Okay, my coolant is not rated low enough for the weather we are getting tonight, and I cannot get it to cycle through the engine...... I had the engine at the red zone twice already, and that amount of heat STILL won't get it to cycle through the system. It was running perfectly about one hour ago, and now it won't cycle, what could this be?????????? thermostat? If so, should i pull it, and run the truck without it the thermostat? I only need to cycle, and mix up the coolant with some fresh antifreeze. I am NOT driving it anywhere.