Audi RS4
The CFSA is Audi's farewell gift from the naturally aspirated V8 — 8,250 rpm rated speed, 450 PS without a turbo. The character is the opposite of a BiTurbo: the engine demands revs and rewards with a sound no production family car offers any more. Double throttle body in the intake: soft down low, sharp up top. Direct injection (FSI) is the structural weakness: without fuel washing over the intake valves, their backs coke up from blow-by oil vapour. Walnut blasting every 50,000–70,000 km is mandatory. The variable intake manifold with flaps tends to rattle from oil deposits — bolts can come loose and fall into the engine. Timing chain fundamentally robust, needs clean oil and short change intervals.
RS4 B8 — NA V8 in a wagon, the last of its kind
450 hp naturally aspirated V8 at 8,250 rpm in a wagon. After the B7, the second and last generation with a high-revving V8. Heavier and less raw than the B7, more liveable in return. The auto fits better than expected — shift speed makes the loss of the manual bearable.
Engine Weaknesses 9
CFSA uses simplex chains on the gearbox side. Although more robust than the BBK predecessor, tensioners and guides are wear items. Engine removal mandatory for a full repair. Significantly more durable with regular short oil change intervals.
Symptoms: Rattle on cold start, timing chain noise at low revs, engine warning light
The CFSA revs to 8,250 rpm as a high-revving naturally-aspirated engine. Con rod bearings are under extreme stress. Neglected oil changes or poor-quality oil risk bearing wear. Preventive replacement at 80,000–100,000 km is discussed.
Symptoms: Knocking from the engine at operating temperature, increasingly loud rumbling at high revs, oil pressure drop
Four camshaft adjusters on the CFSA are more heavily stressed by high-rev operation up to 8,250 rpm than a normal V8. Oil quality and short change intervals are critical for longevity.
Symptoms: Rattle on start, camshaft fault codes, limp mode
The flaps in the variable intake manifold stick due to oil deposits from crankcase ventilation and begin to rattle. In the worst case screws or flap fragments come loose and are ingested by the engine — piston and valve damage can result.
Symptoms: Rattling or clattering from the intake area at idle and low revs, rough idle, individual cylinder misfires.
FSI deposits on intake valves documented from as early as 32,000 km, especially severe with urban use. Walnut blasting costs 600–900 € for RS4/RS5. Regular cleaning every 40,000–60,000 km recommended.
Symptoms: Power loss (up to 40 hp), rough idle, poor throttle response at low revs
RS4/RS5 with CFSA shows elevated oil consumption due to high revs and spirited use. Valve stem seals and piston rings wear. 1–2 L/1,000 km during spirited driving is normal.
Symptoms: Oil level drops noticeably, slight blue smoke after full-throttle sections, oil consumption above 1 L/1,000 km
CFSA water pump is heavily stressed in RS4/RS5 high-performance use. Failure after 100,000–140,000 km. Replace thermostat at the same time. Tight engine bay in the RS4 B8 means higher labour costs.
Symptoms: Coolant level drops, temperature fluctuations, coolant smell after driving
The FSI high-pressure pump in the CFSA can fail after 80,000–100,000 km. In the RS4/RS5 with high-performance demands this is particularly critical. Expensive replacement due to cramped engine bay.
Symptoms: Starting problems, severe power loss, hesitation under load, fuel smell
8 ignition coils in the CFSA are particularly prone to failure due to high-rev use. Motorsport-oriented use increases wear. Complete coil replacement 300–700 €.
Symptoms: Misfires, engine warning light with misfire code, hesitation on acceleration
Vehicle Weaknesses 19
The 7-speed dual-clutch gearbox DL501 is prone to mechatronics failures. Typical: judder on pull-away, delayed gear changes or complete failure. Repair costs €3,000–5,000, a new unit up to €11,000.
The optional Dynamic Ride Control hydraulic system is known for leaking dampers from ~80,000 km. Control valves rattle, dampers lose oil pressure. Repair requires dealer-level special tooling.
The optional rear sport differential can fail after 80,000–100,000 km. A repair bill of over €3,000 is then to be expected. Regular oil changes extend service life.
At higher mileage, wishbone rubber bushes and ball joints wear out. Typical creaking when driving over uneven surfaces. A complete wishbone set including fitting costs €1,200–1,500.
The optional adaptive suspension is prone to damper failures from around 120,000 km. Affected dampers fail when hot. A single adaptive damper costs €500 net; a complete front replacement around €2,200.
On the optional sport differential, grease/oil leaks from the propshaft. Cause: the end-cap bonding fails to hold the internal pressure (TPI 2025572/1). Repair requires gearbox removal.
The rear subframe and axle carriers rust under the plastic covers where dirt and moisture accumulate. Severely affected carriers require replacement.
MMI system fails — screen black, no audio or permanent reboot loops. Cause is often water damage to the Bluetooth control unit in the footwell or overvoltage during a battery change.
On the optional panoramic roof, the drain spouts in the wheel arches become blocked or detach. Water runs into the interior rather than away — headlining and rear wheel arch get wet.
The AC compressor on the B8 has no magnetic clutch and is electronically regulated. With increasing mileage the control unit or the compressor itself fails — frequently after 100,000–150,000 km.
Control units (including Bluetooth module, interior surveillance, hands-free phone kit) fail to enter sleep mode properly and create excessive quiescent current draw. Battery flat after short periods of standing.
Rust forms on the wheel arch edges of front and rear wings. Inadequate factory cavity protection promotes corrosion — on early models Audi replaced wings under goodwill.
The optional ceramic brake discs last very long but are extremely expensive to replace. A complete set including calipers runs into four to low five figures.
The large brakes on the S4 B8 wear quickly under spirited driving. A complete front-and-rear brake disc set in OEM quality costs around €1,400.
From build year 2008, door seals detach from the adhesive in places — a well-known early issue on the B8. Moisture ingress increases and wind noise worsens. Audi replaced seals under goodwill on early cars.
The xenon ballast in the headlight fails due to moisture ingress or ageing. Affects the standard Bi-Xenon headlights — one headlight sporadically goes out or flickers.
The universal joint in the steering column or the electric power steering pump produces clicking or grinding noises during slow steering inputs and manoeuvring. Particularly noticeable during temperature swings.
Under spirited driving the steel brake discs wear above average. Rear axle often due from ~50,000 km. Brake work on the RS4 B8 is noticeably more expensive than on standard models due to the size.
The MMI infotainment system shows occasional failures and freezing on older model years. Bluetooth issues and navigation failures are known and often fixable via updates.