Audi A6 C6 came on the market in 2004 when it replaced the previous Audi A6 C5. This is the third generation of this model. In 2008 it underwent a restyling that brought changes to the design and some modernizations on a technical level and in the interior. It was produced until 2011 when it was replaced by the new generation Audi A6 C7. Let’s see the Audi A6 C6 review with the most important information, faults and common problems.
Table of Contents
- Impressions and Description
- Reliability and Issues
- Engines and their Problems
- Conclusions and Advice & Tips for buying used
Impressions, Interior and Comfort
Audi A6 C6 is a very popular high-end car on the used market. It is a car that has a lot to offer despite its age. Those in good condition sell easily and quickly. As already mentioned, it was produced from 2004 to 2011 and in the years between 2005 and 2007 it was the best-selling model in the class with more than 120,000 copies per year. In 2005 it received the “World Car of the Year” award.
Audi A6 C6 is a competitor to such German cars as BMW 5 Series E60 and Mercedes E-Class W211. Nowadays it can be found at a relatively low price. This fact makes it available for purchase for many people with limited budgets, but not everyone is aware that even if the purchase price is relatively low, maintenance and repair costs are always big for a premium car.
Later we will see if the maintenance costs will not be exaggerated to use a similar car. We advise not to save money during the purchase and look for a car in good condition by following our advice.
Platform and Body
The platform is traditional for this German manufacturer: with a longitudinally installed engine and with front-wheel drive. It was optionally possible to mount the Quattro all-wheel drive system.
The front suspensions are with high quadrilateral with virtual steering axis in aluminum. The rear suspension is multilink with lower trapeze. Optionally, air suspension could be installed.
The body design of the Audi A6 C6 is basically an evolution of the style that was already on the previous generation. Aesthetically, the car has become much more modern and youthful. Despite its great age, the model is still current and does not give the feeling of old age. Here the famous single-frame grille appeared for the first time. After the restyling the situation has improved further, the new headlights and taillights are particularly noticeable.
Audi RS6 (C6)
Aesthetically, the car is attractive, both before and after the restyling, especially in the more equipped versions.
The third generation Audi A6 is available in two body styles: sedan (4-door) and Avant (station wagon). The German car has a length of 4916 mm, a width of 1855 mm and a height of 1459 mm. The wheelbase is 2843 mm. The weight of the car varies from 1445 to 1950 kg depending on the version.
In addition to the classic versions, there are also the sporty Audi S6 and RS6 versions. Both are different aesthetically, they are wider and more aggressive. Both were fitted with V10 engines: on the S6 a 435 hp 5.2-litre V10, on the RS6 a 5.0-litre V10 and 580 hp.
There is also a dedicated off-road version called Audi A6 Allroad, based on the Avant.
Comfort and Practicality
After moving the engine in front of the front axle (and not behind as for example on the BMW 5 Series E60) the interior space has significantly increased. On the front seats anyone will be able to position themselves comfortably, rear passengers will also be comfortable if they are not particularly tall.
The Audi A6 C6 has the largest trunk/boot in its class – 545 liters on the sedan and 565 liters on the station wagon (expandable up to 1660 liters by folding the rear sofa). Both BMW and Mercedes perform worse in this respect. The boot has a comfortable shape, the full-sized spare wheel and the battery are located under the floor.
The suspensions offer a good compromise between softness and stability on the road. On roads in good condition you won’t feel any discomfort. Ride comfort is very good. All together it makes the Audi A6 C6 an enjoyable car both in and out of town. You can find an Audi A6 C6 with air suspension which improves the situation even more.
Interior and Equipment
One word can be used to characterize the interior organization of the Audi A6 C6 – outstanding! The interior has a modern and welcoming style. The central panel is oriented towards the driver. The quality of the materials used is very high and they are assembled in the best possible way. Even after many years the various buttons are still tactile, visually beautiful and function well. But that’s no wonder, for a car of this class this is normal. A car in good condition will only give satisfaction and a lot of driving pleasure.
On some elements, serious signs of wear may appear at high mileage. First of all, of course, the most used elements wear out: the steering wheel trim and its buttons, the gear knob, the climate control buttons, multimedia buttons and more. At high mileages, wear and tear on the seat upholstery is also unavoidable.
The good part is that all traces of wear and tear present in the cabin can be eliminated if desired. Some pieces can be replaced, others can be repainted or restored.
Some owners of the Audi A6 C6 say that the soundproofing has deteriorated compared to the previous generation. But these are subjective opinions and in any case, the soundproofing is very good here too. Also, on cars with diesel engines there is better soundproofing in the engine area. This is to compensate for the higher noise level of diesel engines compared to petrol ones.
Usually the car is very well equipped with various useful systems. This is possible thanks to the complex electronic system inside. Even the poorest cars have everything you need for daily use. On the most equipped cars it is not uncommon to find automatic climate control, comfortable leather seats with heating, a multifunctional steering wheel, an automatic gearbox, a good multimedia system and much more.
Audi A6 C6 has a sophisticated multimedia system with good quality audio. The multimedia system MMI (Multi Media Interface) allows you to combine the control of radio, navigation, climate control and other electronic systems.
Safety
In the EuroNCAP safety test, the Audi A6 C6 got 5 out of 5 stars. Crash safety is quite good, but to decrease the risk you need good tyres. Tires are almost the most important thing for safety on the road.
Reliability and Issues
Gearbox and Transmission
The Audi A6 C6 could be fitted with the manual gearbox, the classic Tiptronic automatic gearbox and the Multitronic CVT (continuously variable transmission).
Manual transmission
The manual gearbox has no particular problems and is quite durable. However, the dual-mass flywheel is not very long-lived and sooner or later it will have to be repaired or changed. The price is quite high.
With powerful engines, at high mileage, wear of the second and third gear synchronizers can be noted.
Multitronic CVT (continuously variable transmission)
Continuously variable automatic transmissions must be checked very carefully. The Multitronic CVT can only be found on the Audi A6 C6 with front-wheel drive. Different versions of the Multitronic can be mounted here: VL-300 (01J), VL-380 (0AN) and VL-381 (0AW).
The Multitronic is very pleasant when it works well, but it is a particular type of gearbox that needs attention and docile use. If used incorrectly, problems can start as early as 100,000 km (60 k miles). The CVT does not like skidding, aggressive starts, shock loads, towing heavy trailers and driving at maximum speed. With calm use, the Multitronic can last even more than 200,000 km (125 k miles) without fatal breakdowns (some cars reach up to 220 – 260,000 km or 135 – 160 k miles).
Among the main mechanical weak points we have the cones and the chain. The chain has an average life of about 180 – 250 thousand km (110 – 155 k miles). It really depends on the style of use and the frequency of services. Cones can be damaged if you are late replacing worn chain or if you tow the car. In fact, the Audi A6 C6 equipped with the Multitronic CVT cannot be towed for long distances (it can only handle movements of a few metres). Replacing the chain is not very expensive and it is certainly better to replace this element in time than to repair the whole gearbox.
From the point of view of electronics, failures of the control block can happen, which is located directly on the gearbox body and heats up together with it. Consequently, in case of high operating temperatures, the failure of the control board and speed sensors is quite likely. In some cases it is possible to repair, in others it is necessary to replace these expensive elements.
Otherwise minor faults, malfunctions and failures are missing. This is a typical feature of these automatic gearboxes, they do not give any problems or signs of wear until they wear out completely. To increase the life of this gearbox, it is important to change the oil at least every 50,000 km or 30 k miles (better to anticipate 30,000 km or 20 k miles if the car is used mainly in town and in heavy traffic). At each oil change, it is necessary to check whether there are any fragments that indicate the wear of the pump. The pump and solenoids can fail due to overheating or very dirty oil. Precisely for this reason, in addition to regular oil changes, you need to keep an eye on the cooling system and in particular the thermostat which can get blocked.
Early production Multitronic gearboxes were more sensitive and had a higher likelihood of failure. However, they have been modernized over time and reliability has increased. Since about 2005 the CVT has become quite reliable and on the Audi A6 C6 it no longer has such pronounced problems as on the Audi A4 B6 and Audi A6 C5.
Before a purchase it is important to do a careful check. The operation must be perfect, there must be no evident slipping, extraneous sounds or rough gearbox operation.
ZF 6HP automatic gearbox
The 6-speed automatic transmission fitted here is the ZF 6HP in its 6HP19 and 6HP26 versions. It is a very interesting and widespread automatic gearbox, much more resistant than the CVT. The ZF 6HP19 version was used for engines up to 4.2 l and the 6HP26 version with the top V10 engines (5.0 l and 5.2 l). It was fitted to versions with Quattro all-wheel drive.
Thanks to the different structure and greater mechanical resistance, this type of gearbox is able to withstand more aggressive use. Even here however, aggressive use will decrease the overall life of the aggregate. The classic Tiptronic automatic transmission can reach 400,000 km (250 k miles) without major problems if it is used with care and if the oil is changed regularly. If, on the other hand, you drive too aggressively, already after 100,000 km (60 k miles) the hydraulic block could begin to give way and already at 200 – 250,000 km (125 – 155 k miles) there will almost certainly be large investments to be made.
Audi says you don’t need to change the oil in automatic gearboxes, but that’s not true. In any case, many residues are accumulated in the oil caused by normal wear and the more aggressive the use, the more often it must be replaced. In the ZF 6HP automatic transmission, the oil must be changed at least every 60,000 km (35-40 k miles).
After 150,000 km (95 k miles), rough gearbox operation may begin to be felt. Particularly prevalent on the Tiptronic gearbox are the small bumps between first and second gears which are more noticeable in slow-moving traffic. This behavior is normal and does not mean that the gearbox is dying.
More serious problems may appear after 200,000 km (125 k miles). The mechatronic, the torque converter and its lockup clutch may fail. The blocking system almost always works in partial attack mode. In addition to wearing the clutch, this also leads to rapid fouling of the oil with wear fragments. Dirty or degraded oil will lead to rapid wear of the solenoids and gearbox hydraulics which in turn will lead to rough running and accelerated wear of the entire unit.
Drivetrain and Transmission System
The Quattro all-wheel drive system is very effective, resistant and reliable. This is a permanent four-wheel drive system that transfers torque to all 4 wheels, but in different proportions. The Torsen differential is responsible for the correct functioning.
After 200,000 km (125 k miles) it may be necessary to replace the constant velocity joints and the intermediate bearing of the cardan shaft (drive shaft). Better to periodically check the quantity and quality of the oil in the rear differential. You shouldn’t notice any oil leaks because without lubrication it won’t last long.
Even front-wheel drive Audi A6 C6s perform quite well and do not give problems up to high mileage.
In general, the costs of original spare parts for the Audi A6 C6 drivetrain are quite high (as it is for a German premium car).
Suspensions, Steering and Brakes
The suspension has a fairly complex multilink structure, which is normal for this class of car. Suspension maintenance and repair costs can be high not only due to the low resistance of some elements, but also due to the extensive use of aluminum components.
After 120,000 km (75 k miles) the stabilizers and in some cases also the hub bearings will need to be replaced. Around 160,000 km (100 k miles) the shock absorbers need to be changed and around 200,000 km (125 k miles) all the silent blocks and some arms.
As already mentioned, the Audi A6 C6 could also be fitted with air suspensions which made it possible to vary the height of the car. With cars equipped with this suspension you have to be very careful. The air suspension itself is quite reliable, but sooner or later the time will come to repair it and here the price is really high.
Due to the high repair prices, some owners continue to use their Audi A6 C6 with broken air suspension. This way you risk ruining the compressor and the valve block as well.
Steering system
The steering is almost never a problem. In some rare cases the effort adjuster on the steering wheel may stop working. On cars with very wide tires, the life of steering tie rods and rod ends is relatively short. Problems with the steering rack and with the power steering pump usually appear only after 300 thousand km (185 k miles).
Brakes system
The brakes of the Audi A6 C6 are reliable and effective. However, the front discs and pads wear out relatively quickly. The discs last around 40 – 70,000 km (25 – 45 k miles) and the pads around 25 – 45,000 km (15 – 25 k miles). Obviously it depends a lot on the driving style, and if you drive calmly they can last longer. Replacing worn parts will cost a lot of money, especially if you use original parts or other high-quality parts.
Breakdowns of the parking brake are often encountered, but the reasons are usually purely electrical: the wiring that goes to the individual drive motors breaks, or the owners break the control button in the cabin.
Electronics and Electrical System
The Audi A6 C6s are equipped with a complex electrical system. Many electronic systems that over time could begin to give small problems. Since the system is very complex and there are many control units, any diagnostics and any work costs a lot and must only be carried out by specialized people.
Diagnostics by a good specialist is important as a certain problem can be caused by several reasons. For example if the battery stops recharging, it may be due to a broken alternator, due to problems with the voltage control system or for other reasons.
All Audi A6 C6s are equipped with the multimedia system MMI – Multi Media Interface. This has a screen in the central part of the center console and the control buttons are located between the two front seats near the gear selector. There are several versions of this system: 2G Basic, 2G High and after the restyling the 3G with navigator, DVD and hard disk. This system also allows you to view the mileage remaining before the next service, the oil level and even the battery charge level.
On cars of the first years of production, it happens that the MMI multimedia system freezes. In these cases it is usually sufficient to update the software. To carry out this procedure, if you do not have the appropriate knowledge, you will have to visit a specialized service centre. After 100,000 km (60 k miles), the CD player and radio station receiver may fail.
The climate control block can have various problems: failure of some gear motors, breakage of the fan motor, failure of the displays and other small malfunctions. Spare parts generally don’t cost much, but almost always the central console must be disassembled to carry out the repair work. This must be done very carefully, otherwise you risk breaking some fixings and the console will start to creak.
The LEDs in the headlights often burn out. The bad part is that to replace them you have to replace the entire headlight. The total cost will be great. The taillights can also stop working due to problems with the contacts. The headlight position correctors may stop working around 150,000 km (95 k miles).
After 100 – 150 thousand km (60 – 95 k miles), the parking sensors may also start to give problems. Both, the sensors themselves and their wiring are sensitive. There are failures of the steering lock module and failures of the electronic relays in the comfort block. The cooling system fan controller may fail due to oxidized contacts.
When there are steering lock defects, there can also be problems with starting the car due to its connection with the anti-theft system. If the ESP acceleration sensor stops working, there will be errors with the ABS and other related systems.
In the end we have to say that maintaining a car with such complex electronics will be expensive. This not only in the event of breakage, but also the most trivial procedures such as battery replacement require its entry in the control block.
Other
The car has a very good resistance to corrosion and some parts of the body are in aluminium. Only small traces of rust are acceptable, especially if the car has been used in places with a severe climate. If you find severe signs of rust, most likely the car was in an accident and then badly repaired.
The paint quality is also very good. If well maintained, even after many years the Audi A6 C6 does not lose its shine. Chrome elements are almost always in bad condition.
Over time, the headlights lose efficiency (the reflective element burns out). Some workshops are able to repair them, or new elements can be fitted at a higher price. If the headlight washers are rarely used, they could oxidize and not close completely. In LED taillights (installed after facelift) some LEDs can burn out. Here, too, you can try to find a good specialist who can repair them.
Power windows can wear out after about 200,000 km (125 k miles). After about 250 – 300 thousand km (155 – 185 k miles) the door locks can fail. A lock in bad condition or some damaged release button can lead to current leaks which quickly drain the battery.
The wiper mechanism is reliable, but it is made of aluminum, so it can oxidize if used infrequently. The antenna may also oxidize due to low water resistance.
The air conditioner compressor lives at least 250 thousand km (155 k miles), but only if you keep an eye on the amount of freon in the system.
Engines and their Problems
Diesel engines list :
| Version | Engine | Power | Top Speed | Acceleration | Fuel Consumption |
| 2.0 TDIe | 2.0 l EA189 (CAGB) | 136 hp | 208 km/h or 130 mph | 10.3 s | 5,3 l/100 km
US: 44,3 mpg UK: 53,3 mpg |
| 2.0 TDI | 2.0 l EA188 (BLB, BRE) | 140 hp | 210 km/h or 130 mph | 10.3 s | 6,2 l/100 km
US: 37,9 mpg UK: 45,5 mpg |
| 2.0 TDI | 2.0 l EA189 (CAHA) | 170 hp | 225 km/h or 140 mph | 8.9 s | 5,7 l/100 km
US: 41,2 mpg UK: 49,5 mpg |
| 2.7 TDI V6 | 2.7 l EA896 (BPP) | 180 hp | 230 km/h or 143 mph | 8.1 s | 6,8 l/100 km
US: 34,5 mpg UK: 41,5 mpg |
| 2.7 TDI V6 | 2.7 l EA896 (CANA, CANC) | 190 hp | 232 km/h or 144 mph | 7.9 s | 6,2 l/100 km
US: 37,9 mpg UK: 45,5 mpg |
| 2.7 TDI V6 quattro | 2.7 l EA896 (BPP) | 180 hp | 228 km/h or 141 mph | 8.9 s | 8,2 l/100 km
US: 28,6 mpg UK: 34,4 mpg |
| 2.7 TDI V6 quattro | 2.7 l EA896 (CANA, CANC) | 190 hp | 230 km/h or 143 mph | 8.2 s | 7,1 l/100 km
US: 33,1 mpg UK: 39,7 mpg |
| 3.0 TDI V6 quattro | 3.0 l EA896 (BMK) | 224 hp | 245 km/h or 152 mph | 7.3 s | 7,9 l/100 km
US: 29,7 mpg UK: 35,7 mpg |
| 3.0 TDI V6 quattro | 3.0 l EA896 (ASB) | 233 hp | 247 km/h or 153 mph | 6.9 s | 8 l/100 km
US: 29,4 mpg UK: 35,3 mpg |
| 3.0 TDI V6 quattro | 3.0 l EA896 (CDYA, CDYC) | 240 hp | 250 km/h or 155 mph | 6.6 s | 6,7 l/100 km
US: 35,1 mpg UK: 42,1 mpg |
Petrol/Gasoline engines list :
| Version | Engine | Power | Top Speed | Acceleration | Fuel Consumption |
| 2.0 TFSI | 2.0 l EA113 (BPJ) | 170 hp | 227 km/h or 141 mph | 8.4 s | 7,9 l/100 km
US: 29,7 mpg UK: 35,7 mpg |
| 2.4 V6 24v | 2.4 l EA837 (BDW) | 177 hp | 231 km/h or 143 mph | 8.9 s | 9,7 l/100 km
US: 24,2 mpg UK: 29,1 mpg |
| 2.4 V6 24v quattro | 2.4 l EA837 (BDW) | 177 hp | 230 km/h or 142 mph | 9.1 s | 10,9 l/100 km
US: 21,5 mpg UK: 25,9 mpg |
| 2.8 FSI V6 24v | 2.8 l EA837 (CCDA) | 190 hp | 238 km/h or 147 mph | 8.2 s | 8,2 l/100 km
US: 28,6 mpg UK: 34,4 mpg |
| 2.8 FSI V6 24v | 2.8 l EA837 (BDX) | 210 hp | 243 km/h or 150 mph | 7.9 s | 8,7 l/100 km
US: 27,1 mpg UK: 32,4 mpg |
| 2.8 FSI V6 24v | 2.8 l EA837 (CCEA) | 220 hp | 240 km/h or 149 mph | 7.3 s | 8,4 l/100 km
US: 28,0 mpg UK: 33,6 mpg |
| 2.8 FSI V6 24v quattro | 2.8 l EA837 (CCDA) | 190 hp | 237 km/h or 147 mph | 8.4 s | 8,7 l/100 km
US: 27,1 mpg UK: 32,4 mpg |
| 2.8 FSI V6 24v quattro | 2.8 l EA837 (BDX) | 210 hp | 237 km/h or 147 mph | 8.4 s | 9,7 l/100 km
US: 24,2 mpg UK: 29,1 mpg |
| 2.8 FSI V6 24v quattro | 2.8 l EA837 (CCEA) | 220 hp | 240 km/h or 149 mph | 7.3 s | 8,4 l/100 km
US: 28,0 mpg UK: 33,6 mpg |
| 3.0 TFSI quattro | 3.0 l EA837 (CAJA) | 290 hp | 250 km/h or 155 mph | 5.9 s | 9,4 l/100 km
US: 25,0 mpg UK: 30,0 mpg |
| 3.2 FSI 24v | 3.2 l EA837 (AUK) | 256 hp | 250 km/h or 155 mph | 6.9 s | 9,7 l/100 km
US: 24,2 mpg UK: 29,1 mpg |
| 3.2 FSI 24v quattro | 3.2 l EA837 (AUK) | 256 hp | 250 km/h or 155 mph | 6.8 s | 10,7 l/100 km
US: 21,9 mpg UK: 26,4 mpg |
| 4.2 V8 40v quattro | 4.2 l EA824 (BAT) | 335 hp | 250 km/h or 155 mph | 6.1 s | 11,6 l/100 km
US: 20,2 mpg UK: 24,3 mpg |
| 4.2 FSI V8 32v quattro | 4.2 l EA824 (BVJ) | 350 hp | 250 km/h or 155 mph | 5.9 s | 10,8 l/100 km
US: 21,7 mpg UK: 26,1 mpg |
| S6 | 5.2 l EA824 (BXA) | 435 hp | 250 km/h or 155 mph | 5.2 s | 13,4 l/100 km
US: 17,5 mpg UK: 21,1 mpg |
| RS6 | 5.0 V10 (BUH) | 580 hp | 250 km/h or 155 mph | 4.3 s | 13,9 l/100 km
US: 16,9 mpg UK: 20,3 mpg |
Diesel Engines
2.0 l TDI Engines
The 2.0 l TDI engine comes in two different generations in the Audi A6 C6: first generation 2.0 l TDI PD EA188 (unit injectors) and second generation 2.0 l TDI CR EA189 (Common Rail). The two generations differ greatly in terms of technical characteristics and reliability.
2.0 l TDI PD EA188 diesel Engine
The 2.0 TDI PD is a turbodiesel with unit injectors and it is the famous Volkswagen turbodiesel that can cause many problems. The most famous are the failure of the oil pump, cracks on the cylinder head, problematic unit injectors (at high mileage) and even the EGR valve that stops working.
The famous problems with cylinder head cracks are not present on all engine versions, but it is still advisable to pay attention to the cylinder head and its gasket.
The unit injectors turned out to be quite capricious, they do not like low-quality fuel and are expensive to repair if there is a problem. In good running condition, they shouldn’t cause major problems before 250,000 km (155 k miles).
There are frequent cases in which the engine begins to consume oil, even up to 0.5 – 1 l per 1000 km (620 miles).
The drive mechanism of the oil pump has proved to be problematic and may be in bad shape already at around 200,000 km or 125 k miles (in some cases even earlier). This is why you need to keep an eye on it and check it periodically (perhaps when replacing the timing belt). It is difficult to tell if a pump is in bad shape without disassembling. In fact, the pressure remains unchanged and there are no strange noises until complete failure.
The coolant pump can start whistling even before 100,000 km (60 k miles). A new pump could cost a lot.
At high mileages, there are problems with the turbine, with the flywheel and also with the EGR valve. These are now typical for modern turbodiesels. Power losses are sometimes caused by blockage of the turbine management system.
Despite everything, these engines, if treated well, can go without fatal defects up to 275 – 300 thousand km or 170 – 185 k miles (and even more).
2.0 l TDI CR EA189 diesel Engine
The 2.0 l TDI CR is the Common Rail version which is much more reliable and has solved almost all the problems that were previously on the unit injector version. This is especially true for engines manufactured after 2009 (the initial production ones had some major weaknesses, however).
The 2.0 l TDI Common Rail is present here in two power versions. In addition to the 170 HP version, there is also the 2.0 TDIe version with reduced power. The small “e” indicates that the engine has been adapted to pollute less. The Audi A6 C6 2.0 TDIe have decreased power, the particulate filter and more efficient tires.
The versions of the first production period (until 2009) have maintained the problem of the oil pump and its drive system. However, this only applies to versions equipped with balancing shafts. In addition, the piezoelectric injectors of the Common Rail system proved to be capricious. In general, the 2.0 TDI EA189 Common Rail diesel engine is sensitive to the quality of the diesel. At mileages close to 100,000 km (60 k miles) you may have difficulty starting the engine when it is hot. The fault generally lies with the delivery valve or the pressure reduction valve.
The Bosch CP4 high-pressure injection pump could be damaged due to the worn fuel pump in the tank. If the car has suddenly turned off while you are on the road or if the car simply does not start, in no case should you force it trying to start it several times. The diesel-free high-pressure injection pump will run dry and therefore wear out. Metal shavings caused by dry running can foul the entire injection system and damage the injectors. The injectors are not repairable (in most cases). The final repair cost will be very high.
In addition, the initial versions of the engine were equipped with an intake manifold with swirl flaps. The drive mechanism of these has not proved too reliable.
Since 2009, these engines have been modernized. The injectors became electromagnetic, the swirl flaps were eliminated, the oil pump problem was solved and other improvements were made.
On all engine versions, leaks may appear from under the valve cover. Often the owners consider this problem insignificant, but then regret it when the oil spoils the timing belt and it breaks.
For the rest, there may be the typical problems of modern diesels: the EGR valve that gets dirty and stops working and the DPF filter that clogs and causes malfunctions (especially on cars used mainly in the city). A 2.0 l TDI EA189 diesel engine treated well, however, manages to live more than 350,000 km (220 k miles) without fatal failures.
2.7 l and 3.0 l TDI V6 EA896 diesel Engines
The 2.7 l and 3.0 l TDI V6 engines fitted here are those of the EA896 series. They are very similar technically, but they also have some differences.
As already mentioned, the V6 diesel engines are of the EA896 series. However, this series can be divided into two generations: the first generation produced until 2007 (generally with a 3-letter engine code, for example BPP) and the second generation “EVO” which appeared at the end of 2007 (generally with a 4-letter engine code , for example CANA).
The 3.0 l TDI in the initial production period was relatively problematic, it had some so-called “childhood flaws”, but over the years it was always perfected until it became a very robust and reliable unit. Neither the first generation nor the second generation engines can be defined as totally ideal.
Among the most widespread problems we have those with the timing mechanism. The problem lies not in the low service life (in fact, it generally lasts at least 200 – 300 thousand km or 125 – 185 k miles), but in the location of the mechanism. Here the latter is no longer in front as usual, but on the side of the gearbox and to carry out the difficult replacement work you have to pay a lot of money. In some unfortunate cases the chain tensioner already fails after 150 – 200,000 km (95 – 125 k miles) and even in this situation expensive repairs have to be carried out.
Even though the replacement prices are great, don’t ignore the noises coming from the chain. If the problem is not solved in time, the chain could slip and risk damaging the valves. If this happens, the final cost of the repair will be very large.
Another weak point is the injection system with piezoelectric injectors. Over time, these can begin to leak and in the worst case cause damage to the engine (e.g. burn valves and pistons). Piezo injectors cost a lot and are difficult to repair. The drive belt of the high pressure pump can break as early as 100 thousand km (60 k miles). The pump itself is also problematic on some engine versions.
Over time the heat exchanger may begin to leak. Problems with the intake manifold where the swirl flaps get stuck are common. At high mileage the typical problems with particle filter and EGR valve will be unavoidable.
The 3.0 l TDI is a fairly reliable engine, which gives a lot of thrills but is relatively expensive to maintain at high mileage.
The 2.7 TDI is the smaller brother of the 3.0 TDI, so it is also technically similar. It also has the same weaknesses and about the same characteristics.
Petrol/Gasoline Engines
2.0 l TFSI EA113 Engine
The 2.0 l TFSI of the EA113 series is the only petrol engine with 4 cylinders. It is relatively weak for the big Audi A6 C6 and will be suitable for quiet driving. However, it must be said that these engines are very suitable for tuning and much greater powers can be obtained with a simple chip tuning (modification of the control unit software).
It is a relatively complex engine for the period, the manufacturer has decided to combine direct injection and the turbine. From a mechanical point of view it is a fairly robust unit, but there are some important weak points. It suffers from excessive oil consumption and accumulations of dirt (soot) in the engine head. To eliminate oil consumption, the original pistons must be replaced with reinforced ones.
The timing system (combining a belt and a chain) must be replaced every 90 thousand km (55 k miles). Already at 100 thousand km (60 k miles), the phase regulator or the pusher of the high pressure pump can break. The ignition coils and N249 bypass valve also have a modest life span.
There may also be accumulations of dirt in the intake (typical for engines with direct injection). Problems with the thermostat and intake manifold can also be mentioned. The latter is by no means cheap.
The turbine is reliable and lives between 150,000 km (95 k miles) and 300,000 km (185 k miles) depending on usage. With proper use, it lives for many kilometers.
We have already mentioned the good potential in tuning, in fact engines of the same series have been mounted on Golf GTI, GOLF R, Audi S3, Audi TTS on which it reaches powers even higher than 300 hp.
EA837 V6 Engines
The EA837 V6 engine series appeared in 2004 and was installed in almost all models of the company. These engines are divided into four generations, which differ in the type of injection and the presence of a turbocharger. Only the first three generations can be encountered here.
The first generation includes the 2.4 l (multipoint injection) and 3.2 l FSI engines (direct injection and 3123 cm³ volume). These received a silumin cylinder block and a very complex timing system: four chains, two intermediate gears and a balancer shaft. All camshafts had phase adjusters.
In 2006, the second generation arrived, comprising the 2.8 l FSI (direct injection) and 3.2 l FSI (direct injection and 3197 cm³ volume) engines. The difference of the new engines was the alusil block and the AVS valve control system. The timing chain tensioners have been modified to increase reliability.
In 2008, the third generation debuted on the restyling version of the Audi A6 C6. This only includes the new 3.0 l TFSI. These engines have direct fuel injection and supercharging via an Eaton compressor. The aluminum block, cylinder heads and timing chain have been redesigned to handle more horsepower.
2.4 l EA837 Engine
The 2.4 l MPI EA837 is the only engine in the series that has multipoint injection. It has a relatively simple structure and is one of the longest-lasting petrol engines mounted on the Audi A6 C6.
The typical problems of this engine are: breakage of the thermostat and of the swirl flaps in the intake manifold.
Scratches on the cylinder walls are not uncommon. This can lead to power loss, exhaust smoke and increased oil consumption. After 100,000 km (60 k miles), oil consumption can also increase due to wear on the piston rings and valve stem seals.
Another famous problem is the stretching of the timing chains and the breakage of their tensioners. Phase regulators and ignition coils are not among the most reliable elements.
To minimize the amount of possible problems, it is advisable to change the oil often, use good quality gasoline and not overheat the engine. Otherwise, a well-treated engine should have no fatal defects for at least 280,000 to 300,000 km (175 – 185 k miles).
2.8 l FSI EA837 Engine
The 2.8 l FSI EA837 is part of the second generation of the series. Despite the improvements made in the design phase, the problems have not completely disappeared.
Here, too, there may be scratches on the cylinder walls. These are almost always caused by the faulty injectors leaking. The timing mechanism has become a little more reliable, but still it cannot be called immortal, and the replacement cost is also not low.
Phase variators and ignition coils have a relatively short life. There are cases of excessive oil consumption and dirty intake valves.
3.2 l FSI EA837 Engine
The 3.2 l FSI engine mounted here is the first generation one with 3123 cm³. It is very similar to its smaller 2.4 l brother, but has direct injection and a larger volume. The weaknesses are about the same.
Here, too, problems with the timing chains are often encountered. After about 150,000 km (95 k miles) these begin to stretch and the hydraulic chain tensioner breaks. To replace the timing mechanism, the engine must be removed due to its awkward position and the final cost can be large. After carrying out the procedure, you can rest assured for the next 100 – 150,000 km (60 – 95 k miles). The first signs of wear are strange noises and strong vibrations in the first seconds after starting a cold engine. Better to intervene as soon as possible to avoid bigger problems.
There is also oil consumption caused by scratches on the cylinder walls or worn piston rings. The complex intake system does not prove to be very reliable. The intake valves can become dirty due to direct injection.
To avoid problems on this engine you need to change the oil often and use it very gently when it is not yet hot. It will also be good to use good gasoline and keep the operating temperatures low. A well treated engine will last for at least 260,000 km (160 k miles).
3.0 l TFSI EA837 Engine
As already mentioned, the 3.0 TFSI engine does not have a turbine, but an Eaton compressor. The 3.0 l TFSI EA837 belongs to the third generation of the series, but here too there are some major weaknesses.
The main weak point is precisely the lining of the cylinder walls which fails to hold up over time and very often scratches are encountered on the cylinder walls. This leads to large oil consumptions (even more than 1 liter of oil every 1000 km or 620 miles). The main culprits for the destruction of the coating are low-quality gasoline and the stress on a cold engine. There are cases where at high mileage the catalytic converters are destroyed, so some particles can end up in the engine and ruin the cylinder walls.
Oil consumption could also be caused by problems with the pistons. Often the defect already appeared in the warranty period and there have been recalls intended to solve the problem. Often under warranty they also changed the thermostat, in cases of serious damage to the engine, the cylinder block could also be changed.
Another serious problem is the lengthening of the timing chains. For some reason, on this generation of engines the engineers decided not to install check valves in the cylinder head and all the oil flows into the sump, so the camshafts run “dry” on start up and the chain stretches very quickly. It can happen even at 80 – 120 thousand km (50 – 75 k miles). Their duration also depends on the driving style.
The problems mentioned so far are very expensive to fix.
Due to direct injection, the valves become covered with dirt over time, which can lead to unstable engine operation and even burning of the valves. The solution is simple – every 30-45 thousand km (20 – 30 k miles) it is necessary to clean the valves.
The coolant pump and the high pressure pump in the injection system do not have a very long service life.
4.2 l V8 EA824 Engine
The V8 engines in the Audi A6 C6 have a beautiful sound and good performance. It is the 4.2 l engine, but in two different generations.
The first generation 4.2 l has multipoint fuel injection, an aluminum block, a long timing belt and a pair of short chains between the camshafts fitted with hydraulic chain tensioners which acted as a phase adjuster.
The 4.2 l FSI is part of the second generation (arrived in 2006) and has direct injection, a timing chain and phase adjustment system on all camshafts. Also, on the basis of this unit, the largest 5.2-liter 10-cylinder FSI engine was created.
The first generation 4.2 L V8 looks pretty good. It is a robust and reliable engine. Despite the aluminum block, scratches on the cylinder walls are rarely encountered. They generally appear due to the low frequency of the services or due to overheating.
Most of the problems here are caused by the unreliable hydraulic chain tensioners. Even with the belt you have to be careful, if it breaks the valves will be damaged. Oil leaks are common, especially at the point of contact between the engine and gearbox.
The newer 4.2 l FSI performs worse in terms of reliability. Large oil consumption caused by scratches on the cylinder walls are much more frequent. After about 200,000 km (125 k miles), the timing chains stretch, and their replacement is complex and expensive.
The direct injection system is not exactly ideal and can very often cause serious problems. For example, this causes dirt deposits to accumulate on the intake valves.
The plastic intake manifold can leak over time. The oil separator and the ignition coils can also be listed among the weak points of the unit.
Engines treated well can exceed 260 – 300 thousand km (160 – 185 k miles) without fatal breakdowns.
Conclusions and Advice & Tips for buying used
The Audi A6 C6 is a premium car that has a lot going for it, but it can also demand a lot. A car in bad condition, bought at a very low price on the used market, will most likely give a lot of problems and leave a bad impression. A good car, on the other hand, will only require ordinary maintenance and will give you a lot of satisfaction.
We have mentioned many possible problems concerning the Audi A6 C6, however we must specify that many of these are generally caused by carelessness and incorrect maintenance. Despite all the things said, the Audi A6 C6 is quite a reliable car and something serious doesn’t necessarily have to happen.
Before a possible purchase, a detailed check must be made, paying close attention to every single detail. Thanks to the high-quality interior, there may not be too large signs of wear even at 300,000 km (185 k miles). On such cars scammers easily lower the mileage.
The main competitors of the Audi A6 C6 are: BMW 5 Series E60, Mercedes-Benz E Class W211, Mercedes-Benz CLS, Volvo S80, Peugeot 607, Lexus GS and other similar cars.
The most important thing is to find a car in good general condition.