Audi A6

The CCWA 3.0 TDI rattles on cold start due to a pressureless chain tensioner. Chain drive C is most commonly affected and the most accessible repair point. Cost from 650 euros.

Symptoms: Metallic rattling immediately after a cold start for 1–5 seconds, sounds like loose metal clattering from the engine bay; disappears once oil pressure builds.

The CCWA 3.0 TFSI uses an Alusil cylinder block similar to the 3.2 FSI. When using Longlife oil (low HTHS values), the piston tends to tilt in the cylinder — engine damage risk.

Symptoms: Knocking/rattling noise from the engine, increased oil consumption, juddering under load, power loss.

The EGR system on the CCWA 3.0 TDI accumulates soot deposits, particularly in city use. EGR cooler leaks can cause coolant loss.

Symptoms: Engine warning light, power loss, rough idle, limp-home mode, occasional coolant loss from a leaking EGR cooler.

The oil heat exchanger (oil cooler) on the 3.0 TDI V6 develops leaks causing oil loss. An improved replacement unit is available as a retrofit kit.

Symptoms: Oil warning light, visible oil film under the car or in the engine bay, oil level dropping despite top-ups, oil smell after driving.

The dual-mass flywheel (DMF) on the CCWA wears at high mileages. Replacement is sensibly combined with a clutch change. DMF parts cost approximately 760 euros plus clutch.

Symptoms: Rattling at idle especially after a cold start, vibration when pulling away or changing gear, drivetrain droning.

On the CCWA 3.0 TFSI supercharger, all chains and tensioners were proactively replaced at 75,000 km. Timing chain wear is a known issue on this generation.

Symptoms: Rattling on cold start, sounds like a loose chain, disappears once oil pressure builds up.

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.