I have a 05 3.9l Sport and I had a overheating issue about 5 months ago. I replaced the thermostat, housing and most of the plastic parts. The system is properly blead and leak free. Now when the car is driven the fan comes on and runs at high all of the time. The temp gauge doesn't move at all, but the fan stays on high all of the time. If I turn the heat on, usually for less than 2 min, the fan goes off and then operates normally. I am completely stumped and any help would be appreciated.