overheating at idle

I think your late model XJ the aux fan no longer runs when the a/c is turned on; the aux fan is controlled completely by the PCM.

I would, for grins and giggles, unplug the aux fan and jumper it to the battery to make sure it actually works.

220 degrees isn't bad, I believe the PCM is going to turn on the aux fan at 217 degrees or thereabouts, and the dash temp gauges aren't direct reading either, the info is coming from the PCM too.

I would pull the CTS--coolant temperature sensor--out of the t/stat housing and clean it up with some crocus cloth, put it back in and see if that makes any difference.

Are you aware of the 0331 head issue with the late XJs? If not, do a search.

Good luck.

Yes I'm all aware of the 0331 head cracking. it scared me when the thermostat locked up, but its yet to show any symptoms. I'll try the cts tommorow. I know 220 isn't HOT but my jeep used to run 210 all day every day, and now somethings different with the temp.

Ok. The thermostat you used could be off a bit or just different enough from the old one to show a difference. BTW, what temp/brand did you install? I only recommend and install Stant SuperStat Premiums, 195 degree for the 4.0 engine.

Also, when was the last time you replaced the radiator cap? Good for about 2 years and then should be tossed. Get a 16 lb cap, the counter monkey will want to sell you a 13 lb cap but insist on a 16 lb--if they won't sell it to you start buying parts at a different store. Don't use a lever-type cap.

Next time your engine is good and warmed up, try parking nose-up, that should help any trapped air to be forced out.

Post up how it goes.