As I explained in a previous post, I recently found a light tan gooey substance splattered inside the radiator overflow tank of my 1980 245. I asked the forum what this could be, and most suggested that it was oil, and that there was a possible break in my head gasket, however one person suggested that if I had an automatic transmission, it could be oil from that instead leaking into the cooling system. I recently took the car to a mechanic who confirmed that it was oil, but not much beyond that. My question is where the oil came from, as I do not want it to be a head gasket. A few months ago, I replaced my automatic transmission with a M46, and during that process, unscrewed the two oil circulation lines that go from the automatic transmission to the radiator. Those holes now sit unused, but I'm sure residual oil still is sitting inside the radiator. Could my changeout now somehow be causing this oil from the transmission system to leak in the cooling system, or is that crazy? How could I test to see if it was from the engine oil, or from the transmission system? Thanks!