A4 2.5 TDI Quattro B6 Turbo Failure

[Guy]

The turbo failed dramatically, the compressor drive shaft severed causing the compressor to chew itself and sucked the full contents of the engine oil into the intake duct. The engine ingested oil and although ran lumpy for a while after cooling down seized with cylinder hydraulic lock. I removed the injectors and cranked the engine on the starter with explosive ejection of oil - anyone doing this make sure you place more than large rags to catch the oil - BP has nothing on the fallout I caused. I isolated the oil supply to the turbo, loosely reassembled the engine to run without intake connected just open head intakes and hey its running smoothly. So I figure I may not have bent con rods and bottom end damage. The turbine spins noisily no surprise as its not connected to its compressor. So thats the story so far, have new turbo from Garrett, has anyone had similar experience and can give me some pointers on what else I should be checking for before I fit the new turbo. The breather system I guess is an obvious one along with complete cleaning of the intake system, oh joy.

[Alan02]

Yeah, make sure you get the Intercooler cleaned out professionaly. Radiator repair companies can uaually do this.

[Alan02]

Oh ! and you may need a new Exhaust system. May have filled Silencers with oil.

[Guy]

Many thanks Alan

I managed to clean both inter-coolers with strong surface degreaser and hours of flushing and aqua vac treatment, the exhausts, well replacing them is not a financial option, that in combination with known damage and that of other potential issues would finish the car.

Its all back together now and its running well aside from diesel knock pulling away and smoky cold starts. I figure that the injectors suffered from the oil ingestion. These are expensive items, the pin movement sensor equipped injector I had previously replaced but guess that to will be damaged. The best options so far seem to be overhauling them at £70 each.

I also believe I found the causal factor to the failure, turbo overspeed due stuck VIGVs. These were contaminated with carbon deposits, I guess poor breathing.

I had suffered from what had appeared intermittent turbo boost, this would be explained by sticking VIGVs. Stuck in the minimum position the compressor would not be working hard so trying to extract much power from the engine the turbo would be free to rotate much faster than normal. In my case the failure occurred after a quick excursion.

Has anyone got any good steers on diesel knock, I sadly lack experience of such spending most of my time on petrol engines.

I hope my experience and findings are of help in particular to the importance of engine breather system and preventative turbo failure measures. I would now be looking to replace the turbo at cam belt change intervals. It should not like the cam belt be treated as an on condition item only to be replace on failure, the repair costs could finish the car.