Used car buying guide: Audi S4 (B6/B7)
7 June 2021 - autocar
You’ll simply adore the naturally aspirated V8 of a 2003-09 Audi S4 – so long as a few crucial plastic parts don’t break
"The Audi S4 you should never buy,” screams one web post on the Audi S4 B6 and B7 generations. Not an encouraging start to a buying guide dedicated to the model, but best we tackle this charge right away.
It refers to the fact that the engine has a timing chain rather than a timing belt. No problem there, given the reputation of chains outlasting belts, except that on the S4, the chain’s guides and tensioner are made of plastic. From around 100,000 miles, the material breaks down. Imminent failure is signalled by what victims call the ‘death rattle’ as the tensioner relaxes and the chain begins to wander before, in the worst case, jumping teeth and, well, you know the rest. Get to it early enough and you can replace the tensioner kit, but it’s an engine-out job so is expensive. Budget around £2500.
The S4 you should never buy indeed, except that many B6 and B7 S4s have gone through life without so much as a peep from the chain. Check their service histories and you’ll find they’ve been treated to regular changes of 0w40- or 5w40-grade oil. In any case, this kind of problem can be overstated and you wouldn’t want it to spoil the pleasure of finding a good S4, especially since it’s blessed with one of those rare things: a naturally aspirated V8.
It was launched in 2003 in saloon, cabriolet and estate (Avant) bodystyles. The all-alloy 4.2-litre motor produces 339bhp at a screaming 7000rpm and 302lb ft torque at a less shouty 3500rpm. Fitted with the standard Getrag six-speed manual gearbox (there’s an optional ZF automatic with paddles), an S4 can dispatch the 0-62mph sprint in 5.0sec. Quattro four-wheel drive and an electronic differential lock should take some of the credit here. As the revs rise, the engine emits a raucous howl. It’s the heart of the car and the reason you’d buy a B6- or B7-gen S4.
The B6 S4 is the first generation, and it was replaced in 2005 by the B7. The engine and performance were unchanged but the suspension was tweaked and in 2007 the Torsen centre diff updated. At the back, quad tailpipes made an appearance. Both generations have ventilated discs all round and speed-sensitive power steering. The latter feels quite natural but is slightly wasted on a car that is robbed of entertainment value by a quattro system that favours the front wheels over the rears. Again, it’s why that engine is the star of the show.
When you start looking for an S4, you’ll find that automatics outnumber manuals two to one, but hold out for a manual because it’s a slick set-up that also provides some extra, much needed driver engagement – plus it’s easier to play tunes with the engine. Wing mirrors are real alloy on early cars (check they’re not damaged because they’re expensive) and the seats are by Recaro. B7s added a Bose stereo. Saloons are most common, cabriolets are fun and Avants are as rare as hen’s teeth. Classic status beckons, so don’t hang around.
An expert’s view
Peter Macejka, Audi VW Specialist Centre: “The B6/B7 V8 is a good engine and sounds great, but it could do with more power. The 414bhp BS7 RS4, which uses a highly modified version of the S4’s 4.2-litre V8 engine, is more exciting. That car is a lot more expensive, though. The big problem with the S4 is the timing chain, or rather the plastic tensioner and guides, which break up after many heat cycles. In fact, we have an engine here on the bench being fitted with a new tensioner kit. The RS4 uses a steel tensioner and guides, so it’s not a problem. Another S4 weak spot is the rocker cover gasket. It goes brittle over time and allows oil to leak over the engine. It’s messy but easy to spot.”
Engine: With the engine started from cold, listen for timing chain rattles. Check the service history for regular oil changes, being wary of cars that have had extended service intervals. Inspect the oil level because it can fall due to either a failed PCV (positive crankcase ventilation) valve or, worse, scored cylinder walls. Misfires could be failing coil packs.
Power steering: Check the condition of the steering pump hoses, which run close to the engine and can develop leaks. A pump starved of fluid quickly destroys itself. It’s located at the back of the engine, so replacing it is not cheap.
Transmission: Cycle through manual or automatic gears, feeling for smooth, fuss-free changes. Clutch (it usually fails at around 100,000 miles), flywheel and torque converter problems are not unknown. Have the automatic transmission fluid changed immediately because it’s unlikely ever to have been refreshed. Get the rear diff oil changed, too.
Brakes and suspension: Check there’s ample life in discs and pads and that the handbrake holds. Listen and feel for knocks and bangs over rough surfaces.
Body: Corrosion lurks around front and rear wheel arches, so check for paint blistering. Look for body repairs, where rust can also develop.
Interior: Ensure the air-con works because the condensers can fail and repairs are expensive. Check the glovebox hinges aren’t broken. Buttons on the centre stack wear, as do side bolsters.
Also worth knowing
Before you buy, consider the running costs. Cars registered before 23 March 2006 attract road tax of £340, but after that date the charge rises to £600. Then there’s fuel economy, with owners reporting around 23mpg on a run but 18mpg on short drives.
How much to spend
£5500-£6999: Early private-sale B6 saloons, some with over 100,000 miles but also some lower-mileage ‘bargains’.
£7000-£8999: Mainly B7 saloons plus a sprinkling of cabrios and mileages around 80,000.
£9000-£10,999: Late (2009) B7 saloons, still with mileages around 80,000.
£11,000-£12,999: Some rare B7 Avants in immaculate condition.
One we found
Audi S4 4.2 Quattro, 2004, 62,000 miles, £5445: A low-mileage S4 manual being sold privately. It has an “almost full service history”. The exhaust is blowing slightly and there are some paint blisters. Make sure the chain is quiet from cold, chip the price by the cost of a full service and it could be worth a punt.