start noise. Start the engine from cold and listen closely for a rattling noise for a second or two before it quietens. A rattle that lingers longer than a couple of seconds needs a mechanic's opinion. A persistent rattle at idle can mean expensive engine work ahead.

Tyre tread. Check tread depth on all four tyres is above the wear bars and wears evenly side to side. Wear on one edge only usually means the wheels are out of alignment. Uneven wear across the tyre can also point to worn suspension parts.

Suspension. Look at the shock absorbers for oily residue and bounce each corner of the car; it should settle quickly without bouncing more than once or twice. A corner that keeps bouncing means a worn shock absorber. Lowered cars should still meet your state's ride-height rules.

Chassis rust. Look underneath at the floor and suspension mounts for rust, bent metal or fresh welds. A patch of fresh black coating in just one spot can be hiding crash repair work. A gap narrower at the top points to a bent chassis.

Warning lights. Turn the key or press start without the engine running and check every dash light comes on, then goes out once the engine is running. An airbag, brake or engine light that stays lit needs an explanation. A light that's been taped over is a red flag.

Seatbelts. Pull each seatbelt out fully and let it retract, then click it into the buckle. It should move smoothly with no fraying or stiffness. A belt that won't lock when tugged sharply is a safety fail.

Quattro drive select. AWD: with the car running, cycle through the drive select modes and check the display changes response without error messages. A fault here can point to a driveline sensor problem. An error message in any mode is worth asking the seller about.

Infotainment. Test the touchscreen, Bluetooth pairing, reversing camera and parking sensors if fitted. A screen that freezes or sensors that don't respond can be a costly electrical fix. Dead pixels on the screen often get worse over time.

DSG gearbox. DSG: pull away from a stop on a flat road and again on a slight incline, feeling for shuddering or hesitation as the clutch engages. This should feel smooth every time, not just occasionally. Judder at low speed is a warning sign of clutch wear in the gearbox.

Manual clutch. Manual: in a higher gear at moderate speed, floor the accelerator briefly and feel if the revs rise faster than the car's speed. If so, the clutch is slipping. A slipping clutch will need replacing soon, which is a big cost.

Brakes. Brake firmly from speed on an empty road; the car should stop straight with a firm pedal and no pulling, pulsing or grinding. A grinding noise means the pads have worn down to metal.

Steering. Check the car tracks straight with no wandering, and the steering feels consistent at all speeds without going heavy or light suddenly. A whine or the assistance cutting in and out points to a power steering fault.

Diesel smoke. Diesel: accelerate hard from low speed and check the mirrors for black or blue smoke from the exhaust. Smoke under load points to an engine or turbo problem. A puff of smoke only on startup is less concerning than smoke under load.

Service history. Look through the logbook and receipts for stamps on time with no long gaps. Turbocharged engines and dual-clutch gearboxes don't forgive skipped services. Gaps in servicing are worth negotiating the price down for.

Timing chain service. Ask whether the timing chain tensioner has ever been replaced or inspected, as it's a known wear point on these engines. Get this in writing if the seller claims it's been done. A failed tensioner can cause serious engine damage if ignored.

Registration. Check the registration status online using the plate or VIN, and ask for a current roadworthy certificate if your state requires one for sale. An unregistered car can mean extra cost before you can drive it home.

Seller's ID. Check the seller's ID matches the name on the rego papers, and that the VIN matches across the papers and the VIN plate on the car. Any mismatch needs an explanation before you pay anything.