It sounds to me like you might have a blown head gasket. It won't always manifest by pushing coolant into the oil.
If it is a blown head gasket, there would be a constant bubbling out of the tube in the overflow bottle. it could be fast or slow, it just depends on how big of a leak there is in the head gasket. Something is pushing coolant out of your radiator into the overflow tank. This means a force is getting into the coolant system and displacing the coolant in the radiator. that requires something with a pressure greater than that of the coolant system that can interface with the coolant system if a failure occurs.
What to do? Tests! Always have tests done before a repair to verify. I would get a compression test done to make sure you aren't losing compression into the coolant. You can rent a compression test from most US part houses (example; O'Reilly Auto parts). Some places may even help you test your vehicle in the parking lot.
There is also this article on head gasket tests.
https://www.2carpros.com/articles/head-gasket-blown-test
Let us know what you find! Good luck!
Jan 22, 2019 at 4:52 PM
