Audi S6 (C6/4F) 2006-2010

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If you want a 4 door vehicle which is the closest to a real sports car and which also requires sports car maintenance then choose the BMW M5 E60. If you want a more comfortable, more reliable fast car and you want to know who built your engine then choose the Mercedes E-class AMG W211.

But if you need a car which can go fast in bad, and worse weather and you can’t live without a V10 engine, then choose the Audi S6 C6. Of course there is also the RS6 which is, let’s be honest, a much better choice-in every way basically. Although we have to take into consideration that it is more expensive to buy, and in some places you can’t buy it at all-since the RS6 was not available everywhere in the World.

So moving back to the Audi S6 C6. This is a car for those people who want something more fascinating than the regular A6 C6 but at the same time they don’t want to attract much attention at the parking lot (or they can’t buy the RS6).

The exterior of the S6 is really not special at all, so until you start the engine and until you push the right pedal-until that nobody really gives a damn about your car. And actually, there are plenty of people who proudly stick the S6 badges and sometimes even the S6 front grill and bumper onto their regular diesel A6 (at least here in Eastern EU it’s a pretty common sight). Of course the fake badges surely give an additional 152 hp in some unbalanced parallel universe, but if you don’t want to be that guy who will ruin the universe, just buy the real S6 and the universe will be in balance.

Interior

The interior of this S6 is the same as in the regular A6 so the build quality is good and there are basically no issues with peeling plastic surfaces except the well-known windows control switch, the MMI center button surface or the keyless feature start stop buttons which can be occasionally worn. While the build quality is good, you have to keep in mind that nothing is perfect, which means, that because of the very stiff suspension you can sometimes hear various rattles from the dashboard on bad quality roads.

The only difference in the interior between the S6 and the regular A6 is that you can’t find a poorly equipped S6 since it already had numerous features as standard including: carbon interior trim, 2 zone automatic air conditioning with sun and humidity sensor, leather wrapped multifunctional steering wheel with shift paddles, interior light package, alcantara and leather combination or just completely leather seats, and let’s not forget the great electrically adjustable and heated front sport seats which are very supportive thanks to the big side bolsters. The only disadvantage of these side bolsters is that on the driver’s seat they can be more often more or less worn. But instead of the sport seats the previous owner could also choose the standard seats which are absolutely not supportive, but at least the side bolsters won’t be worn out on them.

Body, paintjob, rust protection

Believe it or not, you can unveil a lot by simply checking out the body of this A6. First of all check out the front of the car which can be misaligned. What I mean is, that the upper gaps around the front grill should be even on both sides and the gaps around the headlights should be even as well. If they are not even then the bumper and the headlights were removed in the past. This can indicate a smaller or a bigger frontal crash or they just removed these parts to fix something in this area, and after the fix they didn’t align these parts back correctly. In the picture below you can see that the gap next to the headlight is wider than on the other side, and the gap around the grill is also inconsistent mainly around the edges of the grill.


Then check out also all the visible screws on the front fenders and on the door hinges – all of them have to be intact. If you can see that the paint around the screws is damaged, then someone removed these parts in the past – again maybe because of an accident.

After this lets move onto the doors, because the doors in this car consist of two parts. The lower steel part and the upper aluminum door frame in which the window regulator assembly is mounted. Now, if someone had to readjust the door – again because of an accident, then he had to readjust this door frame as well. This is not the easiest thing and I have seen numerous examples when the door frame was not adjusted properly. But luckily you can check this very easily: the door has to be flush with the body, there has to be no gap around the upper seal, and if you press on the upper part of the door with your hand then it can’t make any creaking noises, which means that it has to sit firmly in the body.

Lastly, if you are buying the Avant version then it’s good to check the rear tailgate. The gaps on both sides have to be even and the tail lights have to sit evenly near each other. From the factory it’s always adjusted correctly so if the tailgate is misaligned, then it was removed in the past.

The rust protection of this car is mostly above average, but the road salt is a strong enemy and to top of that there are a couple of weak spots on the body:

-Specifically the lower parts of the doors can start to rust pretty easily but you usually won’t see this until the rust spreads pretty badly, since this part is hidden behind the lower door trims. So I would highly recommend to remove this trim on each door to find out if you got rust there or not.

-The next interesting place is the lower part of the front fenders next to the front doors. If you remove the front wheel well liner then you will most probably see a big amount of dirt in this area. You should definitely clean it, and at least put some wax to this place because if you let the dirt nicely sitting there then over time this area starts to rust. Who would imagine!

But if you want to continue to play this game of rust which you can’t see, then check out the place behind the rear wheels – specifically right behind the rear wheel well covers. Here you can in a lot of cases find rust as well.

And the last place which is more prone to rust is the tailgate of the Avant version, but actually the tailgate of the saloon can rust as well. So check properly mainly the edges of the tailgate and it’s also good to put some wax inside the tailgate since it usually starts to rust from the inside. At least the front hood and the front fenders are made from aluminum so there will be no rust on these panels.

Possible problems

Moving onto the possible problems unrelated to the drivetrain, they are again, the same as in the regular A6 so keep in mind that:

-the door locks, the window regulators or the keyless entry door handles can break more often

-the main front door speakers can rattle because of the loose plastic dust cap

the electronic steering lock can fail and can leave you stranded – you can find more information about this in THIS VIDEO I did

-then the seatbelt buckle can be faulty causing the seatbelt warning to not go off even if you are fastened

the air conditioning heater valve can be stuck which means that one side of the AC will blow cooler air than the other while the temperature is set to the same value on both side

-check also the electronic parking brake which can occasionally seize up mainly if the previous owner not used it regularly, so at least engage and disengage it a couple of times

+mainly on the saloon models there can be an issue with the tail light condensation/water leak. This can be fixed by either replacing the black seal which is on the plastic cover which is attached to the back of the light (on the picture below). Or if this wont help, then you can put silicone around the edges of the light-where the outer cover meets the plastic housing.

The Avant models can have leaking and later completely broken rear windscreen wiper motor so it’s good to check it. Then it’s also good to inspect the plastic washer fluid hose which goes from the front of the car to the trunk lid, because it can leak in two places. The first place is under the driver’s seat-here the hose can crack and fill this area. And the second place is near the left trunk lid hinge. The first leak is still not very known, but the second leak is well known and it should be already fixed in most of the cars, since if this leak is not fixed then the leaking washer fluid will ruin the expensive electronic modules in the trunk.

The water leaks into the interior are also not uncommon so make sure that the area under the windscreen is clean. There are 2 drain holes under the plastic scuttle cover which get clogged over time causing water leaks into the interior. + If the car is equipped with a sunroof then you should occasionally clean mainly the front sunroof water drains as well, since if they clog then you end up with water on the carpet.

Suspension

This S6 was available only with the regular coilover sport suspension. With this suspension the car sticks to the road pretty well but it’s also very stiff, so keep this in mind if you have bad quality roads around you.

Because of the stiff suspension the various components can be worn earlier than in the regular A6, so check all the control arms visually for cracks, check the shocks for leaks and listen for weird knocking or creaking sounds. Be prepared to replace the front control arm bushings on cars which have around 150 000 km (but this of course depends on if the car was used on good quality roads or not). + When it comes to handling, you can’t expect a sports car steering with plenty of feedback in this car, the steering is pretty numb without bigger feedback. So if you want a car with a precise sports car steering with great feedback then buy an M5.

Engine

This S6 was available with only the 5.2 l naturally aspirated V10 petrol engine. With 435 hp and 540 NM of torque it is definitely powerful enough. However the funny thing is, that at this day and age a lot of these engines don’t have this much power – mainly because of carbon build up, injectors or the because of the intake manifold. And these are basically the 3 main issues of this engine. On the other side if you are not like really used to a high performance car like this, then you won’t even notice that you missing for example 50 or 80 hp.

Main issues

-because of the direct injection you can expect carbon build up usually after 100 000 km which will cause loss of power and misfires

“To at least minimize the carbon build up I would recommend to: use only high quality premium fuel, change the engine oil after max 8 000 km, use the car on longer highway journeys, and after warming up dont be afraid to use the engine at high RPM”

-then of course the injectors can be faulty usually causing loss of power, but they can also leak. If they leak then they will slowly destroy the O2 sensors, and in the worst case the catalytic converters as well. By the way because of the lack of space you have to remove the engine to replace the O2 sensors, and by the way this car has 4 cats and 8 O2 sensors (in comparsion the RS6 has only 4 O2 sensors).

If you get fault codes for the Cats then remember that the O2 sensors are very sensitive, which means that your catalytic converter can be still in an acceptable condition even if you get a fault code for the insufficient performance of the Cat! + While in most cars only the O2 sensors before the cat affect the engine running, in this car even the O2 sensors behind the cats can be one of the reasons for poor running.

“Make sure that you are using only premium fuel in this car!”

-after this there is the complex variable intake manifold which will have sooner or later issues. Specifically the intake manifold inside center plastic flaps will get loose over time, and they can simply fall apart: this will cause loss of power, eventually fault codes with check engine light and misfires. Sometimes in the worst case the broken plastic bits can be sucked into the valves, or if you are like extremely unlucky then into the combustion chamber and cause bigger damage. All in all, you can expect play in the intake manifold flaps usually at around 100 000 km, so before buying it’s good to open the hood and check for a rattling noise from the intake manifold from 1000 up to 2000 RPM which indicates excessive play or broken bits in the intake manifold flap mechanism. (you can also use an endoscopic camera to check the inside of the intake manifold)

+ there are also the intake manifold front actuator motors which can fail but usually just in high mileage cars

As the engines in the regular A6, this V10 unit also has 4 camshaft adjustment solenoids which can leak oil because of the faulty o-ring on them or they can get stuck usually because of long oil change intervals.

Oil leaks

You should be also prepared that the engine can leak oil, mostly from the usual spots like the:

-valve cover gaskets – (which you can replace easily)

-the oil pan, the front crankshaft seal

-or the oil filter housing (The o-rings on the bottom of the oil filter housing can leak causing the oil to accumulate under the intake manifold-between the cylinder heads, and then it will leak out from the front of the engine)

But also from not that usual placesmostly in higher mileage cars like:

-the rear timing chain covers

-the spark plug tube seals

To fix the rear timing chain cover leak you have to remove the engine – this is not very nice but it’s still understandable since there is no space behind the engine.

However to fix the leaking spark plug tube seals you have to remove the engine as well, and why? Well because this is not the valve cover gasket leaking, this is a separate gasket for the park plug tubes only. This gasket is located one floor below the valve covers, specifically under a frame which is bolted to the cylinder head and it’s also connected to the rear timing chain cover. The camshafts are under this frame as well and since the timing chain is at the end of the camshafts then you can’t move the camshafts, because they are under tension of the timing chain. A little complicated, but all you have to know is that the leaking spark plug tube seals will cause the oil to leak onto the spark plugs (later causing misfires), and the only way to replace these seals on both sides is to remove the engine.

“You have to remove the engine if you want to replace also the: power steering pump, AC compressor or the starter motor.”

Other funny stuff

The high pressure fuel pumps can be faulty and they can leak, so keep extra money for them as well. (faulty HPFP: loss of power, leak)

And lastly, there is a bigger bonus issue which is not like very common to be fair, but it’s still worth to mention it. It’s the excessive oil consumption which can be caused by the damaged cylinder walls. There are cases when the engine block was replaced because of this, but mostly just on cars made to 2008. However as I said this is not extremely common so there is no need to panic yet. A reasonable amount of oil consumption is acceptable, which means that if the engine takes 1L of oil for 7000-8000 km then you can remain calm.

The engine misfire is a pretty common problem on these cars. Sometimes the owners don’t have bigger issues finding them, but sometimes they replace so many parts that at the end they will wake up and say: fuck it I can’t stand it anymore and they just sell the car (based on a true story, actually more than one true story…)

So the misfires can be caused by basically anything – usually spark plugs or ignition coils but also because of faulty injectors, faulty intake manifold, faulty PCV, vacuum leaks, carbon build up, bad O2 sensors, high pressure fuel pumps, regular low pressure fuel pump, and sometimes if you are really lucky – it’s enough to clean the ignition coil connectors on the wiring harness or replace the plastic ignition coil connector tube which can be loose (the connector can back off causing a misfire if the connector tabs are broken)

+ as a bonus (I like bonuses) there are also cases when the engine had misfire because of a bent valve which was caused by the loose intake manifold plastic part which broke off and which was sucked into the valve and jammed it (so in the worst case even this kind of a chain reaction is possible)

Vaccum leaks

Keep in mind that the there are also many different plastic and rubber vacuum and pcv hoses which wil over time (and because of the excessive heat from the engine) crack and cause vacuum leaks. By the way the intake manifold itself can cause vacuum leaks too.

+ It’s good to replace the accessory belt and the pulleys on cars which have more than 150 000 km as a preventive maintenance.

Lastly, it’s important to:

-check all the fluid levels before buying

-check the coolant: it has to be topped up, clean and pink without any oil smell or oil traces

-start the car when it’s cold and check for an uneven idle or shaking which indicates misfires, the engine has to run smoothly all the time

This V10 engine is equipped with timing chains which are not known for being prematurely worn, but of course as usual check for a short rattling noise at cold start which will indicate worn tensioners or stretched chain.

Transmissions

The 6 speed automatic transmission in this car is not known for being weak or for having extraordinary issues, so just check if it’s shifting smoothly without shuddering and hesitation and change the oil in it regularly.

The simple Quattro 4WD system is great and reliable even in high mileage cars, although it’s of course good to occasionally change the oil in the front and rear differentials + it’s also good to check for vibrations or shuddering at hard acceleration from stand still which can indicate worn prop shaft.

To summarize things up: buy only a car with proper maintenance history ideally from the first owner, find a good independent mechanic if you can’t work on the car yourself, and keep at least 5 000 € for the additional repairs. However if you are buying a car which doesn’t have at least the basic things replaced like the intake manifold or injectors then you should keep at least 8 000 €. Or buy an RS6 instead if you can.

Now you can ask: OK, but isn’t the RS6 even more complicated and more unreliable? Well, yes and no:

The engine in the RS6 has 2 turbochargers, so it is indeed a bit more complicated. However it doesn’t have that complex variable intake manifold, it is not known for having issues with worn cylinder walls, and the turbochargers (with the proper care) can withstand a lot more than the variable intake manifold in the S6. The thing is, that sooner or later you will have to remove the engine from the RS6 as well-mostly because of the oil leaks and because of the parts which are simply not accessible with the engine in place. But at the end of the day you will still have a much more powerful, a more rare, and a more fun car than the S6.

And if you have personal experience with this S6, or more information about it, then you can write it into comments!

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