Models · Audi
Audi S4 B5 buying guide
The B5 S4 was built from 1997 to 2001 as a saloon and, from 1998, an Avant, with a 2.7 litre twin-turbo V6 and permanent quattro four-wheel drive. The engine block is strong, and most of what matters at a viewing sits around it: the turbos, the boost plumbing and the timing belt.
The versions
- 2.7 V6 biturbo (AGB), 265PS, with two BorgWarner K03 turbos and two intercoolers
- Permanent quattro four-wheel drive with a Torsen centre differential
- Saloon and Avant bodies
- 6-speed manual, with a 5-speed Tiptronic automatic offered in some markets
What to check on a B5 S4
3 model-specific things to look at when you view one. They're a starting point, not the full inspection.
Boost pressure and turbo noise
What to look for: On the test drive, once the engine is fully warm, accelerate hard in third gear. The car should pull strongly and evenly from around 2,000rpm. Listen for a loud siren-like whine, a hiss when you lift off, and look in the mirror for blue or white smoke.
Why it matters: Both small K03 turbos sit deep in the engine bay, and replacing them usually means taking the engine out, so their condition matters more than on most cars. Weak pull is just as often a split boost hose, a torn diverter valve diaphragm or a failed air flow sensor, which the engine reacts to by cutting boost. Those are inexpensive fixes, so a diagnostic scan and a boost leak test help tell the two apart.
Timing belt and water pump records
What to look for: Look in the history for an invoice naming the timing belt, with a date and mileage. The 2.7 V6 has a belt, not a chain. Specialists advise around five years or 120,000km at most, and the water pump is normally changed at the same time.
Why it matters: A belt that fails will cause serious engine damage. It's a long job on this engine because the front of the car is put into its service position to reach it, which is why most owners do the water pump and tensioners while it's apart. A car with a recent, invoiced belt change is a sign it's been looked after.
A rattle on cold start
What to look for: Start the engine from fully cold and listen at the front. A brief noise on start-up that disappears within a few seconds is common. A rattle that carries on beyond that is the thing to note.
Why it matters: Each cylinder head has a short chain linking its two camshafts, with a tensioner fitted with plastic pads. The pads wear with age and the rattle is the usual sign. The parts are inexpensive, and the work is often done together with the cam cover gaskets.
Also in the full guide
- Oil leaks from the cam covers
- The 1 to 2 gearchange
- Front suspension arms
- The cold start, test drive and paperwork checks for the exact version you're viewing
The full guide to the B5 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.