Raj Morar

Will appreciate any assistance. Replaced the head gaskets on my E320 auto. Went on a very short ride, heard a whining sound then no gear. After turning off the engine for a few minutes, the drive is ok, for a few minutes only. There is a small black PAD pump that is running all the time, which did not happen before. Will this cause it. It feels like the gearbox oil is not cooling, although the radiator is only 5 months old. Many thanks