Kaboom!!

[Bigglezworth]

Yep. Confirmed why my one ride was down on power and feeling like it was a normal A6...... First clue was oily residue on the passenger MAF housing and air filter. Second was losing 1.5L of oil on the floor after removing the passenger side lower intercooler hose.... The final nail in the coffin was getting the turbo pulled off and confirming ZERO rotation on impeller wheel coupled with 4-5 pieces of debris that fell out of the header inlet. I have been unsuccessful in getting the turbine housing disconnected from the center housing as it's heat welded together. I have pounded and pounded to no avail. I wanted to see what was left of both the compressor and turbine blades, but think I will just be tossing the unit in the big round bin instead.

All of this speaks volumes to lack of performance. I know the drivers side was still boosting, but only using half the amount of air for twice the volume of combustion. Further, because the turbine/compressor is seized, that means there was significant back pressure on the passenger bank of cylinders that was likely increasing blow-by on the rings and increasing cranckcase pressure too. More crankcase pressure increases amount of oil laden fumes getting dumped in to intake stream where they were then condensing and uilding up in the bottom of the intercooler tract.

All in all, good to see that the damage was what I anticipated (for the most part), and that I can now concentrate on getting replacement parts sourced and installed. I would love to install a decent quality used turbo if anyone has one as this work is being done on the high mileage ride here.

PS For all those taking notes, both turbo's were replaced at 100K..... Car now has 245K and will have passenger turbo replaced in it's entirety and drivers side rebuilt. Compression on motor was still within 5% of spec just prio to undertaking this work. Doing other maintenance in the form of EGT's, upper O2's, Bufkin pipe (which was cracked and ready to fail), rollers - belt, stat, and pump were done 5K ago, full engine clean-up, CV boots, MAF clean-up, cam tensioner shoes, gaskets, SAI delete, new fluids, etc.)

[DHall1]

Better check the insides of the exh manifolds very close

[MaxRS6]

^+1 and a zillion

[Bigglezworth]

Better check the insides of the exh manifolds very close

Yep Doing a digital scoping tonight on all items downtrack of combustion chamber.

[ben916]

Is this the 10SecS4(Mark's) car?

[rwheelz]

Original bottom end/head gasket etc at 245k miles or has it had a rebuild?

[lswing]

Blargh, doesn't sound like fun. Didn't you just change cam adj shoes on this, anything get in there? If those are manifolds with 245k I can imagine something baking loose. Maybe get seized turbo rebuilt, just need the core/housing right? And any codes before this mess? At least it's winter!

[Bigglezworth]

Original bottom end/head gasket etc at 245k miles or has it had a rebuild?

Yes. Internals appear to be in fine working order. Compression doesn't lie.

Is this the 10SecS4(Mark's) car?

Yes. Bought with 208K 4 years ago and used as off season car up until this year when I bought a third and put the old summer beast in to winter action.

Blargh, doesn't sound like fun. Didn't you just change cam adj shoes on this, anything get in there? If those are manifolds with 245k I can imagine something baking loose. Maybe get seized turbo rebuilt, just need the core/housing right? And any codes before this mess? At least it's winter!

Haven't scoped things yet. Can't make any assumptions until I complete root cause efforts. Yes, this is the ride I was doing the tensioner shoes on (complete). I have MAF codes and some other codes which all speak well to the choke out and fouling occuring on the passenger bank. As for the turbo, I highly doubt it can be overhauled. I might just keep it and add it to the wall of 'fame' I have with other engine internals that have failed on various rides over the years. Have a nice mangled titanium connection rod, a folded over valve, shattered piston, etc. lol

[SteveKen]

Were you seeing any significant smoke out of the tailpipes prior to the loss of power?

[Bigglezworth]

Were you seeing any significant smoke out of the tailpipes prior to the loss of power?

Nope. I had some white smoke on start-up, but it was intermittent. There was NO dusting of headlights when accerating at all which is confirmed with good compression.

In looking at the 5 pieces of debris (longest piece is a nominal 15mm and radial in shape), it looks like the same material as the turbine wheel.... Internal damage would have had the engine rattling, lots of smoke, loss of oil pressure, etc., and engine wouldn't have kept running. A look inside each exhaust port shows normal carbon build-up on all 8 valves with no discernable damage. I can't visibly see anything looking in to the inlet and outlet of the header, but haven't scoped the primaries yet. Tomorrow. Got the turbine housing off and it looks fine. The turbine is heavily damaged and appears to be missing the outer portions of the flange which speaks to the debis (see stock photo for comparisson) The compressor housing looks fine also, although there is some wear on the compressor itself. I might be able to overhaul this bad boy with a rebuild kit and a replacement compressor/turbine assembly afterall.

[SteveKen]

I'd just pull the manifolds since you are this far into it.

Also, my question about the smoke was in reference to the turbos burning oil, not the cylinders.

I've got a set of manifolds if you need to source them.

[Bigglezworth]

I'd just pull the manifolds since you are this far into it.

Also, my question about the smoke was in reference to the turbos burning oil, not the cylinders.

I've got a set of manifolds if you need to source them.

I pulled the manifold yesterday when I removed the turbo yes. Will look inside the primaries with scope tomorrow to see if there is anything amok within. My monies on the debris coming from the outer edge of the turbine.

[Bigglezworth]

Final verdict is header is just fine. Thought you all might find it interesting to know that the shape of the primaries at the collector isn't round (like a plethora of aftermarket headers are), but rather pie shaped....

Debris is from outer perimeter of turbine. There was clearly some oil coking which lead to quick deterioration of the components. Clearly oil starvation. Also, with the turbine/shaft assembly worn away on the outer edge, it was able to move forward and backwards in the center housing enough that in turn saw the bearing/seal on the compressor end wear in to the compressor backplate. Large contributor to the large quantity of oil being dumped in to the passenger intake piping/intercooler.

I have sourced replacement parts and although I could look to do a rebuild with the improved 3 hole thrust bearing, new seals, a replacement turbine/shaft & compressor wheel, new backplate, etc., I am going to instead elect to purchase a complete CHRA cartridge. The delta in cost between a fully assembled unit and all the parts is negligible, and I would still want to acid dip the center housing anyway to ensure it's free and clear of any FOD which would actually make it a cost a bit more in total than just purchasing a replacement CHRA. Drivers side turbo was fine, but while I have the hulk out, the $40 for a rebuild kit is super cheap along with the hour of overhal labour. It doesn't need a new turbine/shaft or compressor, so I'm simply going to swap the seals and bearings out along with a detailed clean-up. Parts are 5 days to receipt, so barring any laziness coupled with various seasonal parties, I should have things reassembled, powerplant back in the body, final bodywork buttoned up, and fluids all replaced just in time for Santa to arrive! Sure wish the turbo's were located in a more easily accessible area which would have made this specific repair take a fraction of the time it will total in the end.

[DHall1]

Holy cokers Batman

[ttboost]

Yeah...that's ugly....

[Bigglezworth]

New goods!! Going to be a busy weekend getting everything back together. I've hit my usual January lazy mode, so don't know if I'm going to find enough motivation to get things all buttoned back up with a power effort over the weekend, but will be nice to get things reassembled.

[MaxRS6]

^Good luck and hope it all goes well!

[s8prtotype]

Wonder what some mild porting would do? Hmmm