Sorry for yet another overheating question. I've searched, this forum and other for help with no avail. So as kind of a last ditch effort Im calling on other modified XJ owners to help me out.
I got a 1999 XJ 5.5 long arm lift on 35's with Dynatrac Pro Rock 44 front and 8.8 rear both locked with 4.88's. 1 ton steering, WJ brake swap. PSC Hydro assist Also have a JCR offroad winch bumper and big winch, rear fender armor and so on. So its got some weight to it.
After my radiator literally exploded, I started the process of replacing everything in the cooling system. Including replacing the head gasket. I had the head rebuilt and faced flat. Then I went and replaced just about everything.
New (rebuilt) head
New Head gasket
New Champion aluminum radiator
New water pump
New Thermostat, (tried a few)
New Temp sensor
New clutch fan
New fan shroud
New hoses.
Rod louvers Hood vents
Burped it many times.
Electric fan is working (and kicks on at 220)
New plugs and wires (not cooling but putting it out there)

I live in Phoenix AZ. It's like 90-100 degrees outside give or take right now My Coolant temps are climbing into the 220's then 230's and on up into the 240-250 range.
the temp only climbs when im driving. Doesn't matter if im around town or on highway. The jeep could run in my driveway and not overheat. Temps just creep on with the AC on or off, faster with the AC on.
Anyone who has any suggestions I'd love to hear them. Im at witts end with this and it is consuming so much time

 

Two thoughts. Since you have a 99, have you checked to see if you have the head that is known for cracking? Just thinking. Also, I have a similar bumper / winch setup and I am looking at relocating the winch and cleaning up the bumper. Just too much blocking airflow from the radiator when driving.

 

Yeah it's not that head. I had the machine shop magnaflux the head before it was completely rebuilt. Machinist was very much aware of the cracked jeep head problem. There is a possibility that there is some blockage effect on the radiator. It really doesnt seem like much though. However its one thing I have not done.

 

You mite check the A/C condenser to make sure it fins are clean and not plugged blocking air flow .

 

I live in the Az desert also and here's what I found out. We live in a unique climate that auto engineers don't take into account when they design these things. So some vehicles are just going to run hot in places like Phoenix especially in stop and go traffic even if everything is up to par. A couple things you could do is replace the OEM fan clutch with a Grand Cherokee clutch, it has been pointed out here that they will pull more air than the Cherokee clutch. I ended up running a switched override circuit to my electric fan relay so that I can make it run constantly when in these conditions and it helped immensely.