The C6 (2004-2011) and C7 (2011-2018) Audi A6 each have a short list of known faults. On the C6, the usual suspects are coolant getting into the automatic gearbox, an oil cooler that mixes oil and water, a worn centre propshaft bearing on quattro cars and a key that will not come out of the ignition. On the C7, most of what you need to know is in its recall history: the 2.0 TFSI electric coolant pump and several fuel-leak campaigns on petrol cars.
Each of these is a known part with a known fix, and many of them can be put right with a tested used part rather than a new one from a dealer. If you already know what you need, browse our Audi A6 spares.
Key Takeaways
| Question | Quick Answer |
|---|---|
| Which A6 generations does this cover? | The C6 (2004-2011) and the C7 (2011-2018). |
| Why does my A6 judder when pulling away? | On the C6, Haynes says the most likely cause is automatic gearbox fluid contaminated with coolant, on cars with an ATF cooler built into the radiator. |
| What is the "mayonnaise" in my coolant tank? | Oil mixing with coolant, which Haynes links to an internal failure of the oil cooler. |
| Is there a known C7 coolant pump problem? | Yes. In the US, 2012-2015 A6s with the 2.0 TFSI were recalled twice for an electric coolant pump that could overheat. |
| What does a used A6 gearbox or engine cost? | Our price guide puts used A6 gearboxes at about R4,500 to R25,000 and used A6 engines at about R25,000 to R65,000. |
First, Know Which A6 You Have
The C6 A6 ran from 2004 to 2011. Haynes notes that alongside a manual gearbox it was offered with either a conventional automatic or the multitronic CVT, so an automatic C6 can have either - check the gearbox code before you buy.
Source: Haynes - Audi A6 common problems (2004-2011)
The C7 A6 went into production in 2011 and was facelifted in late 2014. In South Africa, the front-wheel-drive 2.0 TDI and 2.0T FSI were launched in 2011 paired with an eight-speed multitronic.
Source: IOL Personal Finance - Audi A6 now more attainable (2011)
At the 2014 facelift, Audi replaced the multitronic on front-wheel-drive versions with a newly developed seven-speed S tronic dual-clutch gearbox.
Source: Audi press release - The new Audi A6 and A6 Avant (September 2014, archived)
That matters when you go looking for parts. "A6 gearbox" can mean a CVT, a dual-clutch or a torque-converter automatic depending on the year, engine and drive, so always quote the gearbox code or your VIN. Our DSG and S tronic gearbox guide explains how the dual-clutch boxes differ.
Judder When Pulling Away and Limp Mode (C6 Automatic)
Some C6 owners have reported the car juddering as it pulls away and the gearbox dropping into limp-home mode. Haynes says the most likely cause is automatic transmission fluid that has become contaminated with coolant, which can happen on cars with an ATF cooler integrated into the radiator. The first step is a new radiator, then a new ATF filter and cleaned-out pipework. If that does not cure it, the gearbox itself has to be replaced.
Source: Haynes - Audi A6 common problems (2004-2011)
Act on it early. Haynes' fix starts with the radiator and only ends with the gearbox if that fails. If the gearbox has already gone, a tested used unit is usually the economic answer - see our used Audi gearboxes and match the code before you buy. Multitronic owners will also want our multitronic variator repair guide, which covers the CVT itself.
Oil in the Coolant: Oil Cooler Failure (C6)
If you open the expansion tank and find a creamy, mayonnaise-like sludge, oil and coolant are mixing. Haynes links this on the C6 A6 to the oil cooler suffering an internal failure. Its suggested check is to remove the thermostat and clean it out with a proper cooling-system cleaner, do the same with the expansion tank, drive about 50 km (30 miles) and look again. If oil and water are mixing again, the oil cooler has to be replaced.
Source: Haynes - Audi A6 common problems (2004-2011)
On this car Haynes names the oil cooler as the cause, so have it checked before anyone quotes for a head gasket.
Key Stuck in the Ignition (C6 Automatic)
A frustrating C6 fault: you park, select P, and the key will not come out of the barrel. Haynes explains that the gearbox does not recognise that the lever is in P. The fix runs from cheapest to dearest - read the fault codes, adjust the selector cable, replace the gear detection switch, and only then replace the selector mechanism.
Source: Haynes - Audi A6 common problems (2004-2011)
A Whine at 50-65 km/h on Quattro Cars
On a C6 quattro, a whining noise from underneath at around 30-40 mph (roughly 50-65 km/h) on a cold day is most likely the centre propshaft bearing on its way out. The repair is to support the car, unbolt the propshaft and replace the centre bearing. Haynes adds one tip worth repeating: mark the propshaft's position against the drive flange before you remove it, so it goes back in exactly the same place.
Source: Haynes - Audi A6 common problems (2004-2011)
Oil Pressure Warning: Check the Oil Filter Housing
An oil pressure warning should always stop the car, because low oil pressure can destroy an engine. On the C6, though, Haynes says the cause is more often a faulty oil filter cover and oil filter housing letting oil leak out than a problem deep inside the engine. Replace the cover and housing and change the oil at the same time.
Source: Haynes - Audi A6 common problems (2004-2011)
C7 2.0 TFSI: The Electric Coolant Pump Recalls
US-market 2012-2015 A6s with the 2.0 TFSI (a specific EA888 version, according to the recall report) have an electric coolant pump that was the subject of two US safety recalls. Under NHTSA campaign 17V002000, the pump could be blocked by debris from the cooling system and overheat, which can increase the risk of a fire. Dealers updated the software so that power to a blocked pump is cut. The follow-up campaign 18V229000 found the pump could also short-circuit from moisture inside it, and dealers replaced the pumps.
Source: NHTSA - Part 573 safety recall report 18V229
These are US campaigns, and a South African car's recall status depends on its own VIN. On any 2.0 TFSI C7, ask an Audi dealer whether open campaigns exist for that car, and treat unexplained coolant loss or a coolant warning as urgent. Our Audi cooling system parts cover radiators, pumps and thermostats.
C7 Petrol Cars: Fuel-Leak Recalls
Several US campaigns on petrol C7 A6s involve fuel leaks, each of which can increase the risk of a fire:
- 15V019000 - 2012 A6: the fuel injection system may leak; dealers replaced the fuel rails and seals.
- 16V646000 - 2012-2013 A6 and A7: a fuel hose in the engine bay may degrade and leak; dealers replaced the under-bonnet fuel pump and fuel hose.
- 17V781000 - 2012-2014 A6 and A7: a fuel line has a compression point that can weaken and leak; dealers replaced the fuel line.
- 19V035000 - 2016-2018 A6, A7 and Q7 (and 2015-2018 A8): the left and right fuel rails may leak; dealers replaced both rails.
Source: NHTSA recall data - 2012 Audi A6 and 2016 Audi A6
A smell of petrol in or around a petrol A6 is never something to drive on. As with the coolant pump, confirm the recall status of your own car by VIN.
C7 3.0 TFSI: Carbon on the Intake Valves
The supercharged 3.0 TFSI is direct-injected, so fuel is sprayed into the cylinder instead of over the intake valves. Without that washing effect, carbon builds up on the valves over time, which can cause misfires, a rough idle and a loss of power. Independent specialists typically remove it by walnut-shell blasting.
Source: Euro Auto Pro - Common problems of the Audi A6 C7 3.0 TFSI
Source: Foreign Automotive - Audi 3.0T supercharger problems
If a C7 3.0 TFSI runs rough at idle with misfire codes and the coils and plugs check out, carbon build-up belongs on the list before anything more expensive.
Airbag Recalls Worth Checking
NHTSA campaign 18V370000 covers 2012-2018 A6 sedans with basic front seats. Wear of the sensing mat in the front passenger seat can make the occupant detection module malfunction, so the passenger airbag may not deploy properly in a crash. Dealers fitted a repair kit.
Source: NHTSA recall data - 2014 Audi A6
For the C6, campaign 18V427000 covers 2005-2011 A6 sedans and 2006-2011 A6 Avants with passenger front airbag inflators that may explode in a crash because the propellant degrades after long exposure to humidity and temperature cycling. Dealers replaced the passenger front airbag.
Source: NHTSA recall data - 2010 Audi A6
An airbag warning light on a used A6 is a reason to ask questions before you buy, not after.
What Used A6 Gearboxes and Engines Cost
The two big-ticket A6 repairs are the gearbox and the engine, and those are where a tested used unit saves the most.
| A6 Part | Indicative Used Price (our 2025 price guide) |
|---|---|
| Used A6 gearbox (manual, multitronic or Tiptronic) | R4,500 - R25,000 |
| Used A6 engine (e.g. 2.0 TFSI, 3.0 TDI) | R25,000 - R65,000 |
These are indicative figures, so ask us for a current quote. Where your car lands in those ranges depends on the gearbox or engine code, the mileage and whether it is a front-wheel-drive or quattro unit. For engines, see our used Audi engines and always buy a compression-tested unit whose code matches your car.
Buying a Used A6: The Five-Minute Check
- Open the coolant expansion tank. Creamy sludge points at the oil cooler.
- Pull away gently from a standstill a few times. Judder on an automatic C6 needs explaining before you pay.
- Select P and take the key out. If it sticks, budget for the selector fix.
- Drive a quattro at 50-65 km/h with the radio off. A whine from underneath is most likely the centre propshaft bearing.
- Ask for the recall history by VIN on any C7, especially a 2.0 TFSI or a petrol C7 from 2012-2014 or 2016-2018.
A car that fails one of these is not necessarily a bad buy. It is a negotiating point, provided you know what the part costs to replace.
Related Reading
- Audi Q7 common problems - the same treatment for the 4L and 4M Q7, which shares the quattro propshaft bearing issue
- Audi DPF and EGR problems on TDI diesels - what goes wrong on 2.0 and 3.0 TDI A6s
- Contact Audi Parts SA - send your VIN and we will confirm the exact part for your A6
