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I did a headgasket job on my 940 turbo early in May, since there was a LOT of oil in the coolant, accumulated over probably a year or more. It's been running much better ever since, except I'm still noticing oil in the coolant tank at the high water mark. At first I assumed this was just some of the leftover oil from the leak working its way out, since I didn't do much flushing. But it recently seems to be accumulating again, and there is a slight slick on the surface of the antifreeze. Nothing like before, but still troublesome. The radiator is only a couple of years old, and the transmission fluid seems healthy, so I doubt it's the transmission oil cooler. I've done headgaskets before, and always by the book, this one included - never any problems. So unless the gasket I just put in was defective (Reinz), I'm wondering if the turbo oil cooler might be the culprit. I've never seen any posts about one leaking, but I figured I'd ask to see if anyone has had a similar experience.
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Did you check the head for warpage, or have it skimmed?
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Thanks, guys for all the input. Head was not warped, and quite clean, so I just cleaned it up even further and threw the gasket on. I've done this before, no problems. But maybe this one's the exception. I'll keep tabs on it and report back. If I have to go in and re-do the gasket, it shouldn't be that hard - I used anti-seize on the exhaust studs, and new head bolts, etc...
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After my son replaced the head gasket in his 1995 944T, we had a similar problem with oil in the coolant reservoir. Replacing the oil cooler did not fix the problem. The problem persisted for several months, and then got worse, but there was no coolant in the oil.
I again replaced the head gasket (the one my son installed) about ten months ago, and there has been no oil in the coolant since. Not liking to do anything twice, I used the best head gasket I know of, a Cometic head gasket. Expensive at $105, but worth it to me if it cured the problem.
I used dishwasher detergent to clean the cooling system. We did about six cycles of driving for a few days, doing a complete flush with fresh water, and adding dish washer detergent again. Dish washer detergent doesn't foam, and works well in the cooling system.
When the engine is running, lowest oil pressure a car runs is greater than the highest pressure in the cooling system, that is why you probably aren't getting coolant in the oil. Although when the car sits, after being shut off, there is pressure in the cooling system and none in the oil system. A small leak is probably not letting coolant into the oil, yet.
My experience says you need to do the head gasket again.
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john
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it's possible the cooler has split. seen in vws but not volvos. i would pull all the hoses and the cooler, clean everything, reassemble and run water and shout or dawn to get rid of any residue. done it before, works good after a gasket failure. porsche has a bulletin detailing the operation, that's where i heard about it. good luck, chuck.
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Turbo oil cooler?
A turbo oil cooler, as I understand, and am not entirely sure, is a self standing assembly usually mounted to the side of the radiator on Volvos. Volvo would not rick mixing engine oil and coolant in that was so I understand.
If your awesome Volvo 940 is an automatic, the automatic transmission uses what should be an isolated chamber in the engine coolant radiator to cool the transmission fluid.
Is your turbo a water cooled turbo in a 1993 940? A turbo or super charger coolant jacket, if water cooled, is an entirely isolated chamber from the lubricating oil and moving works. The water cooled turbo or super charger may normally use the same coolant the engine does, yet on very high end and racing autos, a different configuration may be used to reduce risk of mixing fluids.
If you did not flush the entire water jacket spaces and pieces of engine oil using a solvent cleaner detergent including:
- rubber hoses (you did replace these, yes?) including the under dash rubber heater coolant hoses
- the heater core under the dash
- the radiator itself
Oil may remain in the water jacket spaces and is migrating up to the highest level over time - the coolant reservoir.
Oil will continue to collect until it has worked itself out. So, you'll collect for oily scum and slicks in the coolant.
All coolant rubber hoses are deteriorated when exposed to hydrocarbon compounds like engine oil. Even if you have silicon coolant hoses throughout, the rubber, or much more slowly, silicon material deteriorates as well as any coolant system seals like at the water pump.
If the oil accumulation rate at the coolant reservoir tank is steady, I'll guess the oil migrating, when the coolant is hot, to the highest level of the coolant system.
If all of the sudden oil, or periodically, massive oily amounts accumulate in the coolant reservoir, you may have a cylinder head gasket fault. A fault in the gasket, or assembly. The cylinder head was not properly machined, compromising the chance of successful cylinder head gasket seal.
Again, you may want to consider flushing the coolant system with a mild solvent detergent in hot water. This is a really messy task and not so environmentally friendly.
Before doing that, perform the check to unequivocally discern a faulty cylinder head gasket. You could also have a fracture between chamber in the cylinder head, albeit far less likely as coolant and oil (much higher pressure) are both under pressure.
Questions and comments?
Well wishes?
Thoughtful thoughts?
Peanut butter and hunny sandwich and a fresh ice cold glass of buttermilk?
Garlic Powder Guy
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Garlic KICKS ASS!!!!!!!
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Volvo started using the oil to engine coolant style of oil cooler with the 1992 model 740/940 turbos. I have not seen one fail, but it is possible.
The turbos have been water (engine coolant) cooled since the 1987 model year.
There are no coolant hoses under the dash in a 740/940.
I use dishwasher detergent to clean an oil fouled cooling system. I drain the antifreeze coolant, add fresh water and at least one pellet of Cascade dishwasher detergent. The car is driven for several days, and I catch the coolant as I drain it, and repeat the cycle. I can take a lot of flushing.
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john
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