Blown head gasket on '91 740 Turbo???

These engines are pretty sturdy, so although head gasket failures have occurred (mostly with serious overheating) they are not that common.

I have a thought about the dipstick tube, though. If the crankcase ventilation plugs up oil is forced out of the dipstick tube (at least in my '85) and I'm wondering if the tube extends not so far in your engine so crankcase vapors can be forced out the dipstick tube instead? If so, condensation could account for the glop you are seeing.

In any event, it is a good idea to check the ventilation. The system is really no more than a hose that runs from an oil/air separator box under the intake manifold to the turbo inlet duct, sometimes with a "Y" to the throttle body. The separator box is held down by two screws, but if you elect to remove it many people favor just buying a new one with the two O-rings it uses. You can do a confidence check by pulling the hose off the inlet duct and removing the oil filler cap. When you blow into the hose it should feel like you are blowing through a 3/8 inch hole instead of like a soda straw. (Now wipe that silly black ring off your mouth.) In my case, I never suspected the large ventilation hose could plug up, but given enough time it sure did.

Mike

That's exactly the issue my 740 Turbo had, and the reason it was only $500 instead of the $4K or so it would have otherwise been worth at the time.

In my case the only thing I could ever come up with is the O-ring on the dipstick was missing so moisture must have got down in there. I've put over 50K on it the last 6 years and the problem never came back.

Change the thermostat (and gasket) and check that the radiator hasn't developed a leak between coolant part and transmission cooler part. Check radiator by looking at transmission fluid via gearbox dipstick. If ATF is red and pleasant smelling radiator is usually okay.

A monthly "Italian Tune-up" is recommended if you do a lot of short journeys where the engine does not have the time to get up to it's running temperature.

All the best, Peter.

As winter comes on short trips cause moisture build up in the oil so a good warm run or the "Italian tune up "read rev it out hard, will rid the oil of moisture .I once ran a mini 998 through thick fog at low revs for hours in high cattle country at night ,my s-HELL oil was like milk the next day .This was extreme for sure but it shows what can happen .Congratulations you have a great car there use synthetic oil turn up the turbo and enjoy .We have two an 88 and a 90 .