I just purchased a 91 300SEL. I knew there was an oil leak that looked like it was coming from a valve cover gasket. When I got the car home I began to run over the systems looking at how Mercedes puts things together and so on. Well the first thing I was looking at was the dark brown color of the coolant over flow tank. It did not look right. I opened it up and stuck my finger in (yes engine was off and cold) pulled it out and it was covered in thick black sludgy oil. I removed the over flow tank to drain it and get a good look at the fluid. It was for sure oil. About 1/5 of the tank volume was oil. I then took the upper radiator hose loose and it was very new and green, not what I expected.
Is it possible the person I bought it from flushed the system knowing it had a head gasket problem but forgot to flush the over flow tank? No matter either way I paid very little for the car with an understanding it had 250,000 miles and a very bad oil leak. Any out come is on me. I am just trying to evaluate what damage may be done.
So you know I am very very automotive savvy. I have been building Ford 351W engines for my 69 cougars for many years. I am applying that knowledge to the new Mercedes but want to be sure there are no other special engineering things I need to consider before I start tearing down the upper end of the engine or just go for the full rebuild.
Thank you much for any input. I am so excited by this new car.