Hello all, This is my first post and I had this issue with my D for a while. Its a 2002 Dodge Durango 4.7L. It started out a while back when the upper radiator hose came off because the plastic filler neck cracked and due to pressure the hose came off, I immediately stopped the car. I replaced the filler neck with a metal filler neck because plastic seems stupid in a cooling system. After fill and burping, noticed coolant wasn't ever flowing, got me thinking the thermostat was toast, it was, I tested the old one in water and didn't crack open till 207. I tested the new one and opened right at 195. Also during the repair I replaced the radiator since the fins were falling out and got a new radiator cap, did the fill and burp and I thought all was well. Then I took if for a trip weeks later after making sure it was properly bled, I noticed the temp gauge was high and stopped and opened then hood, realized the expansion tank was overfilled with coolant and leaking out. SO i refilled it(with burping) and had no overheating issues only when long trips of say 100 miles straight would it push a certain amount of coolant out into the expansion tank. Figuring that maybe the cap was defective, I replaced it with a different brand and it seemed to work, no more gurgling when starting up(way i knew coolant was missing from the engine). and everything ran great. Week later I went driving got stuck in city bumper to bumper during id say 80F day, the coolant temp gauge began to rise steadily. It then but never reached the last white line but never got cooler. No coolant being pushed out this time, so I decided next day to do some slow suburb driving then when at 1/2 mark, take it on the highway, all good no issues. went back to city speeds and coolant went up, got some speed, went back down, seemed all good. Then I hit a slow patch and coolant temp rose again. I decided to try out the ole turn the heater on full blast which seemed to help a little, but the weirdest thing that happened was that the heater-core got cold, no it was not set on AC nor defrost. The temp really didn't change then at a little less than 1/3 of gauge. Little while later the gauge hits 1/2 way and is still cold. Got it home and parked it opened hood with it on, whole entire engine bay was cold, aux fan was on and radiator was cold on the top. Any ideas? Much thanks!