After the first generation of the Audi A6 model (body C4 / 4A) ceased production in 1997, the reliable AAT and AEL inline turbodiesels with 2.5-liter displacement and 5 cylinders, as well as the well-known 1.9-liter turbodiesel engine with 4 cylinders and index 1Z were also discontinued.
The new-generation Audi A6 (C5 / 4B body) used an inline four-cylinder 1.9-liter engine and its 2.5-liter six-cylinder V-twin counterpart.
Audi EA330 A-series 2.5 TDI diesel engines
Audi EA330 A-series 2.5 TDI engines are V6 diesel engines with direct fuel injection. The main engine models in this series include AFB, AKE, AKN and AYM.
Main characteristics of EA330 A-series 2.5 TDI engines:
| Characteristics | Value |
|---|---|
| Working volume | 2496 cm³ |
| Cylinder bore × piston stroke | 78.3 × 86.4 mm |
| Number of valves | 24 |
| Injection type | Direct injection |
Models of EA330 A-series engines:
| Model | Valves | Injection | Power | Torque | Application |
|---|---|---|---|---|---|
| AFB | 24V | Direct injection | 150 hp | 310 Nm | Audi A4, A6, A8 |
| AKE | 24V | Direct injection | 180 hp | 370 Nm | Audi A6, A8 |
| AKN | 24V | Direct injection | 150 hp | 310 Nm | Audi A4, A6 |
| AYM | 24V | Direct injection | 155 hp | 310 Nm | Audi A4, A6, A8 |
Audi EA330 B-series 2.5 TDI diesel engines
Audi EA330 B-series 2.5 TDI engines are a later and improved version, featuring improved performance and environmental performance.
Main features of the EA330 B-series 2.5 TDI engines:
| Characteristics | Value |
|---|---|
| Working volume | 2496 cm³ |
| Cylinder bore × piston stroke | 78.3 × 86.4 mm |
| Number of valves | 24 |
| Injection type | Direct injection |
Models of EA330 B-series engines:
| Model | Valves | Injection | Power | Torque | Application |
|---|---|---|---|---|---|
| BAU | 24V | Direct injection | 180 hp | 370 Nm | Audi A6, Allroad |
| BCZ | 24V | Direct injection | 163 hp | 310 Nm | Audi A4, A6 |
| BDG | 24V | Direct injection | 163 hp | 350 Nm | Audi A4, A6 |
| BDH | 24V | Direct injection | 180 hp | 370 Nm | Audi A6, A8 |
| BFC | 24V | Direct injection | 163 hp | 310 Nm | Audi A6, Allroad |
These engines show powerful performance for their time, delivering high torque and power, making them a popular choice for Audi cars.
The 2.5 TDI powertrain is the first V-block diesel to get four valves per cylinder. The V6 turbodiesel utilizes:
- the proprietary TDI direct (direct) fuel injection system;
- turbocharger with variable geometry system (VTG) and intercooler;
- electronically controlled distributor-type fuel injector with radial plungers and a control
- electromagnetic valve.
In addition to Audi, the 2.5 TDI V6 engine was installed on the VW Passat and on the Skoda Superb.
The first in the line of new power units was the AFB motor with an output of 150 horsepower. Diesel Audi A6, equipped with this motor, overcame the ten-second barrier in a sprint from zero to one hundred km / h (acceleration in 9.7 s) and developed a top speed of more than two hundred km / h.
A little later, the AFB engine was paired with a similarly powerful AKN unit.
At the end of 1998, a 2.5-liter turbodiesel engine with an output of 180 horsepower and a high torque of 370 Nm, available already at 1500 rpm, was released. This power unit with the factory index AKE for those years became the flagship turbodiesel not only Audi, but also the entire concern VAG. Therefore, the production continued for 7 years, production was stopped only in 2005.
In parallel with it from 2003 and until the end of production of Audi A6 C5 in 2005, turbodiesels BAU and BDH of similar capacity were produced.
In 2001, a version of the 2.5-liter turbodiesel motor (factory index AYM) with 155 horsepower was released. And a year later, from the middle of 2002 to the middle of 2003, the BFC power unit with an output of 163 horsepower was produced.
In 2003, a 160-horsepower BDG engine appeared. A year later, a similar in power turbodiesel BCZ was launched. All three power units were produced until the end of production of Audi A6 of C5 generation.
Problems.
Hydrocompensators and timing faults
Faulty hydrocompensators are signaled by a characteristic metallic knocking noise that progresses over time and can be heard even when the engine is running at operating temperature. Although at first only a couple of hydraulic tappets knock, it will be necessary to replace all of them. The cost of one hydrocompensator is about 4-5 dollars. But their number can reach several dozen, because of which the replacement will cost a considerable sum.
Kits for the restoration of parts of the cylinder-head of the engine 2.5 TDI V6 are still in demand. On the photo: a set of camshafts, rockers and hydrocompensators for the A-series motor.
Replacing the timing belt
Even a routine replacement of the timing belt will also cost a couple of hundred dollars. It is recommended to do this after 120 thousand kilometers of mileage for the first time, further – after 90 thousand kilometers of mileage. It is quite difficult to change the timing belt: due to the fact that the engine compartment is very tightly placed, you have to remove the bumper, radiator, intercooler and even headlights. A complete set of spare parts for replacing the timing belt includes four rollers, cooling system pump (water pump) and two timing belts (timing belt and fuel injection drive).
When changing the timing belt, you will need a set of special stoppers to hold the crankshaft, camshafts, and fuel injector. You will also need a VAG-scanner for further checking and, if necessary, for correction of the injection advance angle.
Together with the timing belt it is necessary to change the cooling system pump driven by it. Moreover, the water pump for replacement should be of very high quality, and better – original (the manufacturer’s restored “X” pump will do). Saving on a set of spare parts for servicing the timing mechanism is not recommended categorically – in case of collision of valves and pistons due to jamming of the pump and breakage / shearing of the timing belt there is damage to valves, destruction of pistons, and often the light alloy cylinder head itself!
If the driver uses only quality spare parts, the cost of repair of turbodiesel V6 after a “friendly meeting” of valves and pistons will be very unpleasantly surprised, and therefore, it is often cheaper to buy a contract motor second-hand, rather than to restore your own.
All parts of the timing drive are available in quality “non-original” and they can be used quite well. However, in this case the cost of belts and a set of rollers also “bites”: 200-250$ for a set consisting of “ContiTech” belts and “INA” rollers is quite common.
To service the timing drive it is necessary to dismantle the whole front end of the car.
It is necessary to use a quality water pump in the engine. After all, replacement of the cooling system pump in case of its leakage is equal in cost to replacement of the timing belt. During scheduled maintenance of the timing system it is recommended to change and cheap (8-10$) thermostat of the cooling system. Due to the design features of the engine, replacement of a broken thermostat, as well as in the case of the current pump, will be similar in scope of work and their cost to the replacement of the timing belt.
Oil leaks on 2.5 TDI engines
In 2.5 TDI engines, oil also leaks on the mating planes of the cylinder head and the block itself. The reason is overheating of the power unit. There are several reasons for overheating: rare replacement of antifreeze, use of low quality oil, and wear of rubber gaskets and motor oil seals.
Problems most often occur precisely at the junction of the cylinder head and valve covers. Often oil “floats” from under the oil filler neck. The cause of such problems – clogged resinous deposits crankcase gas filter (by the way, deposits appear precisely because of cheap oil or rare replacement). The problem will be solved either by replacing the filter with a cyclone-type filter, or simply washing the filter.
To eliminate leaks from under the valve cover gaskets, they must be replaced. To the drivers’ dismay, the rubber gaskets of valve covers, as well as the rubber grommets of injection nozzle holes are one part with the cover itself, the price for which is not insignificant. After a mileage of 30,000 – 40,000 kilometers, it is enough to use an engine sealant.
The problems of the turbodiesel place do not end here: malfunctions occur with the joint of the cast-iron cylinder block with the crankcase pan. Leakage occurs because the block and the pallet are made of different materials, with different expansion of metals, and when heated, the connection “block-pallet” becomes movable.
It is worth remembering that the oil pan can be damaged when the car collides with obstacles, the reason is its low location.
It is undesirable to overheat the motor: the mating of the cylinder-head-block will suffer immediately.
Frequent malfunctions of V6 2.5 TDI motors
Quite popular opinion that V6 2.5 TDI power units of the “A” series are unreliable, unfinished and with a number of errors. They honestly “work” under 150-200 thousand kilometers, after which there are a number of problems. For example, there comes the time of wear of components of the timing system in the cylinder-head: it is necessary to change rocker arms with washers, hydrocompensators of valves.
It is believed that this is due to lack of oil in the upper part of the cylinder-head due to the use of cheap oil and its infrequent replacement. Confirmation of this is the rapid wear of the timing gear in cars that used “synthetics” with an extended oil change interval.
If you use cheap and unsuitable oil and change it less often than once every 15 thousand kilometers, the oil channels in the block head may become clogged. The result is oil starvation: the oil pump will not deliver the right amount of oil to the top of the cylinder head at low speeds. Without oil, the rockers and hydrocompensators are poorly lubricated and wear out quickly. Then the camshafts themselves wear out.
The engine is designed as follows: the friction pair “rocker – camshaft cam” uses lubricant from hydrocompensators, which comes through the oil channel inside the rocker. If the hydraulic tappet sags due to heavy wear, the gap between the head and the rocker becomes larger by a couple of millimeters: this is enough to prevent oil from entering the rocker channel and splashing over the head of the hydrocompensator.
The rocker arm surface as well as the cam of the camshaft becomes fouled. When the wear becomes critical, the washers can fall out and the hydrocompensator can fail. The rocker will fall out, the valve will not open, which will eventually lead to very sad consequences: the rocker, caught in the valve mechanism of the neighboring cylinder or in the helical gears of the camshaft, becomes the cause of failure of various elements of the engine, up to complete failure. But the engine does not send warnings about the forthcoming “accident”: the breakdown happens suddenly. Therefore, drivers are advised to check the condition of the timing regularly.
If the rocker fell out and did not lead to a serious breakdown, then you should pay attention to the valves not opening: if the problem occurred with one valve, there will be no consequences. But unopened 2 valves lead to the fact that the cylinder is “shut down”. This is signaled by a drop in power of the power unit. The engine can not be used in such a state, it will have to be repaired.
The cost of repair can exceed a thousand dollars (the cost of only one camshaft can reach a hundred dollars, hydraulic pushrods – up to six dollars). If it is necessary to replace the timing belts with their rollers and water pump, the repair will cost an even greater amount, comparable to the purchase of the same contract engine.
Malfunctions of the motor 2,5 TDI B-series
As we have already realized, there were enough problems with the A-series motors. Therefore, the engines of B-series (BAU, BDG, BDH), released in 2003, received an improved timing drive. Thus, the rocker arm was equipped with a roller bearing: it is the camshaft cam that presses on it, and the wear resistance of parts has increased. The exception – BFC engines with old-type timing, because of which all the problems of A-series motors were transferred to this power unit.
The B-series units are more reliable, as there have been many new developments over the years. For example, one-piece monolithic camshafts have been replaced by lightweight cams: their cams are pressed onto a hollow steel shaft tube (by the way, such a solution was previously used only on sports power units). But there are disadvantages of such a design – the camshaft can break at very low temperatures and on engine oil with high low-temperature viscosity.
BAU engines for 180 horsepower received a cylinder block identical to the AKE motor. Because of this, it is possible to solve the problem of a worn camshaft in an AKE motor by simply buying a used cylinder head from BAU.
Motor malfunctions due to aging and mileage
With significant mileage, the cylinder piston group parts are the first to wear out. There is no specific mileage after which overhaul is required: in each engine it depends on the operating conditions and compliance with the maintenance schedule, as well as the previously mentioned oil change interval. The more “caring” the driver is, the longer the power unit will last.
The resource of the cylinder in A-series engines is less than in B-series engines. But this assessment is not absolutely correct, as A-series motors have a higher mileage due to the earlier year of production. It has been found that among the A and B series CKDs, the 150 horsepower AFB engine has the least life.
High-mileage V6 powertrains have a problem such as difficulty in replacing glow plugs: the lower part of the plugs is “stuck” in the cylinder head. It is almost impossible to unscrew the plugs: they either break or are unscrewed from the cylinder head with part of the thread. As a result, the cylinder head has to be repaired.
Service life of plugs – up to one hundred thousand kilometers, but it is recommended to check their condition after 60 thousand kilometers of mileage.
Engines with a mileage of 250,000 kilometers often face such problems as the breakdown of the control injector. The reason is the failure of the needle stroke sensor in its upper part (there are no claims to the mechanical component of the injector). Because of such a malfunction, the engine goes into “crash”, and along with the fallen power, fuel consumption increases. VAG-scanner will help to determine the problem, which will report the corresponding error. Replacement of the control injector will cost about 40 dollars for used injectors and a couple hundred dollars if you buy a new device.
Audi V6 fuel system malfunctions
In V6 2.5 TDI motors, the VP44 fuel injector often fails: its service life is about 200 thousand kilometers. Bosch VP44 pump works properly only when using high-quality fuel. Cheap fuel causes failure of the mechanical part of the fuel injection pump: the rotary pump, injection advance angle piston, as well as the parts forming friction pairs with them break down. Wear products get on the filter meshes in the pump channels, and mechanical wear of the booster becomes the cause of the fuel pressure drop in the fuel injection pump. If the pressure drops, there is a problem with the injection advance angle, because this piston is driven by fuel. Also, the injection regulator piston in the fuel injector wedges if you drive on cheap, low quality fuel.
Electrics of the fuel injector can also cause a lot of problems: for example, there are known cases of burnout in the ECU of the pump transistor key, which is responsible for controlling the valve for adjusting the volume of injected fuel. The reason is wear or overheating of the ECU, which is unsuccessfully located – on the pump housing, as well as overload caused by a jammed piston of the injection advance angle.
Problems with the ECU are signaled by the engine stalling on the move or inability to start after idle time.
The original fuel injector is sold only as a complete assembly, the cost is obscenely high. Therefore, VAG dealers offer such an option as replacement of the factory-rebuilt pump in general for the old one. But there are other options – independent restoration of the ECU of the fuel injector if you have the appropriate skills, as well as the purchase of the original used fuel injector, the cost of which is many times lower than the new one.
V6 2.5 TDI engine can also stall while driving due to a breakdown of the low-pressure booster pump. It should be taken into account that when it fails, the high-pressure pump will also require replacement.
But there are no problems with variable geometry: if you operate the car correctly and change the oil on time, then even a mileage of 250,000 kilometers will not be the limit.
Driving at low speeds negatively affects the turbine geometry blades – they get wedged, which leads to low boost pressure or “overblowing” with emergency engine operation and limited fuel supply. The problem can be solved by disassembling and cleaning the turbine geometry with nothing restricting access.
If the turbocharger has failed, this will be signaled by a disappeared supercharger and strong oil smoke. It is necessary to contact service specialists. If the unit can not be repaired, it can be replaced with a used one.
Age V6 2.5 TDI motors can burst the hoses of vacuum line, also periodically fail electrovacuum valves controlling the turbine and mechanical EGR valve. Buying a new valve will cost fifty-five dollars (for a Pierburg part). But two-spring injectors in these motors are characterized by reliability. Atomizers, if necessary, are changed separately.
Total
Engines V6 2.5 TDI can not be called millionaires, but they are not unreliable: it is enough to treat the motor with care, so that it will drive 400 000 – 500 000 kilometers without problems.