I've been trying to pinpoint exactly what's causing my 04 TJ to overheat as well and I'd like to point out something I didn't realize was a thing. Some of you may already be aware, but the OE coolant temp gauge does not give an accurate coolant temp reading the same way the oil pressure gauge does not give accurate oil pressure readings.
I figured this out by accident when my Jeep threw a code and I plugged in my code reader to check it out. Basically, if the needle in the temp gauge is even slightly above 210, your actual temps could range anywhere from 215-250 with the needle still on the "0" in 210.
In the pic, it's showing just above 210 what I expected to be 212-215, as a few others have reported, but I've seen temps on the scanner hit 250 with the needle in the exact same spot. Obviously that's no freaking bueno. The issue is exaggerated with the AC on and only delayed slightly with it off. Cranking the heater to max will eventually bring the temps down.
So far I've tried everything everyone else has: 2-core radiator - helped a bit but once temps hit 215 it was game over and it wouldn't cool down. I inspected the factory radiator, which looked good, and reinstalled it.
Flowcooler pump: mixed results but did not cure the problem. It's still installed, for now.
180 thermostat: before temps go over 215, temps will hold at 195-200 like they used to with the 195 tstat so no changes to report. It's still in there for now and will probably stay in there, I live in South Texas where there's no such thing as winter.
New radiator hoses: no changes but the old ones needed to go.
The fan clutch seems like it's good, it has what I believe is good resistance and doesn't spin a full turn by hand when the Jeep is cold, I haven't checked it hot. A new one is on the way along with a new radiator cap and overflow tank (the old one is pretty nasty).
I'm going to check the coolant level again after it cools down at work later today. I'm fairly confident I got all the air out when I reinstalled the factory radiator. I have a steep driveway and let it get to operating temp with a funnel full of coolant in the rad.
If the cap and clutch don't work, I'll replace the pump with a Mopar pump and get the radiator pressure tested, but honestly, it's starting to feel like there's no end in sight for this. I'm getting frustrated enough by it that I've kind of developed a case of "fk-it, give me a reason to V8/OM617 swap it", which sucks, because it's only got 83k on the clock.
I've been curious if my transmission isn't a part of the problem. It's got the 42RLE with a RubiCrawler and the tunnel gets
H O T. So hot that if I keep my garage door opener in the pocket by the coin holder, after 20 minutes of driving the door opener is so hot it won't work. On the bright side, my coffee never gets cold. I picked up a Derale trans cooler but, unfortunately, it's not going to work with my suspension. How much heat from the trans cooler do you think is soaking the radiator?
Luckily it's only been in the mid-high 90's the past few weeks but I'm still sick of driving around with the heater on and coolant temps in the 220's-230's.
Any suggestions are appreciated.