PeachParts Mercedes-Benz Forum - View Single Post - Coolant light on them off as engine temp changes ?

Diseasel300 · #2 10-17-2017, 08:51 PM

Coolant expands as it heats up. If you're marginal on the level in the expansion tank, it makes sense that the light would be on when cold, but go off as the engine heats and coolant expands and the level in the tank rises to raise the float. Fill the expansion tank and see if it still does it. Also find your coolant leak. It may be related to the next point...

Poor heat at idle that increases when the engine is revved or the vehicle is under way can point to a failed/seized auxiliary coolant pump located near the monovalve (or duo valve on some cars). Its sole purpose is to circulate coolant through the heater core to improve heating at idle and low speeds. You may find your shaft seal failed on the pump which can also be your source of coolant leak (Just went through that myself).