Attention: TDR Forum Junkies 
FYI… My 2000 4x4 with 80k started to have some overheating issues. I never did boil over but it would get to the top of the “Normal” range when traveling at speeds greater then 75 or when towing the jeep. I first removed the radiator and cleaned the fins with simple green. I was astonished by how MUCH dirt, debris, and other muck was trapped in the fins. I reinstalled the radiator and went out for a test drive on a 95 degree day. It was better then before, but with the jeep, the temp would slowly climb back up to the top of normal.
I pulled the thermostat and placed it in pot of water on the stove. I slowly heated the water and monitored the temp with a thermometer. At 190F the thermostat valve open about 16th of an inch. It didn’t move again until 205F where it opened the valve to about an 8th of an inch. I purchased a new 180F thermostat from Cummins P#3954194 and placed it in the water. At 181F it started to open and at 187F it was fully opened where the gap was about ¾ of an inch. (As well as I could measure it). I installed it in the truck and no matter how fast, how hard, how much A/C, the truck just sits at 180F(level ground). It was well worth the $14 the thermostat cost.
I pulled the thermostat and placed it in pot of water on the stove. I slowly heated the water and monitored the temp with a thermometer. At 190F the thermostat valve open about 16th of an inch. It didn’t move again until 205F where it opened the valve to about an 8th of an inch. I purchased a new 180F thermostat from Cummins P#3954194 and placed it in the water. At 181F it started to open and at 187F it was fully opened where the gap was about ¾ of an inch. (As well as I could measure it). I installed it in the truck and no matter how fast, how hard, how much A/C, the truck just sits at 180F(level ground). It was well worth the $14 the thermostat cost.
