Over cooling type issues w/ 1979 300d non turbo

[tdoublenastywitit]

My 300d has a lot of trouble warming up all the way as of late. It had been sitting for about 2 months but now I'm driving it again and temps are in the high 30s outside.

It takes about 10 mins to even reach the first notch on the temp gauge. I think that notch supposed to be 60°C. And it really doesn't get much better than that, it never reaches the 80° mark and usually just hovers in between the first notch and the 80° notch, so somewhere around 70°

All my other om617 sit at about 85 - 90 degrees.

Is the cold weather doing something weird to my coolant? Previous owner could have put too much water in it, I dunno if that would do anything.

My thermostat stuck open?? I just feel like it should reach full op temp even if it was stuck open , just take a lot longer, but it never does.