this morning when I left for work it was -13 outside so I let my truck warm up for 15 mins or so then took off. I drove the 5 miles or so to work and the coolant temp got up to 210 but i didnt have any heat to the cab. It also never cooled down from 210 once it reached that high. I am running an open grill, no winter-front or bra or anything. Has anybody else had a similar problem? Could it be the thermostats or something more serious? less serious? What do you guys think??