ATF in Crankcase

[crookednose]

Is it possible for ATF to get into the crankcase oil?

[Ali Al-Chalabi]

I don't think so. ATF can get into the coolant if the ATF-coolant heat exchanger in the radiator has a leak. Also, the coolant can get into the oil if you have a bad head gasket. But the only way for ATF to get in would be for it to first leak into the coolant and then leak from the coolant into the oil, and the likely hood of that happening is very small and the amount would probably be unnoticeable.

If you have a car with a vacuum modulator on an automatic transmission (I don't know your model specifically) and if it is a gas-burner rather than a diesel, and thus gets its vacuum signal from the engine manifold, and if the diaphragm in the vacuum modulator ruptures, it is possible for ATF to be drawn up into the engine manifold, then into the cylinders. At this point, it should be burned up or expelled into the exhaust (where it will ruin the catalytic convertor), but in some cars in some cases it has been known to flood the rings badly enough that it ran down the cylider walls into the oil sump. Of course, on SAABs and some other FWD cars on which the engine sump and transmission share a common casting, some other possibilities are more likely.

[crookednose]

Fimum Fit
Thanks for your reply. This must be the problem. I lost 2 1/2 quarts in less than a week without visible sign of leakage. Have fouled plugs on #1 and #2 cylinders but have not lost oil, in fact the oil level has risen.

[crookednose]

Bought a new vacuum modulator for less than $20 and the shop installed and adjusted it for no charge. The old one was completely shot, when you pressed the plunger it would shoot ATF about 10 feet. The tranny runs and shifts just like a new one. Just hope my engine can recover without having to do a valve job.