It sounds like the turbo and head gasket could be separate failures that developed at the same time. Could the possibility that the car was recently over heated by the previous owner contribute to both occurrences?

Sorry, but I don't think that's very likely. You'd have to have damage to the water jacket, and the cooling system is closed. There would be less resistance to exhaust flowing out the exhaust system than into a closed, full system.

My car has a bad HG, and on startup makes a whuddududawhuddududawhudududa sound for the first 30 seconds it runs. That got worse over time. I'm doing an engine replacement. If you don't want to replace the engine, stop driving it, change the oil, and get ready for an HG job.

A bad HG can leak worse when cold than hot, as the metals will expand a little, and might slightly seal a leaky gasket after warming up.

Smell your coolant and see if it smells like exhaust. Mixed oil and coolant will have a distinct color and texture. Also, how are you checking for pressure buildup? I recommend starting the car with the radiator cap removed, then placing your hand in place of the cap and feeling for an increase in pressure.
White smoke is an indicator of burning coolant - but it's not the same as steam.

Good Luck sir
--
1990 740 Turbo, on its way to stock specs, maybe beyond

Hello,


You should establish if the compressor wheel is contacting the housing. Observe any scoring or resistance to rotation of the impeller. If this is indeed an issue, you should overhaul or replace the turbocharger and check for the symptom again.

Work one problem at a time, That is how I approach my exams. Sometimes you can skip over a hard problem and work an easy one, it may provide clues about the solution of the other.


Goatman