Just bought a 99 4.0. Its overheating.
Here we go.
When it first overheated the coolant was boiling in the cooling system and coming out the reservoir. It was really a thick brown paste. Time for a flush. What I first did was drain the radiator (the coolant was very thick and brown). I then pulled the thermostat, which was completely broken into pieces under the housing. I replaced the housing with no thermostat and poured in a bottle of radiator flush and water. I let the car idle until 210 was reached and then I revved it up a down a few times. The needle remained in the middle. I turned it off and thought I had solved my problem (broken thermostat) and let it idle again about 5 hours later. After normal operating temp was reached. I then held the idle at about 3000 revs, until the needle moved slightly to the right of the 210. I immediately let go of the throttle and continued to let it idle, then all of a sudden the check gauges light flashed and the the needle jumped to the far right. I turned it off and checked under the hood and here we go again. Brown water shooting out of my reservoir (though thin this time). So today I ran water through cooling system initially with my garden hose. The water coming out was a healthy rust brown but eventually it began to clear up. I also installed a new thermostat and added more radiator flush to the water. I haven't tried to run it yet will be doing that tomorrow.
The original owner hasn't touched the cooling system and they bought it new. So everything is original which would explain why the thermostat was in pieces.
What could be wrong with cooling system? Should I continue to flush or assume its the radiator? Also is the electric fan for the A/C condenser or is it actually an engine cooling fan? If its a cooling fan then I've found my problem b/c that sob sat idly by while my I Jeep overheated.