Audi S4 B6
Weaknesses, engine ratings and buying advice
The Audi S4 B6 (2003–2005) — BBK (4.2 V8, 344 hp). Emotional but expensive to maintain.
Timing chain: rattles from 80,000–120,000 km, full revision up to €7,500. Alusil bore surface degrades. Auxiliary coolers wear.
2026 market: From ,600–9,900 (high risk), with chain revision ,200–18,700. Insider pick: Only buy with chain revision proof.
Body Variants
The Audi S4 B6 is available as Sedan and Avant and Convertible — choose your body type for specific insurance data:
Generations
Engine Overview
The Audi S4 B6 is available with one engine variant at 344 hp.
4.2 V8 FSI with 253 kW — full aluminium, 4 overhead camshafts, 4 timing chains, Nikasil cylinder coating, direct injection. THE main problem: all 4 timing chains, guide rails and tensioners tend to stretch. Probable from 100,000 km, sometimes from 60,000 km. Engine must come out completely, 25 hours labour — cost €7,000–9,400. Often more than residual value. Second major issue: Nikasil cylinder coating reacts with sulphur-containing oil — coating deteriorates progressively, oil consumption rises to seizure. Use only low-SAPS oil. Intake valve coking from FSI from 80,000 km (cleaning from €1,000). Not replacing timing chains = Russian roulette. The only reason for the S4 B6: V8 sound that is unmistakable at full throttle.
- !! Timing chain: tensioners and guide rails — THE main problem from 80,000 km
Chain tensioners and guide rails on the BBK wear prematurely, often from 60,000 km. Chain skips teeth → engine damage. Complete engine removal required; gearbox must be separated. Costs: 2,600–7,500 €.
Symptoms: Metallic rattling on cold start, progressively louder ticking at operating temperature, engine warning light, sudden power loss - !! Alusil cylinder bore wears — elevated oil consumption to engine failure from 120,000 km
The BBK uses Alusil-coated aluminium cylinders (not Nikasil). With sulphur-containing oil or long intervals the bore surface is damaged. Oil consumption rises to up to 4 L/1,000 km; result: piston seizure. Engine block replacement ~10,000 €.
Symptoms: Rapidly increasing oil consumption, blue smoke, falling compression, borescope reveals bore damage - !! Camshaft adjusters generate fault codes — limp home from 70,000 km
Camshaft adjusters on the BBK wear and generate camshaft deviation fault codes. Vehicle goes into limp-home mode. Adjuster replacement possible without engine removal; tensioners/rails require engine removal.
Symptoms: Rattling on start, engine warning light, limp-home mode, reduced engine output, rough idle
+ 5 more engine weaknesses + vehicle weaknesses
Vehicle Weaknesses
| Weakness | Cost | |
|---|---|---|
| Control arms and ball joints wear The front control arms wear accelerated by the S4's high weight. Ball joint play is a typical MOT failure point. Full replacement often required at 200,000 km. Symptoms: Knocking and banging over surface irregularities, unsettled handling, steering flutter from 150,000 km | Medium |
Top Reported Issues
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Known Problems and Issues +
A total of 13 weaknesses have been documented for the Audi S4 B6 (2003–2006) — 8 engine-related and 5 vehicle-related. One problem engine: BBK (4.2L V8 FSI). Typical issues affect Suspension, Rust, Brakes, Electronics.
What to watch out for with the Audi S4? See the detailed listing of all engine and vehicle weaknesses in the sections above.
Frequently Asked Questions
What problems and weaknesses does the Audi S4 B6 have? +
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Last updated: February 2026 · All information without guarantee