I removed the thermostat (80C)from my 1985 300SD to see if it was stuck in the open position. My car will NOT get to 80C regardless of what I do (other than run it without coolant). The T-stat was not stuck open. I even put the T-stat in a pot of boiling water to see what it would do and sure enough it opened up. After removing it from the boiling water it closed up a few minutes later. My assumption is that the T-stat is okay.

I just recently purchased this car and I lack experience with this particular model's cooling system. The PO recently replaced the radiator and water pump as well as T-stat. I am attributing the lack of heat in the cabin to the low operating temperature, duh .

My question is though if the T-stat is okay then what other "gremlin" would cause a low temperature reading and poor heat output? It doesn't matter if I am driving fast or idling at a traffic light. The heat never gets HOT, HOT and the temp never gets above 60C (one time it may have gotten to 70C).

Also, what heat I do have is only on the passenger side. Anybody have a clue?

Kevin