No I have not yet, it heats up to regular engine temperature (210ish) and maybe a little over pretty fast just sitting on idle so I kind of figured it's not the light bar. I just noticed this today as well. I will take it off and drive with it off just to make sure. As of right now though, I just drained the whole system again and I'm going to flush it again. Last time I removed the thermostat and the lower radiator hose and pushed water through the thermostat housing with the water hose. What's the best method for flushing?

 

"What's the best method for flushing?"

When you remove the radiator cap (on a cold engine please) does it look like:
A

or
B


?

 

Clean green.... So "A." Lol

 

I'm guessing if it looks like "A" I don't need a flush...?

 

Yep, it would just be a waste of time & resources.

 

Wait a hot minute. Where is it spitting out coolant? Did you use a brand new good brand radiator cap? What is the lbs on the cap? What brand and temp rating thermostat did you use? How much coolant is in your overflow bottle?

 

...and the reason it gets up to temp, without overheating, is because your fan clutch is operating properly. It's doing it's job, managing temp at idle, or slow crawl. Highway driving is a different story, you need flow to cool. If air isn't flowing, you'll overheat.

Remove the lightbar and winch. It's free. Drive. Document. Report back.
^THIS
Read his post. He removed the rad cap. Of course it's going to overflow, LOL

 

No I am asking if it is spitting coolant with the cap on. A weak cap or incorrect cap can cause these issues. Very similar situation with my SRT4. When i would run any boost the temp would rise. Only change was to a factory cap. If the OP confirms it is a new cap then let's move on.

 

Fan clutch does come into play even at cruising speeds. Spin it by hand when at operating temp. Engine off of course. Stiff or loose.

 

Loose, as it should be. Cruising and idle is not enough load to get the xj mechanical fan to fully lock. Take an xj up a mountain ascent, it will shock you how loud it is when fully locked.

 

Fan should be hard to spin when at operating temp not easy. Got nothing to do with rpm. Had similar prob years ago changed clutch solved it. Also a three core rad will run warmer than a two. I guess because of the length and height
of xj rads normal rules dont apply.