Audi 3.0 TDI Engine Failure: Causes & Symptoms

Hello,

As can be seen in the picture, the pistons are from cylinders 4 through 6.
suffered greatly, and you can see the melting damage.
The injectors and almost all of the exhaust valves are burned.

Cylinders 1-3 are not affected.

What could be the reason that only this cylinder bank is affected? All the injectors are still original and from the first production run. (AB)

Is it possible to upload a picture from a smartphone?
If not, I will upload them later, if necessary.

Quote:

Is it possible to upload a picture from a smartphone?

Yes, use the "Select file+" button.

Swirl flaps

Please explain the throttle valves to me.

Perhaps one cylinder bank received insufficient combustion air, which caused it to overheat.

There is one swirl flap unit per cylinder bank. The servomotors use plastic gears that will eventually suffer from tooth breakage.
If the servomotor's position monitoring system fails to detect the correct position, the swirl flaps will remain closed even under high load, and the affected cylinders will not receive enough air (because the intake channel is not open).

Due to the lack of air, the combustion process gets closer to the piston material, and the exhaust gas temperature also increases significantly. Since "healthy" exhaust gases come from the other cylinder bank, and older EU4 engines were not subject to such strict monitoring, an error is usually not displayed until half of the engine is completely damaged.

EDIT: There is a lookup table (map) for the swirl flap position. Those who want to prevent this problem from occurring in the first place can have a competent chip tuner "adjust" this map, so that the frequency of adjustment and thus the risk of failure is reduced.

That must be the exact problem, as the exhaust temperatures were so high that the cables in the area of the catalytic converter had melted together, including the connector for the crankshaft position sensor; it was just a clump of melted material.

Thank you very much!

Now I can finally go back to sleep.

Of course, this also means that the DPF (Diesel Particulate Filter) was likely regenerated more frequently, because somewhere the soot that is produced in greater quantities due to the lack of air has to go... and that also contributes to high exhaust temperatures.

The 2.7/3.0 TDI engines already have air-gap insulated (double-walled) exhaust manifolds. So, it shouldn't get *that* hot around there... or is the melted connector located at the back, near where the (single-walled) exhaust pipes lead to the turbocharger?

Absolutely. The connector is attached to the transmission bell housing. The catalytic converter and the exhaust pipe are located in this area. Even the catalytic converter shows significant signs of corrosion.

Thank you again.

Can you upload the pictures, please?

Here are some pictures.

Thank you for the pictures!

It seems like you were lucky, and the cylinder walls are undamaged.
A little bit of tinkering, new pistons installed, and it works again .