I have put in three different thermostats in my 83 300sd trying to get the water temperature somewhere in the 85-90 range.
The thing that gets me is that it will run in the upper 90's whether the ambient temp is hot or cold and it appears that the faster I go the higher the temp gets. I also put in a new sender along with the thermostats and these changes did nothing. I am in Louisiana so I don't use the heater alot but I have recently. I have noticed that with the heater on, the water temp will stay right in the 85-90 range. I turn the heater off and the temp will rise back up. This tells me that it could be my radiator cannot handle the load, and with the additional water cooling of the heater coil, the system can regulate the temp where it should be.
I need some suggestions on what ya'll think.
Thanks,
Rodney