There's a lot of soot buildup on the inside of that intake. Maybe that's what caught fire. Is there any more soot buildup anywhere else that you can see?

 

It's a TDI (with EGR)... the carbon buildup is normal and ofcourse it will be throughout the whole intake system....
Everything like the intake horn shown, the intake flap downstream of it, the intake manifold, and the intake ports & valves will have carbon buildup.

 

It's a TDI (with EGR)... the carbon buildup is normal and ofcourse it will be throughout the whole intake system....
Everything like the intake horn shown, the intake flap downstream of it, the intake manifold, and the intake ports & valves will have carbon buildup.

If this is written in response to me just wanted to say I know it's a TDI and I know that soot accumulates in them. It seemed like, from pic #3, that there was a decent amount in the intake and I figured there might be even more elsewhere possibly causing the problem.

 

Some how something hot enough to ignite the normal oil and carbon in the intake got into the manifold.

Potential candidates I can think of are:

1. Hot exhaust gases due to a fuaulty EGR cooler system
2. Hot metal from the turbo
3. Faulty inlet valve allowing hot combustion gases back into the inlet

Since also reported a engine running faster in an uncontrolled fashion that suggest 2. and a turbo failure letting lots of oil into the inlet and the turbo rotor hitting the casing creating the hot metal in the inlet to ignite it.

just guessing but i would be looking at the turbo next

 

I will be looking at turbo for sure. The soot levels were not bad.

 

Yep, something doesn't add up, something else failed

 

My big diesel mechanic said he saw this on a ford 6.4 where a valve stuck open and let the fire out. I looked again and no oil came from turbo as the charge pipes were clean. My friend said it ran slightly rough as he passed a truck under harder acceleration right before losing power. I'll let the guru chime in later this afternoon. I'm sure it will cause lots of curiosity. Feeling a bit bad for recommending the purchase to my neighbor.

 

Let me guess.... it's also "tuned" ?

 

Bone stock

 

Maybe it should be tuned.

 

Pull your lower intake pipes off and check for engine oil pooling at the bottom of intercoolers. It will usually pool in the pipe closest to the turbo where after the Y.

Your anti shudder valve should close off on key off and prevent run away...

There are only a few things that will allow your engine to run away. Usually it is turbo seals hatched allowing engine oil into the intake.

First check anyways...

 

All of this, plus intake ports and valves, will be effected by said buildup
The valve on the lower left is the "cleanest" part of everything.

 

My guess would be engine oil fuel dilution got to the extent that vapor condensed and pooled in the inlet tract and then heat from the EGR system caused it to auto-ignite.

Get an oil analysis done and replace the inlet pipe and clean the rest of the whole intake is my advice.

 

Agreed! Thank you for taking the time to give this some thought. My friend heard from the mechanic and he decided to have it towed in Monday. The shop said there may be an issue with the glowplug harness being involved although I'm not sure how. The middle glow plug passenger side was separated at the middle of the housing when I took the intake off. Intakes are big $$ so I considered plastic welding the one hole on the intake and replacing the inlet pipe.

 

Wait... what?

So the GP harness shorted out on the outside of plastic manifold and caused a spark inside the manifold to ignite the carbon deposits on the inside?

 

Yeah no way that happened. I'm waiting to hear back from the owner and lead mechanic as he will have some answers. I still don't see how oily soot can spontaneously combust. There is soot in the intake of every VW TDI with an EGR. The engine ran well and pulled as it should prior. I just see the valves being an issue which sends me back to puzzled.

 

Car is back from the shop and a stuck open EGR valve was the culprit. Said it wasn’t a fire situation but extremely high heat that finally melted through the plastic intake parts causing several holes. Car has 108k miles and recommend EGR replacement before it becomes an EGR and Intake Manifold replacement which is double the price!

 

No 1 on my list in the 4th post