I installed a new radiator in my 88 XJ in the past couple of months. If the GFs XJ is gettng to 215 I'd think you may have a thermostat that been damaged by running warm.
I would replace the radiator with a new one. I installed a Modine this time, had a GDI last time but it came down with a leak between the tank and the fins. The modine is 2 cores which totaled 1.5 inches, the GDI is 3 cores which totaled 1.5 inches.
I heard a mechanic on the radio say a radiators life is 7 years, anything more is just gravy so you are due for a new radiator.
I'd replace these parts also:
* Fan clutch, there not good test for these and the word is they only last 5 years. This could explain why it runs warm, the fan not sucking enought air.
* Thermostat - buy a new 195F thermostat at the dealer, it comes with the vent hole and a very nice gasket with RTV pre applied. No need to have a tube on hand. Expect to pay $8-10 for the thermostat.
* Radiator cap - The spring could be heat damaged so put a new cap on that new radiator.
* Radiator hoses - I got mine at the dealer very nice. Expect to pay $40 for both hoses. The both comes with the antichafe on the outside and the lower comes with a full length spring.
* Fan belt - the radiator will be out and it will never be easier to change the belt and tension it. Also pick up a Kriket II bension gauge at NAPA. Belt tension on my 88 XJ is 180-200 lbs for a new belt. I currently use a goodyear gator back, has the ridges cut to reduce belt noise.
* Idle pulley - this may be rough and I picked up a new one at advance autoparts for $10, cheap insurance.
* coolant - use distilled water instead of tap water to mix with your anti-freeze. A guy who was a Army Nuclear reactor tech told me to use distilled water for radiators. Avoids introducing any minerals that can attach to the block or radiator and reduce how well the engine cools.
When you have the belt off spin all the accesories and replace anything with a rough bearing. Depending on the mileage you may want to change the water pump as preventive maintenance. I changed mine at 135,000 miles because I was not sure how long it would last. I installed a Hesco water pump since they siad their impeller pumped more coolant and free'd up HP and torque. You can read about them at
www.hescosc.com. I recommend you install a new water pump, not a rebuild. Also do not over look the dealer as your source for a new pump. Do get the water pump gasket at the dealer, it like the themostat gasket with RTV pre applied. No need to apply any, I installed mine dry and no leaks 2 years laters. The Fel pro looked second class compared to the mopar gasket.
IF you change the water pump make sure to loosen the water pump pulley bolts before you loosen the belt. It makes life MUCH easier to do it then than after you remove the belt.
Disconnecting the trans cooler lines will require a speical tool. It called an AC line tool, you can get a set of 6 at sears for 6 bucks, you will need the 3/8 tool to remove the coupling if it all metal. If the coupling has plastic ears then you just press the ears against the line and pull.
I hope I have covered it all.