Q: Possible coolant in my oil but no oil in the coolant. Use about 1 l of coolant per 100km.

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It looks like coolant in the oil ; no oil in the coolant. Head gasket 100% and was tested via the radiator chemical test, leak down test in to the cyclinders, coolant pressure tests pass. The engine runs perfect. Slight white Goo in the oil cap.

My car has 135000 miles.
My car has an automatic transmission.

Check the transmission fluid. If all testing eliminates the head gasket, cracked cylinder head, etc, it may be a cracked radiator.Transmission fluid is sent forward to the radiator to be cooled. Ir runs into what is typically called the "side tanks" of the radiator. So the transmission fluid and coolant are both flowing through the radiator and kept apart just as the engine oil and coolant are kept apart in the engine by the head gasket, coolant and oil passages, etc. If the tank in the radiator is cracked internally, transmission fluid may actually be forced into the coolant as transmission fluid is under higher pressure than the coolant. Short of a cracked head gasket, cylinder head, or engine block, it’s really the only other source of any type of oil getting into the coolant unless the vehicle is equipped with an engine oil cooler as well.

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