The Mystery of Oil in Coolant Reservoir Solved Causes and Fixes

The black gunk in your overflow reservoir looks kinda like misshapen globs like what you see in a lava lamp, it may be engine oil. If you have oil in your reservoir you have a blown head gasket my friend. You can see it better in the reservoir then you can in the radiator. You have only 2 possibilities. The head gasket or the oil cooler/heat exchanger. It is not up to you to tell them what to do. They should diagnose the fault ... The problem, in general, is that there is a leak between the lubrication system and the cooling system. There are only few obvious where this can happen. The tech said he thinks it's the DSG transmission cooler since the oil in the coolant is very dark, vs the engine oil which is as clean as a whistle. I've only ever heard of oil in the coolant from a bad head gasket, or a cracked head. It's not impossible it's a cracked block, but I can't ... Sounds like either a head gasket (hopefully) or you might have a cracked in the block. Somehow oil that is traveling around the engine is getting into the ... Yes, oil can leak into the cooling system but that does not mean coolant will necessarily simultaneously leak into the oil. For example, if you ... The reason is that oil floats on the coolant, so it would tend to wind up at the top of the radiator, and whatever's on top in the radiator, ... When a head gasket fails, oil can leak into the cooling passages and then end up in the coolant. This results in the brown sludge that can be seen in the top of ...