Models · Audi
Audi S4 B6 buying guide
The B6 S4 was built from 2003 to 2005 as a saloon, Avant and cabriolet, with a naturally aspirated 4.2 litre V8 and permanent quattro four-wheel drive. It's a durable car when serviced properly, and the main checks centre on the engine's timing chains and its oil.
The versions
- 4.2 V8 40-valve (BBK), 344PS
- 6-speed manual or 6-speed Tiptronic automatic, with automatics the more common
- Permanent quattro four-wheel drive with a Torsen centre differential
- Saloon, Avant and cabriolet bodies, with saloons the most common and Avants rare
What to check on a B6 S4
3 model-specific things to look at when you view one. They're a starting point, not the full inspection.
A rattle from the back of the engine
What to look for: Start the engine from fully cold and stand near the windscreen, where the back of the engine meets the bulkhead. Listen for a rattle or chattering that carries on after start-up, or comes back when the engine is warm and blipped.
Why it matters: The camshaft chains run at the back of this engine, with plastic guides and a tensioner that can wear from around 100,000 miles. Replacing them means taking the engine out, so it's the most important single check on the car. Many engines never need it, and regular oil changes are the best protection.
Oil changes and oil level
What to look for: Check the dipstick and ask how much oil the car uses between services. In the history, look for regular oil changes with 0W-40 or 5W-40 oil, rather than the longest intervals the service indicator allowed.
Why it matters: The chain tensioners depend on clean oil at the right pressure, so the oil record tells you something about the chains. A level that drops noticeably can point to a failed crankcase breather valve, which is a routine repair, and in rarer cases to wear in the cylinders.
Misfires and coil packs
What to look for: With the engine warm and idling, feel for a regular pulse or shake through the car, and watch for the engine warning light flashing under load.
Why it matters: Each cylinder has its own ignition coil, and a failing coil is a common cause of misfires on this engine. It's an inexpensive repair, but a diagnostic scan will confirm which cylinder before you agree a price.
Also in the full guide
- Oil leaks from the cam covers
- Power steering hoses
- Gearbox and differential fluids
- The cold start, test drive and paperwork checks for the exact version you're viewing
The full guide to the B6 S4
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
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.