I haven't been around the XJ's for very long...
This is only the 4th XJ that I am building (I guess I should have wised up by now, just shows how stupid I really am).
#1 was a 1984 (V6) wrecked by a drunk driver (burned up), #2 1991 (I6) stolen & recovered stripped, #3 1995 (European "van" 2.5L TD w/5 spd manual) given to oldest son who's still rock climbing & hunting with it, & #4 1999 (I6) is in progress. Only the diesel doesn't have overheating issues.
At work, all of the XJ 4X4's that I had in our fleet had overheating issues (we had 12 in our District alone). All of them had an A/T & A/C. They were diligently maintained on the factory schedule at the dealer!
Every single one of them had issues with overheating, especially when crawling on 4X4 Low with the A/C on.
We attach a 1500 pounds of bumpers, winches, racks, rails, skid plates, aux. gas cans, 2nd battery, etc. Inside we throw another few hundred pounds of gear, not to mention passengers. Then we add lift kits, lockers and change the gearing ratios, beef up the axles, and add larger tires & wheels.
Then we drop the the AT into 1st/2nd gear, drop down into 4X4 low, crank on the A/C, and creep up & down hills in 100ºF+ heat, and expect the stock cooling system to keep the temperatures down??? Who are you kidding??
Jeep's marketing department promoted the XJ for "casual off-roading" and for "snow covered highways." The XJ was not designed for
serious off-roading.
I stand by my earlier statements... that the stock cooling system is adequate for your wife & her trips to Starbuck's.
Before you place all of your faith in the Chrysler PhD Engineers, remember that they are employed by a "FOR PROFIT VENTURE - CHRYSLER" [And if my memory serves me correctly, Chrysler was not very very good at that either (making a profit)!].
The engineers are given design parameters, and and TOLD to design a vehicle that meets those goals "FOR AS CHEAPLY AS POSSIBLE." This means that they are not allowed to include a lot of additional margin for weight hauling or towing capacity, cooling, structural strength, etc. - those all cost money & fuel economy.
This is why we got plastic radiator end tanks, integral transmission coolers (instead of big external ones), marginal gauged wiring harnesses, marginal water pumps, fluid/viscosity fan clutches, low output alternators, minimal skid protection (and it was "wimpy" when offered), 2 row radiators, cheapo thermostats, restrictive exhaust system, and a weak uni-body frame.
It was all about COST.... this is why the Military versions of Jeep vehicles are so sought after. They are built to the buyers specifications,
not some executive's bottom line!
Even a properly cared for & well maintained
marginally designed cooling system cannot handle the stress we place upon them.
Think about what you've done to your "race engine" that is keeping the temperature down:
larger oil pans
high volume oil pumps
oil coolers
roller rockers, upgraded bearings, pistons & rings (reduced friction - less heat)
installed a header & free flow exhaust
removed your CAT
high flow water pump
hood scoops (increased air flow)
and then you drive at 100mph+ (increased air flow)
Plus a lot of "racers" have stripped a lot of stuff out of their rig: stock dashboard, rear seat, passenger seat, headliner, carpeting, plastic trim, heater/defroster blower, heater core, center console, stereo, rear hatch, spare tire & door glass. Some have even removed the doors!
These rigs run a lot lighter & faster (and therefore cooler) than rock crawlers or hunters loaded with gear.
If these "XJ's" didn't need so much beefing up & work, we'd all be rich(er) and have free weekends to enjoy them in the countryside!
AND you wouldn't be here on the forum!