Volkswagen, like many other manufacturers, has had inlets and lows in its history, as well as very successful and total misfires. Recently, someone may suspect that the 2.0 TDI engine will go down in history as the worst drive unit of the concern, but this is not the case for users. Such an engine is still very good, but only by design, known as the 2.5 TDI V6. In this article, we will not only present the history of the failure of this engine, but also try to warn you against buying a used car powered by this unit.
Which engine in Volkswagen history is the worst? Much depends on your point of view. Of course, the 2.0 TDI unit will be a bane and a nuisance for the concern for many years to come. A few years ago it spoiled the brand image in the TDI PD version. It was an unsuccessful, poorly designed structure, but also improved, to finally eliminate it from the market. Contrary to fate, it was the most successful version of this engine, the EA189, which brought the biggest losses to the concern and embarrassed the German giant.
However, users don’t really care. That is why I do not consider the 2.0 TDI the worst engine ever, as the customer’s point of view is completely different. The “first league” includes 1.4 TSI and 1.8 TSI engines, which can ruin the car owner’s budget. Interestingly, the flawed 2.0 TDI PD is not as much of a monster as it might seem.1.9 TDI units can be the nightmare of the owner. We, however, consider the 2.5 TDI V6 engine to be the real devil, for several reasons.
- First of all, it is a very tempting power unit, providing excellent performance even for large cars. All thanks not so much to the power (minimum 150 HP), but to the torque, which, depending on the version, reaches a maximum value from 310 to 370 Nm. This is enough to give the appropriate dynamics to a large sedan or station wagon such as the Audi A6 or Škoda Superb, with still low fuel consumption.
- Second, the operating culture of the V6, despite being Diesel with a distributor pump, remains high. Compared to the very popular 1.9 TDI, they are two different worlds.
- Third, the average Kowalski buys “prestige” in the form of a V6.
- Fourth, in some models, for example the Audi Allroad, the 2.5 TDI engine seems to be the only sensible power unit, as gasoline engines will be fuel-consuming.
- And fifth, aftermarket prices are very low.
To sum up, we get a very interestingly configured car at a low price, in addition with a higher standard of equipment, often with an automatic transmission. At the same time, we get a real Pandora’s box, which, when opened, wreaks enormous havoc on the owner’s account. Whoever has dealt with this unit knows that it is the real devil.
2.5 TDI History
If you go back to the very beginning, the history of the 2.5 TDI engine goes back further than the 1.9 TDI. It’s just that in the 1980s a five-cylinder engine with such a capacity made its debut and it may be confused with the newer V6. In fact, the V6 is the successor to the R5 and only made its debut in 1997.
Inline engines were left on some delivery and passenger models, and they were offered even longer than our hero V6. It is worth noting here that the 2.5 TDI R5 engine has nothing to do with the infamous V6. This is a very successful engine that is difficult to object to.
The 2.5 TDI V6 was introduced in the Audi A6 as an alternative to the six-cylinder petrol engines. It caused a very positive feeling, it was highly praised in tests and by car owners. And that was just the beginning. There were even more powerful variants (180 HP), they were completed with Multitronic automatic transmissions, giving even better performance – by the way, they are as unfortunate transmissions as the engine itself.
In 1998, the unit also went to the smaller Audi A4 of the first generation and the Volkswagen Passat B5, and four years later also to the Škoda Superb. Fortunately, it did not go under the hood of vehicles other than those belonging to the VW group.
2.5 TDI Specs and Construction
The 2.5 TDI engine described is a V6 with a 90 degree split angle and a total displacement of 2,469 cc. The compression ratio is relatively high compared to today’s standards, at 19.5. However, the design of the R5 had a compression ratio of as much as 21, although the later version was lowered to 18.5. A cast iron engine block is connected to aluminum cylinder heads and an aluminum sump. There is an oil pump in the bowl, driven by a chain, which also transmits power to the balance shaft.
Two overhead camshafts are mounted in the head, which actuate four valves per cylinder. The clearance is adjusted hydraulically. The intake valve shafts are driven by a long toothed belt, while the exhaust valve shafts are gear-meshed with the former. An additional belt drives the injection pump located at the front between the heads. All engines were mounted longitudinally.
Technically, the 2.5 TDI V6 engine did not have any innovative solutions and fireworks. Even the injection system prepared by Bosch remained conventional, as in the older R5, consisting of classic injectors (direct injection) that received fuel directly from a distributor injection pump with a rather advanced radial design.
Although VW / Audi used unit injectors in the 1.9 TDI unit at that time, such elements were not fully introduced into the V6 engine. The newer 2.7 TDI and 3.0 TDI units already have Common Rail injection. A turbocharger with variable geometry takes care of the right dose of air.
The 2.5 TDI V6 engine was available in several power levels and of course you can meet its various markings. The first was the AFB and AKN unit with 150 HP and 310 Nm of torque. Soon after, the top version of this engine with 180 HP and 370 Nm of torque, AKE, BDH, BAU, and later also BND, debuted. Both engines achieved their maximum torque at 1,500 rpm.
It was different in the case of the later 155- and 163-horse varieties. Both generated 310 Nm, but already at 1400 rpm. The weaker unit is called AYM, while the more powerful BFC, BCZ or BDG and in some models reached 350 Nm of torque. The units met the Euro 3 and Euro 4 standards (BDG and BDH). It was only in the latter engines that a device known as the EGR valve appeared. The engine was discontinued due to the introduction of the Euro 5 standard.
Theoretically, the 2.5 TDI V6 was supposed to be ideal, but it turned out to be a dud.Users quickly felt the effects of the manufacturer’s shortcomings on their own skin. The company supposedly introduced corrections and eliminated some flaws, but looking from today’s perspective, for 10 years the engine has not been improved enough to recommend any of its variants.
The biggest problem of the 2.5 TDI engine was that the simple structure, which theoretically should withstand hundreds of thousands of kilometers of mileage, was not well thought out, adapted to the then operating conditions and the skills and knowledge of users. Volkswagen did not take care of checking the durability of individual elements and this resulted in serious and very expensive breakdowns. You will read about failures and problems as well as their causes and effects tomorrow in the second part of the article.
2.5 TDI Problems & Reliability
In the first part of the article, you learned a lot about the history and construction of the 2.5 TDI V6 engine. You already know its structure and advantages, and in this material you will only know its disadvantages.
- Problems Often Occur In Decreased Power
- Problem With the Lubrication System
- Problem With the Camshafts
- Problem With the Injection Pump
- Problem With the Turbocharger
- Problem With the EGR Valve
- Problem With the Dual Mass Flywheel
As you could read in the first part of this article, at the very end of this article, the engine was not prepared for the operating conditions of the time. There is a lot of talk and writing about the failure of this unit, but no one mentions that the 2.5 TDI V6 made its debut in the worst possible period for a diesel. It was a time when new-generation diesels appeared in passenger cars.
The Common Rail injection system was not yet known, and even the turbo diesel engines did not impress with performance. Only units appeared that could guarantee good performance, comparable to gasoline units of the same capacity. In the year of the engine’s debut (1997), Fiat was the first to introduce Common Rail injection, and other manufacturers were just starting out on the subject. The first TDI engine with unit injectors appeared in 1998.
Let’s be honest – the unit offered by Audi was a complete novelty for many people, something that the customers of this brand did not know. What’s more, people who have got used to very durable Volkswagen diesels from earlier years – for example, the 2.5 TDI R5. There were no articles in the automotive press every two weeks on how to drive a diesel engine so that it would not cause trouble or how to care for a turbocharger, because there was no need for it.
At the end of the 90s, nobody expected that diesels, these clunky machines that cannot be driven over, need special care. In addition, the quality of the diesel fuel was not controlled as it is now at many filling stations. Nobody complained about it, because the clunky 2.5 TDI R5 or 1.9 TDI burned out almost everything. And this, along with the faulty design of the TDI V6 engine, only accumulated problems, and there were many of them.
Problems Often Occur In Decreased Power
Today we are used to the fact that the power and torque values of modern diesel engines provided by the manufacturer are usually understated. Especially in the range of TDI units, where on the dynamometer it turns out that we have an additional 10-15 HP under the hood. This was not the case at the end of the 90s. The 2.5 TDI V6 engine usually did not reach the values specified by the manufacturer, although the dynamics and work culture he offered were impressive.
Unfortunately, this was not the biggest problem for users who, after a mileage of 150,000-200,000 km cursed the abbreviation TDI. Already, or maybe as much as, because many first owners often never touched the problem of a faulty engine.
Today, no one is surprised by the first symptoms of the depletion of modern engines at a mileage of 200,000 km. It’s just that even modern engines can be repaired or simply taken care of, and many of the disadvantages of the 2.5 TDI V6 could not be removed, while the special care for the engine did not always help.
There was a problem with the Lubrication System
The most serious and having the greatest impact on the failure rate of the 2.5 TDI V6 engine is the faulty lubrication system, not the wearing camshafts as is commonly believed. It is he who causes most of the troubles of users of this engine.
A minor problem with 2.5 TDI, but having an impact on proper lubrication, is the clogging of pneumothorax and the lack of ventilation of the crankcase, which may also cause rapid destruction of the turbocharger. However, breakdowns of the oil pump, and more specifically its drive, are more severe.
As I mentioned in the first part of the article, the pump that distributes the oil is driven by a chain that also connects it to the balancer shaft. The pump is placed in an oil pan. The chain is stretched over time by a poorly thought-out tensioner, which causes the teeth to be rubbed on the sprocket.
If a fault is noticed in time, it will help to eliminate this phenomenon, but usually the first signs (no oil pressure) appear only when it is much too late. Effect? Most of the problems described below, mainly those with the camshafts and the turbocharger. The worst effect, which is already irreversible, is the seizure of the drive unit. Repair is unprofitable.
- Symptoms: after 150,000-200,000 km: Lubrication indicator light comes on with proper oil level, turbocharger seized.
- Repair: Usually it’s too late to repair, but sometimes you notice a problem sooner. Depending on the damage, the cost of repair is $39-$130. When the engine seizes up, it is not worth repairing.
There is a problem with Camshafts
With all the disadvantages of the 2.5 TDI V6 engine, the camshafts that are made of too weak material are most often mentioned. The truth is, an indirect cause of shaft problems is poor lubrication and user-used engine oils that are changed too rarely. Another thing is that with such a design of the timing drive (high pressure on the cams of the cams) Volkswagen should use a better material.
The question remains: has the 2.5 TDI engine not been tested or has the problem with the shafts simply been ignored? This question does not arise without a reason, because the problem with shafts applies to virtually all engines at the beginning of production and usually appears from around 150,000 km mileage. Later, the concern introduced changes that at the very end almost eliminated problems with the timing system. It’s just that almost, not completely.
The most vulnerable to damage to the camshafts are power units manufactured in 1997–2001. Not only were the cams worn, but also the valve levers, and the hydraulic regulators refused to cooperate, further complicating the matter.
This is the result of bad materials used by the manufacturer, but also partially problems with the lubrication system. Taking into account the fact that the manufacturer initially used oil intervals of 15,000 km, so quite reasonable, we definitely have the culprits – the designers and the research department.
After 2001, new timing components were introduced. Tappets and valve levers proved to be more durable, and so did the shafts, but sometimes they break (too hard material?). According to some mechanics, cracking is the result of extending the oil intervals to 30,000 km.
In their opinion, users who change oil every 15,000 km had no problems with the timing after 2001. The problem with the rollers was eliminated for good only in the years of 2004, although it happens occasionally that one of the rollers breaks. Apparently, the end-of-production BDH variety is not exposed to failures in the timing system.
Another issue is the costly replacement of the timing gear. Parts prices are still relatively affordable. A set of all elements of a good company costs about $205. Unfortunately, the operation is time-consuming and requires the front of the car to be dismantled.
- Symptoms: after the course of 150,000–250,000 km: Metallic knock from under the valve cover, also heard when the engine is under load, engine runs erratically, problem with starting it.
- Repair: replacement of rollers with new ones or their regeneration. The cost of about $1026-$1540. Replacing the timing drive with parts about $515-$770.
There was a problem with the injection pump
Another element that can spoil the blood of users of the described 2.5 TDI engine is the VP44 injection pump. This is where the failures of the control electronics and the fuel dosing solenoid valve most often occur. Unfortunately, the cause is usually low-quality fuel. It is also the fault of the radial structure, which theoretically works very precisely, unfortunately was not the best solution at that time.
The pump was improved in terms of durability in 2001 with the timing system, but its design is even more complicated and more difficult to repair, especially in engines that meet the Euro 4 standard, but still quite delicate and sensitive to fuel quality.
- Symptoms:after the course of 150,000-200,000 km: uneven engine operation, problem with spinning in, smoking from the exhaust pipe.
- Repair: repair of control elements, replacement or regeneration of a damaged / worn pump. The cost is about $257-$1540.
There is a problem with the turbocharger
This is another part of the puzzle, which is a domino effect that begins with a faulty lubrication system. The problem with lubrication first of all affects small and delicate parts, heavily loaded and hot. And what else better meets these conditions than a turbocharger? It will refuse to obey before the user or mechanic notices a problem with the lubrication system.
So it’s a good sign that you should take care of the oil pump and blow it up before the 2.5 TDI engine seizes up. The design of the turbocharger itself is not flawed, but at the end of the 90s, users did not know much about its proper operation, i.e. cooling after intensive driving and warming up before it.
- Symptoms: turbocharger leaks, no engine power, blue smoke from the exhaust pipe, whistling when accelerating.
- Repair: replacement of the element with a new or regenerated one. Replacing the intercooler and cleaning the intake system, checking and replacing the turbocharger oil supply and discharge pipes. The new Garrett turbocharger (original) costs about $514. Alternatives are sometimes cheaper or more expensive. The cost of repair with the replacement of the turbocharger for a new one should be around $1026.
There is a problem with the EGR
The EGR valve appeared at the end of production in engines meeting the Euro 4 standard. As in every engine with an EGR valve, there is also a problem with this element in some variants of Volkswagen diesel. Fortunately, this is the least trouble for users. It is worth cleaning the valve every two or three oil changes. When it breaks down, it must be replaced.
- Symptoms: from 150,000 km: exhaust smoke, poor gas response, no power, problematic engine start.
- Repair: cleaning or replacement with a new one. The cost of the new part is about $154.
There was a problem with the Dual Mass Flywheel
Unfortunately, another element that draws money from the pocket of the owner of a 2.5 TDI car is the dual mass wheel. This unit was equipped with them if it was mated to a manual gearbox. Caring for this element will extend its life. It is not an excessively fast wearing part.
- Symptoms: engine vibrations, metallic knocking, stiff gear changes, jerking when accelerating.
- Repair cost: the wheel itself costs from $385 to $515 depending on the manufacturer and engine version. A clutch costs from $90 to $205, a thrust bearing about $13. Labor from $77 to $154.
2.5 TDI Factory Service Recommendations
- Oil change – every 15,000 km (every 30,000 km long life oil), 5W-30 oil [we recommend changing no later than 15,000 km regardless of oil and service recommendations]
- Timing drive replacement – every 120,000 km [every 60,000-80,000 km recommendations]
- Replacement of the accessory drive – as needed, inspection at the oil service [including the timing drive recommendations]
- Fuel filter replacement – every 30,000 km
- Air filter replacement – every 60,000 km [every 30,000 km recommendations]
Why was the 2.5 TDI V6 a curse? Not only because it was faulty and buggy, but of course this is the overriding problem. Another thing is that unauthorized mechanics did not have the ability to diagnose problems and fix them quickly.
Even today, some of the blame for troubles with this engine can be attributed to both the mechanics and the users themselves, who want to save money. No wonder, because repairs are expensive anyway, but if properly carried out, they cost even more. Suffice it to mention the turbocharger.
Yes, it is relatively cheap, but many people decide to regenerate for $257 to make it even cheaper, and unfortunately not every workshop can professionally deal with a turbocharger with variable geometry. Another topic is intercooler replacement (from $154) and cleaning the intake and lubrication systems.
This is where the 2.5 TDI engine should be flushed. For this set of gaskets and replacement of some oil lines. Not every workshop does it, not every user can afford it. Professional, art-compliant replacement of a new turbocharger costing $515 should amount to approximately $900-$1026. This is exaggerated for many users. A “clever” mechanic can fix the problem for half that amount.
The way of exploitation is another matter. Not everyone knew in the 90s that the turbocharger should be cooled down after dynamic driving and warmed up after starting the engine. And this one encouraged dynamic driving as early as possible.
The 2.5 TDI engine is also a mechanic’s curse. Just look at how tightly it is packed, especially in mid-range models. You have already read about replacing the timing gear, but any work on the engine in the middle of its height is a big problem. For example, replacing the mounting pads can be very time consuming.