KKK KP39A catastrophic turbine failure

[Greasecar]

Anyone seen something like this before?  Just picked up a PD engine out of 2004 Jetta which had a severe turbo failure.:

 

I am having a hard time imagining how this could have happened.  The shaft bearings did not look to be worn and there was no evidence of foreign objects or external damage.  The turbine shaft was of course severed and the resulting turbine shrapnel was blown into the intake resulting in heavy pitting in the #2 piston face (only one I have been able to observe with my borascope so far) and took out the rings of at least one piston.  I hope to get the head off for more detailed internal inspection later today.

Here is the compressor turbine:



And from the back as the compressor scroll was removed:



Has anyone seen this kind of failure before?  I have seen several posts on TDI club in the past with similar damage (though not as extreme) but no one was able to determine the cause.

My theories are:

-Failure of VNT actuator resulting in runaway leading to some form of wobble or warping which caused the turbine to hit the scroll.
-Failure of a bearing with a similar result
-Something coming loose in the intake system hitting the turbine (no way to investigate this without the car)

[A2TD]

Looks like a victim of surge to me...

[subsonic]

Man!!  I would have liked to listen to that thing when it came apart!

SSSCCCRRREEEEECHH!!!!  KA-Booom!

[TDSii]

RIP...  :shock:

[Greasecar]

Here's what I found when I pulled the head.  Yep, glowplug snapped off and busted up one of the cylinders.  The question is; which came first the GP or the turbo?

[Slave2School]

PDs have very fragile GP's so perhaps one was installed after being dropped, busted a chunk off, bounced around a bit in the cylinder and then exited through the turbine section, causing an extreme out of balance situation, snapping the shaft.

[Greasecar]

I have the same theory in regard to the turbine though I wish there was some obvious evidence of impact to support it.  The exhaust turbine is less delicate and better secured to the shaft in comparisson to the compressor turbine so it is not un thinkable that a minor collision on the exhaust side could equate to catastrophic damage at the other end of the shaft.

Anyone know of any good turbo rebuild shops?  I also need to decide if it is worth rebuilding this engine, the only damage to the cylinderhead is the pitting you can see around the valves (and on the face of one) but I don't think I would feel comfortable re-using it.  I did find someone selling a set of pistons and a head from a block which was fractured at the motor mount but I'd still be looking at spending over $1000.