OVERHEAT

JUST replaced radiator,water pump, tstat from dealer and fan clutch.my mechanic said the elec. fans are working properly. When a/c is on in bumper to bumper. it is over heating .AS SOON asi turn it off the temp comes down in about 30 seconds. Any ideas ?

There any many people on this forum who agree that the XJ cooling system is barely adequate, and possibly bumper to bumper traffic with the air on is asking too much. My '96 runs at the warmer end of normal, and the cooling system is in good health. Back when the A/C worked, it would behave similar to yours. I almost never used it, and since it took a dump three years ago, I just can't motivate myself to fix it. Look around this site for ways that others have dealt with this problem, like hood louvers and raising the trailing edge of the hood, to increase air flow.

I would assume that the dealer would have picked this up, but here are some other thoughts:
1. Make sure they bled out all the air when installing the new radiator and refilling it. This will cause overheating instantly, kind of like you described. One way to get it out is to raise the front end, run the engine, and tap the radiator hoses with a mallet to get any bubbles out. I'm sure there are other ways.
2. Check the hoses. Make sure they are firm and not squishy. Squishy hose will suction itself shut.
3. Head gasket problems will cause overheating. Check for cracks and/or leaks.

You already did the other 4 steps of the 7 step program. I can't think of anything else. Also, do not band-aid the problem. These rigs will run at proper temps with a good working cooling system. All the Flex a Lite fans in the world won't cure the problem. Ask me how I know. :-(

What year? What modes have been made in the front area? R-12 or R-134a. Has it always had this problem since you bought it, or is the overheating new?