Jeep Repair: 99 XJ 4.0 runs hot, Christian Customs overheating jeep xj

Question
Like the subject says, I have a 99 XJ, 4.0, A/T, 190,000 miles, etc. My problem is that while towing or in slow traffic, the temp really starts to come up(215-220). The electric fan kicks in but the mechanical fan never does. Over the past 3 years, I have replaced the fan clutch 3 times, still not working. I've done some research and found that that thermal fan clutch needs a surface temp. of about  180-190 degrees in order for the valve in the clutch to open and engage the fan. I've checked the temp of the clutch with an infrared thermometer many times and the highest temp I have seen is about 148 degrees, even with the engine running at about 215. I am starting to think that my problem is my radiator, and it's inability to transfer enough heat away from itself. It's an aftermarket 2-row radiator with the "standard efficiency" core...meaning approx. 10 fins per inch, and it is completely clean. The original radiator was a 2-row but it had the "high-efficiency" core with approx. 20+ fins per inch. Could this be the reason why I am not transferring enough heat out of the radiator? I had zero problems with overheating until about the time I replaced the radiator 2 years ago. Or could it be a water flow issue? Collapsed hose? Corroded t-stat housing? Im running out of ideas and Im not going to throw anymore parts at it until I get another opinion. Thanks for your help!

Answer
Well dont get to upset over this yet it could be a simple problem. Most Xj's are happy at about 210 under normal use. Why this is i dont think anyone really knows but its just a fact, 210 is where they are happy. Now more times then i can tell ya you are going to see them creap up there to about 215 or so. A little bit is ok, like if it is at 210 and you turn the motor off and after about 5 min you turn it back on and it s at 215-220. that is normal. What would not be good is if once you are back out on the road and running that it would not go back down.

3 things i want you to check on your jeep. First check the line coming from the top of the radiatior to the overflow tank. Take this line off and make sure that it is clean and clear. this tube is the number one reason from jeeps cherokees to blow out a radiator. 2) go to the auto parts store and buy a head gasket leak tester. ($20) and test if your head gasket is gone. and 3) buy a flush kit and really clean it out. this could solve your problems.

Now about your fan not working, are you saying that it is not turning at all? or you just dont think that it is doing the job that it needs to be doing. Do a small test. Run your jeep under normal usage and after it has been up to temp for about 10 min or so stop and put the jeep in "park" and rev the motor one really quick time. and see if you can hear the fan cut in and out after a second. it will be a short delay after you rev the motor but you should hear it.

Hope this helps.