Audi RS6
The BSM is technically closely related to the Lamborghini V10 — the 5.0-litre V10 from the Gallardo was turbocharged to 580 PS for the RS6. Power delivery in everyday use feels broad and pushing, but the turbos dampen the high-revving character of the naturally aspirated unit. Ten cylinders in an estate produce a rumble no other family car offers. Thermally demanding: the turbos sit deep in the engine bay, intercoolers leak over time and then secondarily damage the turbos — the classic cascade. Oil pump seal wears early from engine heat. Every major job requires engine removal — diagnosis and repair become disproportionately expensive. Running costs are far beyond what the exterior suggests.
580 hp V10 BiTurbo estate — Lamborghini tech for family life
The C6 RS6 Avant is the most absurd family vehicle of its era: V10 with twin-turbo, related to the Gallardo block, in an estate with child seats. The Avant is the only true body style — the saloon is a footnote. The V10 sound is dampened by the turbos compared to the Gallardo naturally aspirated, but with an aftermarket exhaust it becomes a deep, bass-laden roar. Real-world consumption: 16 litres on the motorway, over 20 in town. Every lambda sensor requires engine removal. Those who accept that get a car that will never exist again.
Engine Weaknesses 6
The main problem of the 5.0 V10 BiTurbo: oil mist from the crankcase breather and EGR gases crack in the intake ports. Documented cases show power losses of over 60 hp.
Symptoms: Noticeable power loss, torque drop at higher rpm, rough running
The oil pump seal on the BSM wears under the extreme heat load in the engine bay. Oil seeps from the pump and collects under the engine. If ignored, oil starvation threatens bearing and turbocharger damage.
Symptoms: Oil patch under the vehicle in the oil pump area, falling oil level between services, oil smell in the engine bay at operating temperature.
A defective crankcase breather and worn piston rings lead to increased oil consumption on the 5.0 V10 BiTurbo. Normal consumption up to 250 ml/1,000 km; above 300 ml indicates a technical fault.
Symptoms: Dropping oil level, possible light blue smoke on overrun, oil mist around the intake area
All V6, V8, and V10 models in the A6 range eventually show timing chain problems. Early production years are more frequently affected. Chain repair on this engine is very involved.
Symptoms: Rattling on cold start, timing chain warning light, rough engine running
The wastegate linkages on both turbochargers tend to rattle on load changes. The high-pressure pump (Hitachi) also frequently causes problems. Turbo wear is higher on poorly maintained vehicles.
Symptoms: Rattling noise from engine bay on load changes, boost pressure drop at higher rpm
Recurring faults on the lambda sensors (bank 1 sensor 2 and bank 2 sensor 2) are a known issue on the V10. Loose connections on the throttle body and intake module can trigger similar symptoms.
Symptoms: Engine warning light (MIL), OBD lambda sensor fault, rough running, increased fuel consumption
Vehicle Weaknesses 14
The continuously variable Multitronic gearbox (01J/0AW) is considered the most serious weakness. Judder, rev fluctuations and complete failure. Early build years up to 2007 are particularly badly affected.
The A6 Allroad with adaptive air suspension frequently suffers from defective air spring bellows and overloaded compressors. Leaking bellows force the compressor to run continuously until it fails.
Blocked drain channels under the battery and sunroof allow water to enter the cabin. The comfort control module in the driver's footwell is damaged, leading to MMI total failure.
The Allroad with air suspension suffers from defective compressors and leaking air bellows. A leaking air bellows causes the compressor to run continuously until it overheats.
The Multitronic CVT tends to judder when pulling away, rpm fluctuations at partial load and, in the worst case, complete failure. All front-wheel-drive models are affected.
The high vehicle weight (up to two tonnes) accelerates wear of control arms, joints and anti-roll bar bushes. From around 150,000 km, extensive suspension work is virtually unavoidable.
Older A6 C6 examples show corrosion starting at the sills, door sill lower edges and tailgate. Where paint is damaged in the underbody area, corrosion progresses rapidly.
The cast-aluminium front control arms are prone to rubber bush wear. The long steel bolts in the wheel carrier corrode particularly badly and become extremely difficult to remove.
Pre-facelift vehicles (up to 2001) in particular show rust at the front wheel arches, door sill lower edges, and on the Avant at the roof edge above the windscreen.
Blocked drain holes under the battery lead to water ingress into the interior and can damage control units. Leaking cabin air filter housing seals exacerbate the problem.
The shaft seal between gearbox and propshaft on the A6 C5 eventually loses its seal. Gearbox oil drips onto the catalytic converter and burns off there. Often only diagnosed by smell or visual inspection from underneath.
The xenon headlights are susceptible to age-related failure. Bulbs and ballasts fail with increasing age. Rear lights absorb moisture through leaking seals.
The panoramic or sliding sunroof tends to leak, especially when the drain hoses are blocked. Result: water ingress into the interior.
The soft-touch coating on door handles, light switches and surrounds of the A6 C5 peels away at frequently touched spots, leaving a greasy surface. Almost all vehicles over 10 years old show this.