Just bought a 91 mighty max, and was running some strong heat. Went through it and changed all the fluids. The radiator is brand new, and was quite dry. Now that I went through it. Not much heat, and engine is running cool. Good for the engine, but uncomfortable with all the brutal cold we have had in New England so of late. Do I now dig into the thermostat and change it? I was wondering where is it, and are there different ones that open later for a warmer running engine, and better cab temperature? Any help will be appreciated. Thank you Gs.