Models · Audi
Audi A6 C5 and allroad buying guide
The C5 A6 was built from 1997 to 2004 as a saloon and Avant, with four-cylinder, V6 and V8 petrol engines and the 2.5 TDI V6 diesel. The allroad quattro, added in 2000, is a raised Avant with air suspension. Well-kept cars are durable, and the known faults are specific and checkable.
The versions
- Petrol: 1.8T four-cylinder (150PS), 2.4 V6 (165PS, 170PS from 2001), 2.8 V6 (193PS, replaced by a 220PS 3.0 V6 in 2001), 2.7 twin-turbo V6 and 4.2 V8 (300PS)
- Diesel: 2.5 TDI V6, 150PS at first and 180PS from 1999 (engine code AKE among others)
- allroad quattro: 2.7 twin-turbo petrol (250PS), 2.5 TDI (180PS) or, from spring 2003, a 300PS 4.2 V8, with height-adjustable air suspension and an optional low-range gearbox on manual cars
- Front-wheel drive or quattro four-wheel drive; manual or five-speed automatic
- Saloon and Avant bodies
What to check on a C5 A6
3 model-specific things to look at when you view one. They're a starting point, not the full inspection.
2.5 TDI camshafts and rockers
What to look for: On a 2.5 TDI, start the engine and listen at the top of the engine for a tapping or clatter. On the drive, note any flat spots in power or smoke when you accelerate. Ask whether the camshafts and rocker arms have ever been replaced, and with which parts.
Why it matters: Early versions of this V6 diesel, up to about 2003, could suffer from poor lubrication of the camshafts. Gates, the belt maker, lists power loss, exhaust smoke, worn camshafts and broken rocker arms as the results, and in the worst case a snapped cambelt. Later engines with roller rocker arms don't have the problem.
Cambelt history
What to look for: Look through the invoices for the last cambelt change, with the date and mileage, and whether the tensioner and pulleys were replaced with it. On a 2.5 TDI, ask whether the injection pump belt was done at the same time.
Why it matters: The 2.5 TDI, the 1.8T, the 2.8 V6 and the 2.7 twin-turbo all drive their camshafts with a rubber belt, and a failed belt causes serious engine damage. The 2.5 TDI uses a hydraulic tensioner that has to be set correctly, so a belt change by a specialist who knows the engine is a sign of a car that's been looked after.
Front suspension arms and joints
What to look for: Drive slowly over speed humps and broken road with the window down, and listen for clonks from the front. At a steady speed, notice whether the steering feels vague or wanders. Look at the inner edges of the front tyres for uneven wear.
Why it matters: Worn control arms, steering joints and torn driveshaft boots at the front were the most common faults owners recorded on this generation, even with ordinary road use. Replacing the arms as a complete set is the usual fix, and fresh parts in the invoices are a good sign.
Also in the full guide
- Automatic gearbox behaviour
- allroad air suspension
- 2.5 TDI cooling fan and air flow sensor
- The cold start, test drive and paperwork checks for the exact version you're viewing
The full guide to the C5 A6
The CrankSight guide walks you round the car on your phone at the viewing, with every check for the exact version you're looking at: what to look for, where to find it, and what anything you find is likely to cost. As you go it builds an assessment of that car, and if you view more than one, it lines them up side by side.
£29 for the model, used on as many cars as you like, delivered within 72 hours or your money back.
Other generations
Audi A6 C6 and allroad · Audi A6 C7 and allroad · Audi A6 C8 and allroad
General points for the model, last checked October 2026. Every car is different, so treat this as a guide to what to look at, not a verdict on any car. CrankSight is independent and has no connection with Audi.