Tracing the Source Oil in Coolant Reservoir and Its Implications

The oil always ends up in the overflow. It floats on the coolant, so it's the first to get pushed out into the expansion tank when the motor warms up. A leak between the oil containing part of the block and the cooling part is the only way that you can get motor oil in the coolant. The car runs and idles great, their are no leaks in antifreeze or oil (on the ground), no overheating problems, and starts up fine everytime. One tip, is to double check the oil cooler itself for trueness against a straight edge just to be sure that it is not slightly warped. Not ... There is potential that your oil and coolant are mixing due to a broken head gasket or a cracked cylinder head. Open up the radiator cap and ... If you have oil mixed with coolant in the reservoir, you will notice a thick, milky or gravy-like substance that is a tell-tale sign that you have this issue. Typically it's an oil cooler failure. If the cooler wasn't properly torqued last time, it could have lead to the premature failure this go ... A blown head gasket allowing oil into the coolant would also allow coolant into the oil, causing a frothy or milky look. I inspected my engine to find watery oil on the outside of the air intake and abs brake module (behind the coolant reservoir). A quick check of ... I have a 09 Beetle, my mechanic called me with my issue and it was a failed oil cooler. I had oil in the coolant and the car overheated.