So my 01 LB7 keeps getting hot. I was driving home from work yesterday and the water temp kept goin up. I turned the heat on and blew hot air for a few seconds than was just cold air. Seemed like that made matters worse cuz the temp rose more after that. The truck did not overheat and has new headgaskets, new water pump and new thermostats. I tested the thermostats and they are good. Any ideas??! Bad heater core or radiator??? If I don't use the heat the temp stays cooler but not where she has been all winter long.