I had exact same problem. Mine would slowly creep past 210 while on road and max out about 220. Offroad was terrible, it would be on the verge of the red line just a few minutes after slow driving in 4-low.

My husband installed a high volume FlowKooler water pump. Now my temps stay right around 195 on or off road. Under high demand off road it sometimes gets close to the 200* mark.

He also installed a manual switch (a few months ago) for the aux fan which I haven't had to use since the new pump.

Everything else on the cooling system is stock with a 195* t-stat.

The water pump is a little pricey, but it definately worked.

http://www.summitracing.com/parts/BRA-1747/

 

You can squeeze the upper house to get the air out as well if you don't want to change anything. Squeeze it while its running, sometimes it might take a couple attempts of squeezing it then driving it a bit.

 

http://www.lunghd.com/Tech_Articles/...BurpAirMod.htm

 

My 89 Laredo would spew coolant out of the reservoir after turning the ignition off. I was scared I was going to have to buy a new radiator b/c it was overheating as well. Turns out it was just the $5 Thermostat. I bought a 180F instead of the stock 195F, it gets pretty hot during California summers. After flushing and installing my new thermostat, it never gets hotter than 1/4 of the meter. Try replacing the thermostat first before anything else, even if it's not the underlying problem, it only cost me $5.

 

How hard was it to replace the t-stat. I am considering a 180f because I drive so much stop and go. I creep up over 210 as well but the fan kicks on like it should and cools it back down.

 

It was super ez, just have to remove 2 bolts (1/2") in front of rocker arm cover, and clean the thermostat housing. Just make sure u buy the $1.50 gasket as well along with a small tube of gasket SEALANT, (not the gasket MAKER) ($3). Oh and make sure to follow directions on the sealant to a "T". (just let it sit for and hour on just finger tight, then tighten the rest of the way, 15ftlbs. And that's it, took my Jeep buddy and I about 4 hours and 3 Beers.

 

x2
on the flowkooler....pricey but well worth it, anything you can do for the cooling system the better....3 row rad, even some minor polishing/grinding the inside of the thermostat housing for improved flow is better than not doing anything, naturally a lower temp thermo too. I purchased my highflow housing, it is nothing but a stock housing that is dremel-ed out.

 

4hrs?
you sure there was only 3 beers then!

waaaay to easy to replace....just make sure to scrape all the old gasket off, stuff a rag in the hole and use a razor blade to clean it off. the last thing you want to do is do it all over again!

 

Would have had way more than 3 beers, but I had to go to work right as we finished the job

 

How much coolant did you have to drain?

 

Not meaning to threadjack, but I am finding this interesting since I had an overheating issue last year and am curious.
If the 4.0 was designed to run at a certain temp, thus a 195° t-stat, why do some go to a lower temp stat? I can see improving the cooling efficiency of the 4.0 with a higher flow pump and a better radiator, but to actually lower the designed operating temperature I would think would come at a price for engine efficiency.

Just curious.

 

that will be correct.

 

The 195F t-stat is more about tailpipe efficiency, than engine efficiency, IMHO.......after all, their use goes back to the '70's when EGR and cat converters 1st appeared. A number of modern engine designs use lower temp factory t-stats. Two that come to mind are our 1.8L Toyota (180F factory t-stat) and our 3.5L Honda VTEC (170F factory t-stat).

 

Sharpshooter....

check your lower radiator hose to be sure it has a spring in it and is not collapsing. Although, I like many have had some cooling issues with the XJ, I have seen cars have the exact symptoms you are referring to when the lower radiator hose collapses at RPM....just one more item to check

 

Gonridnu, thanks for the tip. My lower hose does not have a spring, although it is new. I'll definitely check to see if its collapsing. Any idea where can I purchase one with a spring?I drove about 20 miles or so yesterday and was very easy and the temp stayed down for a while. It really started climbing when I got on the throttle pretty good. Temp got up to around 240 by the gauge and was very slow to come down. I actually ordered a 3 core radiator today from the Radiator Barn. Maybe this will help. THe only thing left will be to replace the water pump with a flowkooler unit.