Audi S4
High-revving V8 naturally aspirated with direct injection, fitted in S4 B6/B7, RS4 B7, S5 B8 and R8. Timing chain sits on the gearbox side — repair requires engine removal. Oil change intervals of max. 10,000 km are mandatory. Short-trip use massively accelerates wear.
4.2 V8 in the B6 — the first eight-cylinder S4
Audi puts a V8 in the S4 for the first time — and nails it. High-revving to 8,250 rpm, with a manual it is a mechanical experience. The B6 sounds rawer and less refined than the later B7. Less polished, more visceral. The beginning of a short, glorious V8 era.
Engine Weaknesses 8
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
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 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
FSI direct injection without valve wetting leads to heavy deposits on the intake valves. Up to 40 hp loss on neglected vehicles. Only mechanical cleaning (BEDI) helps; fuel additives are ineffective.
Symptoms: Clear power loss, rough idle, poor cold-start behaviour, increased fuel consumption
The FSI high-pressure pump located in the engine valley can fail after 80,000–100,000 km. Starting problems and power drop result. Parts cost 500–900 €; installation is laborious.
Symptoms: Hard starting, power loss, jerking, occasional fuel smell in the engine bay
The water pump on the BBK fails after 120,000–140,000 km from bearing wear or defective seals. Overheating risk. More complex access on the V8 means higher costs than on smaller engines.
Symptoms: Coolant loss, temperature gauge rising, coolant smell, leak beneath the engine
Ignition coils on the BBK fail repeatedly; some owners report replacing a complete set multiple times within a few years. With a V8 there are 8 coils fitted; full replacement costs 300–700 €.
Symptoms: Misfires, jerking, rough idle, engine warning light with misfire fault codes
Timing chain cover gasket and camshaft seals develop leaks. Oil runs down the front of the engine and spreads over the underside. Engine removal often required for full resealing.
Symptoms: Oil spots under the vehicle, oil smell after driving, visible oil film on engine front face or underside
Vehicle Weaknesses 5
Rust forms at weld seams on the rear longitudinal members and at the rear subframe, as the zinc protection is worn away by stone chips. Structurally concerning on older vehicles.
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.
The V8 engine in the S4 B6 is known for frequent ignition coil failures. Several coils often fail in quick succession, leading to misfires and rough running.
The 1.7 tonne weight combined with the 344 hp V8 causes above-average wear on discs and pads. Brake discs are frequently due after 40,000–60,000 km.
The xenon headlights on the S4 B6 had faulty reflector coatings that reduced light output by up to 15% and increased the risk of dazzling oncoming drivers. Recall by Audi.