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Home » Audi A6 [C5](1997-2004) Problems, Review, Faults and Information

Audi A6 [C5](1997-2004) Problems, Review, Faults and Information

Audi A6 C5 came on the market in 1997 when it replaced the previous Audi A6 C4. This is the second generation of this model. In 2001 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 2004 when it was replaced by the new generation Audi A6 C6. Let’s see the Audi A6 C5 review with the most important information, faults and common problems.

Table of Contents

Review of the Audi A6 C5 with all the information, defects, issues, faults, weaknesses, problems and maintenance costs.

Impressions, Interior and Comfort

Audi A6 C5 is a high-end car which in 2000 – 2001 was considered one of the top 10 cars of the moment and made strong competition to BMW 5 Series E39 and Mercedes-Benz E-Class W210. This did not happen by accident, in fact the Audi A6 C5 has improved a lot compared to the previous generation in several aspects.

The great improvements in terms of comfort, road control and performance are accompanied by a complex electronic system, complex and expensive suspensions, complex engines and gearboxes. Later we will see how such a complex car behaves from the point of view of reliability and we will see if the maintenance costs will not be exaggerated.

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. Quattro is a very good permanent all-wheel drive system with a Torsen differential.

The front suspensions are quite refined, with a high wishbone with a virtual steering axis with split joints in correspondence with both the lower and upper triangles with cast iron hub carriers and aluminum links. The rear suspensions can be different: on cars with front-wheel drive there is a torsion beam with Panhard bar (Panhard rod), on cars with all-wheel drive there is a low wishbone system with overlapping triangles. In addition to the general complexity of the suspensions, extensive use of aluminum alloys is made to contain weight. As we will see later, all this can lead to large maintenance costs.

The body design is now old, but can still please. The style is calm, soft and aerodynamic. On the Audi A6 C5 there is a Cx of just 0.28 (one of the lowest on sedans of the period). At the time of production it was considered one of the most beautiful cars on the market. As already mentioned, in May 2001 the Audi A6 C5 underwent restyling. The differences between restyling and pre-facelift cars are: increased headlights, enlarged right mirror, new taillights and chromed grille frame on the front bumper (previously this frame was seen only on Audi A6 C5 with V8 engines).

Review of the Audi A6 C5 Avant station wagon with all the information, defects, issues, faults, weaknesses, problems and maintenance costs.

Audi A6 C5 Avant (station wagon)

Aesthetically, the car is attractive, both before and after the restyling, especially in the more equipped versions.

The second generation Audi A6 is available in two body styles: sedan (4-door) and Avant (station wagon). The German car has a length of 4796 mm, a width of 1819 mm and a height of 1477 mm. The wheelbase is 2760 mm. The weight of the car varies from 1320 to 1765 kg depending on the version.

At the end of 1999, the sports version Audi S6 appeared. In 2003, the even more powerful version Audi RS6 and the associated station wagon Audi RS6 Avant appeared.

There is also an off-road version called the Audi Allroad (which is considered a separate model).

Comfort and Practicality

Seeing as this is an Audi A6, you’d expect a large amount of interior space, but the reality is different. This is an older A6 that isn’t nearly as big as a modern generation. Just think that the dimensions of the Audi A6 C5 are comparable to those of the Audi A4 B8 and the wheelbase is even slightly shorter, so the amount of interior space is also similar.

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 trunk/boot has a volume of 551 liters in the sedan and 455 liters in the station wagon (by completely folding down the rear sofa, the volume can reach 1590 litres).

Ride comfort is very good. In the end, this is a premium German sedan, so the Audi A6 C5 is very comfortable and at the same time stable and easily controllable. You can find Audi A6 C5 with air suspension which improves the situation even more.

All together it makes the Audi A6 C5 a pleasant car both in and out of the city. Even on longer journeys you shouldn’t get so tired.

Interior and Equipment

in this photo you can see the interior compartment of the Audi A6 C5 with the steering wheel, the stereo radio, the seats and the dashboard central panel cockpit

High-quality materials have been used inside, and the build quality is also good. One of the few elements that cause noise inside is the rear sofa which creaks from time to time. Comfort and ergonomics are at a high level, as is the case with a premium German car.

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. The problem with the buttons becomes very apparent as they are made of white plastic, so even the slightest deterioration of the fragile paint is visible. 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.

The soundproofing is very good and the interior remains silent in any situation.

Given the large amount of electronics inserted in the Audi A6 C5, the possibility has appeared of offering many systems intended to increase comfort and safety. Obviously there are also quite “poor” specimens that have only what is strictly necessary, but there are also very “rich” specimens that can offer everything. You can have automatic climate control, comfortable leather seats with heating, a multifunctional steering wheel, an automatic gearbox and much more.

The basic multimedia system is good, but offers few features and has acceptable audio quality. Optionally, you can have a more sophisticated system, with a display and more features. The Bose sound system will also offer very good sound quality.


The body of the Audi A6 C5 was built according to the latest safety technologies of the time. Thanks to this, the German sedan performed well in crash tests. The car feels massive and well assembled.

In the EuroNCAP safety test, the Audi A6 C5 got 4 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.

It did not get the maximum score due to knee injuries that the driver could suffer in a head-on collision.

Reliability and Issues

Gearbox and Transmission

The Audi A6 C5 could be fitted with a manual gearbox (5 or 6-speed) or the 5-speed automatic gearbox with DSP dynamic program (the program adapts to the driver’s driving style and also takes into account the state of the road). The Tiptronic system of the automatic gearbox allowed switching to manual mode if necessary. Since 2000 it has become possible to mount the Multitronic variator. With the 1.9 TDI engine, the 4-speed automatic transmission could be fitted.

Manual transmission

The manual gearbox is the most reliable. Up to 200,000 km (125 k miles) it shouldn’t give any problems. Beyond this mileage there may be difficulties in shifting gears. Sooner or later the dual-mass flywheel will have to be replaced, which has a high price. Clutch and flywheel have a fairly good life, but it all depends on how you use the car.

ZF 5HP automatic gearbox

The 5-speed automatic transmission initially fitted was the ZF 5HP19FLA (01V) which after 1998 was replaced by the reinforced version 5HP24A (01L).

The ZF 5HP automatic gearbox as well as being quite fast for its period, is also very reliable in general. Obviously it has some weaknesses, this is especially true for the versions from the early production period. Although it can be capricious, in general the Tiptronic is quite long-lived. Its declared service life is 300,000 km (185 k miles), but the first problems can appear after 180 – 200,000 km (110 – 125 k miles).

The main problems are the failure of the oil pump and the premature wear of the torque converter and its lock-up clutch. Generally after 200,000 km (125 k miles) you may start to feel knocking during downshifts. These are often caused by worn solenoids and various sensors.

The valves in the hydraulic block (Valve Body) can wear out over time and this will cause rough gearbox operation. There can be also problems with the drums.

In general, it must be said that everything depends a lot on the driving style and maintenance. If you drive calmly and change the oil at least every 50 – 70,000 km (30 – 45 k miles), the gearbox can achieve the 300,000 km (185 k miles) declared by the manufacturer without fatal defects. Some carefully treated gearboxes can even reach 400 – 500,000 km (250 – 300 k miles).

Multitronic CVT (continuously variable transmission)

The Multitronic variator (continuously variable transmission )has been available since 2000 and is the most problematic of all gearboxes. This is the 01J model (also known as Multitronic VL-300). It has been designed to withstand engines up to 3.0 l and with a maximum torque of 310 Nm.

It was proposed as a simple and long-lived automatic transmission, with great potential, but in the end all this did not prove to be true. Reliability didn’t prove to be very great, especially in the early years of production. However, it must be said that the manufacturer has always tried to improve it and the more recent versions perform better.

Its weakest point is the electronic control block. Due to malfunctions of the latter, accelerated wear may appear. The variator is very afraid of overheating, these generally “kill” the electronic control block. The used chain needs to be replaced approximately every 100,000 km (60 – 65 k miles). It is often necessary to change the pump and all three solenoids of the electric regulator as well.

However, it must also be said that on some cars the variator lives for a long time without problems. It seems to depend a lot on driving style, year of manufacture and maintenance. As already mentioned, the variators mounted on the Audi A6 C5 have undergone several modernizations aimed at solving the initial problems and the specimens of the last years of production are quite reliable. Only the life of the chain has not increased. It is advisable to avoid aggressive accelerations and change the oil every 50,000 km (30 k miles). The variators of recent years, if used with care, can even reach 250 – 300,000 km (155 – 185 k miles).

Drivetrain and Transmission System

Front-wheel drive Audi A6 C5s will have no problems up to high mileage. Periodically it is advisable to check the protections of the constant velocity joints. If these are worn and dirt enters them, the constant velocity joints will be damaged. With a little attention there will be no problems for at least 200,000 km (125 k miles).

Quattro all-wheel drive system is not a problem. For a long life it is good to keep under control the oil level and its quality in the various essential aggregates. Over time there will be wear on the silentblocks and oil seals. The reduction gearbox may begin to rumble after 300 – 400 thousand km or 185 – 250 k miles (generally due to bearing wear). At such high mileages, even the cardan shafts (drive shafts) fail.

Suspensions, Steering and Brakes

Suspensions are complex and fragile. They are more fragile than those of BMW and Mercedes competitors.

The suspension of the Audi A6 C5 lives at least 100 – 120,000 km (60 – 75 k miles) until the first problems. Obviously the duration varies according to the driving style and the state of the roads. Among the first elements to fail are obviously the stabilizers, but here the repair costs are not high.

The most expensive in maintenance will be the aluminum multilink front suspension. For a complete repair of the front suspension, using original spare parts, a lot of money will have to be spent. If you try to save by changing only the silent blocks or using non-original spare parts, the costs will be 2 – 3 times lower.

The lower arms of the rear suspension are also not very durable and for these you can find separate silentblocks only from alternative manufacturers. The outer lower silentblocks of the hubs are also relatively fragile at the rear. Poor rear suspension condition will be indicated by uneven tire wear.

Even worse is the situation if air suspension is fitted. These are reliable, but when it comes time to repair them, the costs will be very high.

The hub bearings reach 200,000 km (125 k miles) without major problems.

Steering system

The hydraulic power steering pump goes up to 200 – 300,000 km (125 – 185 k miles). Beyond this mileage, not only the pump but also the steering rack will need to be repaired.

Brakes system

On Audi A6 C5s manufactured before 1999, care must be taken with the brakes. Due to poor impermeability, the efficiency of the braking system could be lost. Moisture can get into the vacuum pump and ruin it.

If the brakes are in good condition, they work well and are efficient. Durability of the discs and pads is quite good.

Electronics and Electrical System

The large amount of electronics combined with their great age can lead to several problems. In some cases they are serious, in others they are just plain annoying.

The electrically adjustable seats could move by themselves from time to time and the heating could also switch on by itself. The doors can lock themselves leaving the owner outside.

The ABS and airbag control units can stop working. This usually happens due to oxidation of some contacts. The wrong position of the comfort control unit can lead to malfunctions of the latter. If this happens there will be problems mainly with the control of the electric windows and the interior lighting. These control units are positioned under the driver’s feet and risk being invaded by water.

Among the most innocent, but still annoying problems we can also mention the malfunctioning of the various indicators on the dashboard (temperature indicator, fuel level indicator and others). Often the only solution is to completely change the instrument cluster. Dashboards built between 2000 and 2001 are particularly sensitive. The on-board computer and air conditioning displays could also break.

The direction lights and hazard warning lights control relay can be fragile and problematic.

The electrical coolant temperature sensor could cause relatively many problems. This could give wrong indications (indicating too high a temperature). Because of this you may have difficulty starting the engine. The life of the sensor is quite unpredictable. It may break within a radius of 20 – 150,000 km (10 – 95 k miles). The price of a new sensor is not very high.

After 200,000 km (125 k miles) the oil temperature sensor will need to be changed. This before dying could begin to leak oil. At these mileages, the fuel level sensor and water pump will be near the end.

After 250,000 km (155 k miles) there could be problems with starting the hot engine. The cause of the difficulties is often electronic in nature. The culprits can be: relay, crankshaft position sensor or fuel pump.

Due to the complicated electronics, current leaks may appear on some cars. These power leaks can drain the battery even after 2 – 3 days (in the worst cases even overnight).


The body has good corrosion resistance and the paint is also of a fairly high quality. Small traces of rust can be seen on Audi A6 C5s from the first years of production, especially on cars that live in places with a particularly severe climate. The well maintained and accident free Audi A6 C5s are still aesthetically pleasing. On the other hand, if the car has been in an accident and then poorly repaired, you can encounter large signs of rust.

Despite the initial good quality of the paint, after so many years it is difficult to find an car with the paintwork still in good condition. Scratches and a loss of initial shine can be seen on almost all cars. Chrome elements are almost always in bad condition.

After 200,000 km (125 k miles) there could be problems with the catalytic converter. The latter loses its efficiency and increases consumption, decreases performance and causes irregular operation of the engine at idle.

The wiper mechanism is not immortal and on older cars it gives way. The headlights lose efficiency over time (the reflecting element burns out). Some workshops are able to repair them, or new elements can be fitted at a higher price. After 300 – 400 thousand km (185 – 250 k miles) the alternator will need to be repaired or replaced.

Engines and their Problems

Diesel engines list :

Version Engine Power Top Speed Acceleration Fuel Consumption
1.9 TDI 1.9 l EA180 (AFN, AVG) 110 hp 194 km/h or 120 mph 12.3 s 5,2 l/100 km

US: 45,2 mpg

UK: 54,3 mpg

1.9 TDI 1.9 l EA188 (AJM) 115 hp 196 km/h or 121 mph 11.6 s 5,6 l/100 km

US: 42 mpg

UK: 50,4 mpg

1.9 TDI 1.9 l EA188 (AWX) 130 hp 203 km/h or 126 mph 10.5 s 5,7 l/100 km

US: 41,2 mpg

UK: 49,5 mpg

2.5 TDI 2.5 l EA330 (AFB, AKN) 150 hp 218 km/h or 135 mph 9.7 s 6,2 l/100 km

US: 37,9 mpg

UK: 45,6 mpg

2.5 TDI quattro 2.5 l EA330 (AFB, AKN) 150 hp 216 km/h or 134 mph 9.9 s 6,9 l/100 km

US: 34,1 mpg

UK: 40,9 mpg

2.5 TDI 2.5 l EA330 (AYM) 155 hp 219 km/h or 136 mph 9.7 s 6,9 l/100 km

US: 34,1 mpg

UK: 40,9 mpg

2.5 TDI 2.5 l EA330 (BFC, BCZ, BDG) 163 hp 222 km/h or 138 mph 9.3 s 6,9 l/100 km

US: 34,1 mpg

UK: 40,9 mpg

2.5 TDI quattro 2.5 l EA330 (BFC, BCZ, BDG) 163 hp 203 km/h or 126 mph 10.4 s 8,7 l/100 km

US: 27 mpg

UK: 32,5 mpg

2.5 TDI 2.5 l EA330 (AKE, BDH, BAU) 180 hp 221 km/h or 137 mph 8.9 s 8,1 l/100 km

US: 29 mpg

UK: 34,8 mpg

2.5 TDI quattro 2.5 l EA330 (AKE, BDH, BAU) 180 hp 223 km/h or 138 mph 8.9 s 8,1 l/100 km

US: 29 mpg

UK: 34,8 mpg

Petrol/Gasoline engines list :

Version Engine Power Top Speed Acceleration Fuel Consumption
1.8 20v 1.8 l EA827 (AJP, AQE, ARH) 125 hp 203 km/h or 126 mph 11.3 s 7,9 l/100 km

US: 29,7 mpg

UK: 35,7 mpg

1.8 20v turbo 1.8 l EA827 (AEB, APU, ANB, AWT, ARK) 150 hp 217 km/h or 135 mph 9.4 s 7,9 l/100 km

US: 29,7 mpg

UK: 35,7 mpg

1.8 20v turbo quattro 1.8 l EA827 (AEB, APU, ANB, AWT, ARK) 150 hp 216 km/h or 134 mph 9.5 s 8,8 l/100 km

US: 26,7 mpg

UK: 32,1 mpg

1.8 20v turbo 1.8 l EA827 (AJL) 180 hp 230 km/h or 143 mph 8.5 s 8,2 l/100 km

US: 28,7 mpg

UK: 34,4 mpg

1.8 20v turbo quattro 1.8 l EA827 (AJL) 180 hp 227 km/h or 141 mph 8.5 s 9,2 l/100 km

US: 25,5 mpg

UK: 30,7 mpg

2.0 20v 2.0 l EA113 (ALT) 130 hp 205 km/h or 127 mph 10.5 s 8,3 l/100 km

US: 28,3 mpg

UK: 34 mpg

2.4 V6 30v 2.4 l EA835 (ALW, ARN, ASM) 136 hp 210 km/h or 130 mph 10.4 s 8,8 l/100 km

US: 26,7 mpg

UK: 32,1 mpg

2.4 V6 30v 2.4 l EA835 (AGA, APS, AML, ALF, ARJ) 165 hp 222 km/h or 138 mph 9.1 s 8,8 l/100 km

US: 26,7 mpg

UK: 32,1 mpg

2.4 V6 30v quattro 2.4 l EA835 (AGA, APS, AML, ALF, ARJ) 165 hp 220 km/h or 137 mph 10.8 s 10,8 l/100 km

US: 21,7 mpg

UK: 26,1 mpg

2.7 V6 30v turbo 2.7 l EA835 (AJK, AZA) 230 hp 245 km/h or 152 mph 7.3 s 10,6 l/100 km

US: 22,2 mpg

UK: 26,6 mpg

2.7 V6 30v turbo quattro 2.7 l EA835 (AJK, AZA) 230 hp 245 km/h or 152 mph 7.1 s 11,6 l/100 km

US: 20,2 mpg

UK: 24,3 mpg

2.7 V6 30v biturbo quattro 2.7 l EA835 (ARE) 250 hp 248 km/h or 154 mph 6.8 s 11,6 l/100 km

US: 20,2 mpg

UK: 24,3 mpg

2.8 V6 30v 2.8 l EA835 (ACK, APR, AMX, AQD, ALG) 193 hp 236 km/h or 147 mph 8.2 s 9,9 l/100 km

US: 23,7 mpg

UK: 28,5 mpg

2.8 V6 30v quattro 2.8 l EA835 (ACK, APR, AMX, AQD, ALG) 193 hp 234 km/h or 145 mph 8.0 s 10,8 l/100 km

US: 21,7 mpg

UK: 26,1 mpg

3.0 V6 30v 3.0 l EA835 (ASN) 220 hp 243 km/h or 151 mph 7.5 s 9,7 l/100 km

US: 24,2 mpg

UK: 29,1 mpg

3.0 V6 30v quattro 3.0 l EA835 (ASN) 220 hp 240 km/h or 149 mph 7.6 s 11,3 l/100 km

US: 20,8 mpg

UK: 25 mpg

4.2 V8 40v quattro 4.2 l EA824 (ARS, ASG, BAS) 300 hp 250 km/h or 155 mph 6.9 s 13 l/100 km

US: 18,1 mpg

UK: 21,7 mpg

S6 4.2 l EA824 (AQJ, ANK) 340 hp 250 km/h or 155 mph 5.7 s 14,1 l/100 km

US: 16,7 mpg

UK: 20 mpg

RS6 4.2 l bi-turbo EA824 (BCY) 450 hp 250 km/h or 155 mph 4.7 s 14,6 l/100 km

US: 16,1 mpg

UK: 19,3 mpg

RS6 Plus 4.2 l bi-turbo EA824 (BRV) 480 hp 280 km/h or 174 mph 4.6 s 14,5 l/100 km

US: 16,2 mpg

UK: 19,5 mpg

problems and issues with petrol, gasoline, LPG, CNG, methane and diesel engines mounted on Audi A6 C5

The engines in the Audi A6 C5 are generally considered to be quite reliable, but of course they are not without their flaws. The problems that appear are usually caused by high mileage, great age and poor maintenance.

Diesel Engines

Diesel engines have proven to be reliable and long-lasting, but they also need attention and quality fuel. First of all we want to make some clarifications to better understand which aggregates exactly have been mounted.

For example, the 1.9 l TDI engines are not all the same, initially the old units of the EA180 series were mounted, then the newer ones of the EA188 series arrived. The 2.5 l TDI engines are the V6 version (6 cylinders) of the EA330 series and not the R5 engines (5 cylinders in line).

1.9 l TDI EA180 diesel Engines

The smallest and weakest diesel engine is the 1.9 l TDI. Initially the EA180 series was mounted which here offers a power of 110 hp.

The engines of the EA180 series are equipped with direct injection with a Bosch VP37 high-pressure pump. Furthermore, the engines are equipped with a flowmeter and in the more powerful versions you can find a variable geometry turbine. For the rest, they have a fairly classic structure with a cast iron block, an aluminum head with 8 valves and an intermediate shaft which drives the oil pump and the vacuum pump.

The 1.9 l TDI EA180 engine is very reliable and problems start to appear at high mileages. You can burn the valve seats and this leads to a loss of compression. A loss of power can be caused by a blocked turbine geometry control system or a dirty EGR valve.

Often the lower flange of the crankcase ventilation pipe cracks and oil leaks appear. It is important to keep the service belt under control which, in the event of breakage, can end up under the timing belt leading to bad consequences.

In general, these engines manage to live even more than 400 – 500 thousand km (250 – 310 k miles) without fatal failure.

1.9 l TDI PD EA188 diesel Engines

Later, the 1.9 l TDI in its latest generation EA188 was also installed in the Audi A6 C5.

This has undergone some major changes. The injection system has become PD “Pumpe Düse” Unit Injectors, the intermediate shaft has been removed and a chain has been added to drive the oil pump.

From the point of view of reliability and longevity, the latest generation of the legendary 1.9 l TDI has deteriorated slightly compared to the past, but still performs very well. This is due to the fact that it has become more modern and complex. You must use only high quality oil and not have too long service intervals. Bad oil contributes to wear of the hydraulic compensators (hydraulic pushers) and camshaft cams.

A loss of power or erratic operation can be caused by a blocked turbine geometry control system. When the odometer passes over 200,000 km (125 k miles) there may be problems with the turbine itself, the dual-mass flywheel and fuel injectors. The single bolt fixing system of the unit injectors is not too reliable and over time could give way causing leaks.

In general, the duration of these aggregates depends a lot on the style of use. The cars used mostly on the highway and at constant speed can reach 300 – 400,000 km (185 – 250 k miles) without serious problems. Those used more urbanly or aggressively will need investment after 200,000 km (125 k miles), but generally still exceed 300,000 km (185 k miles) without fatal defects.

2.5 l TDI V6 EA330 diesel Engines

The largest and most powerful diesels fitted to the Audi A6 C5 are the 2.5 l TDI V6 of the EA330 family. These are presented here in two generations: generation A (engine code AFB, AKN, AYM, AKE) and generation B (engine code BFC, BCZ, BDG, BDH, BAU).

These are units with a cast iron cylinder block, two aluminum cylinder heads and a timing belt. Each of the cylinder heads has two camshafts, in total there are 24 valves and there are hydraulic compensators. The injection is direct with a Bosch VP44 high pressure pump.

EA330 generation A 2.5 l TDI engines may have problems with the camshafts (cams and rocker arms wear out too quickly). After 220 – 250,000 km (135 – 155 k miles) the high pressure pump may fail (even earlier if low quality diesel is used). These two weak points are the most famous and expensive ones to repair.

Among the less serious problems we have the crankcase ventilation system filter which becomes clogged and requires periodic cleaning. The flowmeter is not too long-lived. At high mileage, oil leaks may appear at the point of contact between the block and the sump or from under the valve cover.

Around 150 – 200 thousand km (95 – 125 k miles), the turbine geometry adjustment system can get dirty and block.

In 2003, generation B appeared and brought about important changes. First of all, the problematic timing mechanism has been updated: here the cam of the camshaft presses on a roller bearing. This choice has made it possible to increase the life of the rocker arms.

The BFC engine, while theoretically part of generation B, still has the old type of distribution, so in fact it can be seen as a generation A engine.

Otherwise the same weaknesses remained. However, there may be some cases when the modernized camshafts burst (even at mileage of 150 – 250 thousand km or 95 – 155 k miles).

All 2.5 l TDI engines love high-quality oil and its frequent replacement. Bad oil contributes to the wear of the hydraulic compensators and worsens the operating conditions of the camshafts.

Despite all the weaknesses, it must be said that engines treated well have a decent life. Generation A aggregates should live at least 250,000 km (155 k miles) without fatal defects, while those of generation B can even exceed 320,000 km (200 k miles) without major failures.

Petrol/Gasoline Engines

1.8 l EA827 Engines

The smallest petrol engines fitted to the Audi A6 C5 are the 1.8 l of the EA827 family. This is a very old family of engines and the engines fitted here are part of the latest generation of this series, which technically represent a transition from the old EA827 to the new EA113. They are available in the 125 HP naturally aspirated version and the 150 – 180 HP turbo (1.8 T) version.

On naturally aspirated version, the timing belt must be kept under control, if it breaks the valves will be damaged. The mechanics recommend replacing it every 60,000 km (35 k miles) as there have been cases where it failed to reach the declared 90,000 km (55 k miles). The hydraulic tensioner / phase shifter which ensures the correct functioning of the chain that connects the camshafts also often fails. Not even the oil pump can be defined as too long-lived.

The crankcase ventilation system can become clogged, the oil separator can freeze when temperatures are very low. There may be power losses due to dirty intake system. Rough running is often due to dirty injectors. There may be failures of the fan, the coolant pump and the flowmeter.

The 1.8 l petrol engine without turbine can only be of interest to someone who loves quiet driving and is never in a hurry. The engine is too weak to move the heavy Audi A6 C5 quickly.

The 1.8 l T turbo behaves better from the point of view of performance. Various types of turbines can be found on these, they can be of the KKK K03-005, K03-029/073 or K04-015/022/023 series and the power varies according to these.

The life of the turbine is usually around 150,000 km (95 k miles). If treated well, however, it can even go 200,000 km (125 k miles). The short life of the turbine is often caused by the clogging of the channel that supplies it with oil. This can happen due to poor maintenance or the wrong style of use. In addition, the turbine can suffer greatly from a clogged catalytic converter.

Despite all the weaknesses, the 1.8 l engines are quite robust in principle and generally live more than 300,000 km (185 k miles) without fatal defects.

2.0 l EA113 Engine

The 2.0 l EA113 engine is very similar to the smaller 1.8 l. Here too the distribution system is combined with a belt and chain. The chain should be changed every 180,000 km (110 k miles), but it is better to anticipate and change it at 120,000 km (75 k miles) to avoid problems. The timing belt, on the other hand, needs to be replaced every 60,000 km (35 k miles) to be on the safe side. Together with the distribution it will be better to also change the coolant pump. The latter doesn’t live very long and can give way at the least suitable moment, so it’s better to prevent.

The most famous problem with this engine is the large oil consumption. In second place are the problems with the hydraulic tensioner / phase shifter which ensures the correct functioning of the chain. If this gives way, typical knocking noises will be heard when starting the engine.

On engines of the EA113 series there can also be problems with the control unit, oil leaks, malfunctioning crankcase ventilation (the channels are cracked and the impermeability is lost), fouling of the throttle valve and rough idling. The oil pump and oil pressure sensor do not last forever.

For the rest, these aggregates are basically very robust and live at least 300,000 km (185 k miles) without fatal failures.

EA835 V6 Engines

All 6-cylinder engines fitted here are EA835 series V6s. These are presented here in different displacements and versions: 2.4 l, 2.7 l turbo, 2.8 l and 3.0 l.

Each engine has its own particularities which we will discuss later. However, there is a problem common to all these engines (which actually also applies to the large 4.2 l engines). On the Audi A6 C5 the space under the bonnet does not allow all the work to be carried out for the 6 and 8-cylinder engines. Due to the large dimensions, to carry out certain interventions it is necessary to remove the entire front part of the car (bumpers, lights, grille and more).

2.4 l V6 30v EA835 Engine

The smallest V6 in the EA835 family is the 2.4 L. They are very reliable units, and the main weak point is leaks of both oil and coolant. Generally, there are leaks from the cylinder head and spark plug wells. If the engine is overheated, losses increase dramatically.

Here, too, you have to pay attention to the combined distribution system. You have to keep an eye on the chain that joins the camshafts and you have to replace the timing belt in time, the life of which is not very high.

If low-quality oil is used or it is rarely replaced, there will be accelerated wear of the hydraulic compensators and chain tensioner. With high mileage, problems with the electrical part may appear: sensors, ignition coils and lambda sensors. Rough idling is often caused by a dirty throttle valve.

Thanks to their great robustness, well-maintained engines live around 330,000 km (205 k miles) without fatal failures.

2.7 l V6 30v Turbo EA835 Engine

The only turbocharged engines in the EA835 family are the 2.7-litre V6s. They are relatively complex engines, but offer good performance. The greater complexity requires more attention from the owner. First of all, the cooling system must always be kept in good condition as these are very hot engines that can easily overheat. The coolant pump and thermostat do not demonstrate great reliability and durability.

Oil leaks are encountered quite often. Impermeabilityleaks that cause unnecessary air to penetrate are not uncommon.

Turbines don’t always have a long life. On average, they live around 150,000 km (95 k miles), but there are also cases where they “die” at around 100,000 km (60 k miles). If well treated they can live even more than 200,000 km (125 k miles). The probability that the oil channels going to the turbines become clogged is relatively high and this obviously causes their accelerated wear. This can happen due to poor maintenance or the wrong style of use.

Even the intake in bad condition does not extend the life of these aggregates, so you have to keep an eye on it. Another bad part is that the turbines are hidden at the bottom and therefore difficult to control.

Here too it is advisable to replace the timing belt every 60,000 km (35 k miles) to prevent it from breaking which damages the valves. The chain, on the other hand, should be changed every 120,000 km (75 k miles). A lot of attention is also needed for the ignition system and in particular for the not too long-lived coils.

In this case we cannot call the engine too reliable. Serious problems can usually appear after 200,000 km (125 k miles).

2.8 l V6 30v EA835 Engine

The 2.8 L V6 EA835 engine is very similar to its smaller 2.4 L sibling. The increased displacement allows for better performance to be offered, but it must be said that fuel consumption is approximately the same and maintenance costs do not increase too much.

The weaknesses, possible problems and durability of this aggregate are similar to those of the smaller brother that we have covered above.

3.0 l V6 30v EA835 EVO Engine

The largest engine in the EA835 family is the 3.0 L. It is actually part of the EA835 EVO which is the latest generation of this series. The peculiarity of these aggregates is the aluminum block, the phase shifters in the intake and exhaust and the bad reputation they have obtained over time.

The 3.0 l engine is quite recent and was also mounted on the following generation Audi A6 C6 on which it is considered the most reliable of the petrol engines. On the Audi A6 C5, on the other hand, it is no more reliable than the other engines, on the contrary, it has received a bad reputation. It is true that it can be capricious, but it must be said that it presents serious problems only if he is treated badly. Basically it’s a good aggregate, it has good torque and good power, it’s not so noisy and it’s pleasant in general.

The main weakness is the short-lived ignition coils which fail relatively often. Even phase shifters have a short life span and can fail even every 100,000 km (60 k miles). Less serious problems also occur such as the failure of some sensors or the malfunction of the crankcase ventilation system.

At high mileage it will need to replace the intake manifold gasket. Oil leaks happen as well as on smaller engines.

In no case should you allow this engine to overheat, otherwise you risk the appearance of cracks on the cylinder block, the destruction of the cylinder walls, a radical increase in oil or coolant leakage.

Engines treated well turn out to be quite robust and can live 350 – 380 thousand km (220 – 240 k miles) without fatal failure.

4.2 l V8 40v EA824 Engines

The largest and most powerful engines mounted on the Audi A6 C5 are the 4.2 l V8s of the EA824 family. These can be naturally aspirated or bi-turbo (for the sporty RS6 versions).

These are quite reliable engines (as much as possible on a sports car with impressive powers). Despite the aluminum cylinder block, destruction of the cylinder walls is rarely encountered. However, this is very likely if poor quality oil is used, if the oil is rarely changed or if the engine overheats.

In general, the 4.2 l V8 engine (like the 2.7 l turbo) is at risk of overheating and therefore you need to pay close attention to the temperature, the various sensors and the cooling system in general.

The distribution has both the belt and chains at the same time. The most frequent and widespread problem is the failure of the chain tensioners. The belt must be monitored constantly and replaced in time, if it breaks the valves will be damaged.

Oil leaks are also encountered on this engine (even greater than on smaller engines). It usually occurs at the point of contact between the engine and gearbox.

Conclusions and Advice & Tips for buying used

The Audi A6 C5 is a premium German sedan that can now be found at a low price today. It offers a lot of comfort and driving pleasure, but it can also have many flaws if you find an example in bad condition. Generally it shouldn’t give major problems before 200,000 km (125 k miles) and in fact they live up to 250 – 300,000 km (255 – 185 k miles).

You have to be very careful about the mileage when buying a used Audi A6 C5 as it is very easy to lower the mileage. You will need to pay attention to the state of the interior to understand how many kilometers the car has. The first serious signs of wear will be seen after 200,000 km (125 k miles). So if you see an Audi A6 C5 with broken seat and steering wheel upholstery, but it says 120,000 km (75 k miles) on it, then the mileage has almost certainly been lowered.

The main competitors of the Audi A6 C5 are: Audi A6 Allroad C5, BMW 5 Series E39, Mercedes-Benz E-Class W210, Volvo S80, Volvo S60, Lexus GS and other similar cars.

The most important thing is to find a car in good general condition.

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