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Audi A6 common problems (2004-2011)

Audi A6

The Audi A6 Mk3 has always been an executive car for people who like to do things a little differently. So, it’s always had class-leading aerodynamics as part of its ethos, and where most rivals are rear-wheel drive, the A6 offers either front-wheel drive, or four-wheel drive, thanks to the Audi quattro system.

It not only offers a manual gearbox, but also a full-on automatic or a constantly variable transmission (CVT), which goes under the Multitronic name. And you can have an off-road version, called the A6 Allroad, which has jacked up air suspension and that quattro drive system.

It’s the sort of car that can cover a great many miles with no major problems, but it isn’t faultless. Issues have included whiny transmissions, faulty oil coolers and dodgy transmission selector mechanisms.

Still, that’s where Haynes comes in, because if you download our Haynes Autofix product for the A6 Mk3, we can help you to diagnose and repair lots of common problems, saving you loads of cash on garage labour charges in the process.

Audi A6

What recalls has the Audi A6 been subject to?

Airbags have been the source of some problems for A6 owners. Almost 6000 cars were recalled because the front airbags might deploy too late in a crash, while some cars were fettled because the curtain airbags might fail to go off altogether.

Then the passenger airbag was the source of another recall because the inflator could break when deployed, causing debris to be sprayed around the cabin.

Then 8468 cars with power-operated tailgates were recalled because the tailgate could suddenly close without warning.

A number of examples were recalled because foreign matter in the coolant could block the additional coolant pump, causing it to overheat.

Then 1073 cars were recalled because the fuel rails could spring a leak.

What common problems does the Audi A6 Mk3 have?

When you buy an Audi A6 Mk3, you expect to have a car that will make you feel good while it deals with the stresses and strains of daily motoring life, and which won’t let you down. And by and large, that’s what you’ll get. But that’s not to say it doesn’t suffer from the odd glitch.

For example, you might suddenly notice that the coolant in your car’s expansion reservoir has oil in it. This can be cause by a failure within the oil cooler that allows the two liquids to mix.

And it would be extremely annoying to get to the end of a journey and find that your A6 won’t allow you to remove your ignition key from the barrel. But that’s what some owners have suffered.

Some owners have also reported their Audi A6 suffering automatic transmission issues that cause the car to judder when pulling away and also to drop into limp-home mode.

The A6 quattro models are also known to have a problem that causes them to emit a whining noise between 30 and 40mph.

And an oil-pressure warning is going to cause a few heart flutters, so it’s best to sort that quickly.

Audi A6

Does the Audi A6 C6 have oil cooler problems?

The dreaded mayonnaise. You might have it on a sandwich but you definitely don’t want it in the important bits of your car.

But that can happen if you have an Audi A6. The issues lies with the oil cooler, which can suffer an internal failure, and allow oil and water to mix. And that is undeniably a bad thing.

To check, remove the thermostat and clean it out with proper cooling system cleaner. Then do the same with the expansion tank.

Then run the car for 30 miles, and check the system again. If there’s oil and water together, then you’ll need to replace the oil cooler itself.

And we can help you with the Haynes A6 Autofix product, which will guide you through the major steps.

Audi A6

Does the Audi A6 have ignition key problems?

This is going to be the ultimate frustration – dealing with the annoyances of a journey, and once you’ve got to the end you can’t get the key out of the ignition. What do you do? You can’t leave the car unattended because someone could drive away in it. Infuriating.

This is an issue that has afflicted numerous A6s fitted with an automatic transmission. The problem is that the transmission doesn’t recognise that the lever is in the P position. First, plug in a fault-code reader. If there are no codes, adjust the selector cable. If that doesn’t work, renew the gear detection switch. And if that doesn’t work, renew the selector mechanism.

Haynes A6 Autofix will be able to guide you through the intricacies of this procedure.

Audi A6

Does the Audi A6 have transmission problems?

A number of A6 Mk3 owners have reported an issue in which the vehicle judders when pulling away.

The cause is most likely that the automatic transmission fluid has become contaminated with coolant. This can occur in models with an ATF cooler integrated into the radiator.

If this has happened, the first course is to replace the radiator, which the Haynes A6 Autofix can guide you through.

Then you’ll need to replace the ATF filter and clean out all pipework. If that doesn’t work, you’ll also need to replace the automatic transmission, which A6 Autofix can also help you with.

Audi A6

Does the Audi A6 C6 have propshaft problems?

If your Audi A6 Mk3 has a quattro four-wheel-drive system, then this issue is a possibility.

When it occurs, you’ll notice a whining noise from underneath the vehicle as you drive at 30mph to 40mph on a cold day. So what’s causing it? It’s most likely the centre propshaft bearing on its way out.

You’ll need to raise the car and supporting it on axle stands, then unbolt the propshaft, before unbolting and renewing the centre bearing and refitting the propshaft to the vehicle.

One point of note – if you’re re-using the original propshaft, ensure that you mark its position next to the drive flange before you remove it from the vehicle. That way you can replace it in exactly the same position.

Audi A6

Does the Audi A6 have oil-pressure problems?

What’s that light? It wasn’t there before. ‘Bong’. Is that… an oil can? It is, and it can signal that your engine is suffering a drop in oil pressure. This is something you need to pull over and suss out straight away, because low oil pressure can be terminal.

However, the good news is that it generally isn’t something significant happening inside the engine. Instead, it’s more likely to be a faulty oil filter cover and faulty oil filter housing, which are allowing oil to leak out. You’ll need to replace the cover and housing, and it would be wise to change the oil at the same time.

This isn’t a big deal to fix, so as long as you allow your Haynes A6 Autofix to help you through the process, all will be well.