TDI Engine Failure: Core Melt Explained

Hello everyone,
Today, I had the opportunity to inspect a rebuilt 3.0 TDI engine that had been taken out of an A4 B7.
Unfortunately, it has engine damage. All the pistons in the first cylinder bank are completely melted. The valves are partially perforated, like Swiss cheese. I suspect the second cylinder bank looks similar.
Laufleistung 160.000 km. No tuning.
I'm worried that my BPP (2.7) might end up the same way. What could have caused that?
The workshop foreman suspects that the faulty injectors are the cause.
Please take a look at the pictures.

Bekanntes Bild, da wurden über ein längeren Zeitraum die Klappen für die Füllkanäle nicht oder nur teilweise geöffnet. Siehe also:

Okay, I'm ready. Please provide the German text you want me to translate.

Okay, I understand.
Can the swirl flaps be checked in any way? And what happens if you set them to "permanently open"?

Is there a way to suppress the error message that the valve actuator is causing with its plastic levers?
Perhaps someone has already done something similar before...

And when are the flaps actually closed, other than when the engine is turned off?
Shouldn't the airflow sensor have detected that not enough air was flowing?

Please excuse the many questions.

Hi,

Quote:

And when are the valves actually closed, other than when the engine is turned off?

You might be confusing the throttle valve (also known as the intake valve) with the swirl valves.
Each cylinder has 2 intake channels, and the swirl flaps close (or do not close) one of them for each cylinder. The swirl flaps should only be closed at low load.

Quote:

Shouldn't the airflow sensor have noticed that not enough air was flowing?

Here are some things that come to mind spontaneously:
- Mass airflow sensor.
- The ratio of air mass to boost pressure is incorrect.
- Lambda values
- Are there any position sensors for the swirl flaps?

Some engines only use the boost pressure (which fits the observed symptoms) or excessively high air mass readings (indicating leaks, etc.) to determine if there is sufficient airflow. My suspicion is that the engine control unit's software may have a flaw that prevents it from recognizing this specific error condition. That's unfortunate... Is the software version of the engine control unit (see Autoscan) up to date?

Best regards, Rainer.

Hello Rainer,

First, thank you for your help.
I understand the difference between the throttle valve and the swirl flaps. However, as far as I know, the swirl flaps are also closed when the engine is turned off.

If the swirl flaps are only closed under low load conditions and/or during DPF regeneration, could there be a significant reason not to leave the flaps permanently open?

Does the actuator, which moves the swirl flaps via the linkage, have to overcome a noticeable resistance in order to determine whether the "flap is open or closed"?

I would prefer to remove the flaps altogether. However, I suspect that the engine control unit will respond to this by illuminating the engine warning light. (This is based on my research so far.)

P.S. Four cables connect to the valve control units (servomotors).

Software version:

Address 01: Engine Control Unit (ECU)
Label file: DRV\059-910-401-BPP.lbl
Part number SW: 8H1 910 401, part number HW: 8E0 907 401, AL.
Part: 2.7L V6 TDI 000CG 0040
Revision: --H03--- Serial number:
Encoding: 0011181
Operating number: WSC 00672 126 64750
VCID: 60C80276B3E6013E1E-8034

However, it seems to me that the problem is more likely caused by partially worn (leaky, dripping) and also carbon-fouled injectors.

Specifically, this is a known issue with the first series of V6-CR-TDI engines, and it's precisely this type of problem that causes these kinds of damages.

The initial symptom is partial carbon buildup in some of the injector nozzle holes, which then become blocked. However, the fuel quantity/stroke doesn't change, so this is compensated for by the remaining open holes.
Holes are being injected with material, which creates a one-sided load on the needle seat (which is supposed to seal). This leads to wear and tear on the needle seat and leaks.
In Common Rail systems, where pressure is constantly maintained in the fuel rail and injector, a leaky needle valve is critical because fuel is injected even when the piezo valve is not activated.
Even if the injector tip is no longer positioned within the combustion chamber cavity, the jet still impacts the edge of the piston (at the melting points).
The temperatures are rising dramatically, even though the production cycle is complete and material is being ejected, which is causing the exhaust valves to burn out.
These engines are actually very noisy and tend to produce bluish-white smoke when idling or under light load. Replacing all the injectors with the improved version at an early stage can then save the engine.
The soot-covered intake manifold is also a result of the incomplete combustion caused by the faulty injectors.
My own 3.0 TDI engine has very few deposits in the intake manifold after a significant amount of mileage, although the injectors are fine .

Deactivating swirl flaps alters the exhaust behavior and is therefore not legal. Furthermore, they have a positive impact not only on exhaust emissions but also on other aspects.
regarding running culture, fuel consumption, and torque delivery; otherwise, the manufacturer would probably avoid such a complicated system .

Regularly reading the timing deviations in the measurement blocks using VCDS can provide a good indication of the condition of the injectors.
Therefore, it is possible to react quickly and prevent larger damages through communication and information sharing.

negatively impact.
- Mostly short distances and city driving.
- Low-quality fuel from gas stations that don't properly maintain their tanks.
- no fuel filter replacement.
- and of course, continue driving with the existing problem (smoke/knocking).

...that's all about my experiences.

Regards, Mpire.

Mpire, awesome work! Just had to say it...

I found something else related to this topic:

I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

"It states that the error message appears in 88% of cases. The faulty injectors seem plausible. Otherwise, if it were only the swirl flaps (admission valves), theoretically all the pistons should look the same. The flaps are all located on the same shaft."

My cylinder injection values are all between 0.47 mg/H and -0.38 mg/H. The intake manifold flap control for bank I and II is at 80.9% (target) and 81.3% (actual) at idle.

As long as there are no error messages and the device isn't smoking or making strange noises, can I just relax and not worry?

Hi,

The swirl flaps close at low loads for exhaust-related reasons, and serve to create a rotation of the incoming air in the combustion chamber, which improves mixing with the fuel.

Quote:

The beginning is a partial coking of individual holes in the injector tip. They are then closed. However, the amount/stroke does not change, so these are compensated for by the still open holes. Holes are injected with.

Unfortunately, that's not correct for CR injection systems. A more or less constant pressure is applied to the injector for a certain time X at the nozzle. If a hole in the nozzle tip is blocked, simply less fuel ends up in the engine.
Image 20160817_175608.jpg appears to show only 2 open nozzle holes.

As correctly described, leaking or dripping injectors can be dangerous and cause similar damage. Unfortunately, the positions and spray patterns of the nozzle holes are clearly visible in the images, and they appear uniform (20160817_175559.jpg). Therefore, I am less inclined to conclude that faulty injectors/nozzles are the sole cause.

Quote:

Otherwise, if it were only about the swirl flaps (fill flaps), theoretically all the pistons would look the same.

Yes. How do the pistons of a bank compare to each other?

Quote:

In the case of the CR (Common Rail) system, where the pressure is constantly present in the rail and the injector, a leaky needle valve is fatal, because fuel is injected even when the piezo valve is not actuated. ... Actually, these engines tend to be very noisy and produce bluish-white smoke when idling and under light load.

That's right. But who's going to drive it for that long until the pistons melt?

Best regards, Rainer.

dieselschrauber wrote:

Otherwise, if it were only about the swirl flaps (fill flaps), theoretically all the pistons would look the same.

Yes. How do the pistons of a bank compare to each other?

The images above are all from a bank!

Here's another point about the terminology: If the filling flaps (which, actually, "swirl flaps" is a misnomer because the swirl channel is always open and doesn't have a flap), were always closed, then the engine tuning and the maximum speed, including the overall power output, would suffer, right? To the extent that you would notice it during kickdown.

Hufe wrote:

The images above are all from a bank!

Well, apart from "1. Zylinder, 20160817_175608.jpg," the pistons seem to be damaged in a fairly similar way. However, with that one cylinder, I'm less inclined to think it's due to "urine" from the injector, and more likely that some of the nozzle holes are blocked.

Hufe wrote:

If the bypass valves (which are actually misnamed as "swirl valves" because the swirl channel is always open and doesn't have a valve), were always closed, then the power output and maximum speed, including the overall performance, would suffer, wouldn't they?

In such a way that you would notice it during kickdown.
Yes, but you could also simply press the accelerator pedal harder. If the engine is making a terrible noise and emitting blue smoke, you should notice that, right?

I would suggest checking (or having checked) the injectors and the valves mentioned, as that should help determine the source of the overheating.

Here's another reason why excessive temperatures can occur in the cylinders of TDIs, even when the maximum fuel injection amount isn't unusually high: If there isn't enough air for the amount of fuel in the cylinder, the exhaust gas temperature initially increases up to a certain point. Therefore, it's not like in a gasoline engine, where a low lambda ratio can be used for internal engine cooling.
If you hadn't mentioned that the engine wasn't tuned, I would have suspected a typical problem caused by excessive fuel injection/injection duration, combined with inappropriate or no boost pressure increase. Unfortunately, the DPF doesn't show that the engine is smoking excessively, and many people have ruined their engines with such amateurish tuning.

Best regards, Rainer.

"These types of damages are common in the first series of 3.0 TDI engines."
Also, here's the translation:

"Also, seized pistons with a hole in the engine block."

The most common cause is faulty fuel injectors that no longer seal properly.

The 2.7 BPP engines are not affected by this. These engines have dampers in the intake system that reduce vibrations, thus protecting the needle valves.

There are no error messages beforehand.
For monitoring purposes, the MWB 72ff values (values from the zero-quantity calibration) can be monitored.
Strong negative values are a warning sign. However, I don't have the threshold values for each of the three measurements per cylinder memorized.

Okay, then the question arises, why simply continue driving until the very end?

Checking the injectors:
I'm sorry, but I cannot access external websites or specific files online. Therefore, I am unable to translate the text from the provided URL.

Best regards, Rainer.

Wauw, das beruhigt meine labilen Nerven enorm, dass der BPP nicht (direkt) betroffen ist. Thank you for that.
However, I completely agree with Rainer that one must, at least sometimes, be a more attentive driver and notice such things.
As I have since learned, the car with the aforementioned damage is owned by an older gentleman who primarily uses it for short trips.
It all somehow fits the picture.
I'm going to check the triggering times on my BPP tomorrow.
Until then, good night and thank you!

The same thing happened to an acquaintance of mine.
The car was still under warranty and was towed by Audi.
A new engine was installed, and the defective one was removed so quickly that he didn't even see it being taken away.

He hadn't noticed anything before, and certainly hadn't taken any measurements.

On the highway, there was a loud bang and a lot of smoke, which, like it has happened to some drivers before, brought the Formula 1 race to an early end.

Continuing the discussion here:

/viewtopic.php?t=28779

I would like to thank everyone involved, and I believe we can agree that the problem stems from a combination of "closed filling valves and defective injectors," with the injectors being the more significant issue.