With the warm weather the last few days, my '88 Sammy has been running hot(just short of the H-zone on the guage). Today I replaced the 195(!) degree t-stat that the previous owner installed with an OE 180 degree unit. It helped some, but it still seems to be running hotter than "normal." It will probably be ok for street driving, but I am worried that during off-roading it may overheat. Anyway, I found a 160 degree thermostat for sale, and am thinking about installing it, but am wondering how it will effect winter driving. I live in Northern Colorado, where it can be 110 degrees in the summer and around 0 in the winter. Has anyone used a t-stat with this low of a temp?

I used a 180 in northern utah, I would do some more trouble shooting,what ever you have 160 or 180,dont think it will help much.

Is your radiator dirty? Sure that you have checked but if not spray a hose through the parts you can get at from the back side, flush your cooling system or have a radiator shop do it for you. Check for proper operation of the clutch fan. Hope these tips can help you out. 

Ok, so I think I may have found my problem.
I drove it around this afternoon until it got nice and hot, then parked it and popped the hood. I found that my fan was still spinning freely, hardley any fan clutch drag. So, I don't think the thermal clutch is locking up the fan like it should. I JB-Welded the clutch solid just now and am hoping that helps. I know it may cause a slight drop in mpg, but it will work for now until I can get a new one.

Thanks for the help guys!