Engine Stall

My wife owns a 99 Grand Jeep Cherokee that up until this point has been a fairly reliable vehicle with few problems. Roughly, a month ago we started having overheating issues that I traced to a faulty cooling fan relay. Unfortunately, before I could replace the relay, the engine was left ideling with the AC on. Needless to say the engine overheated and has been running poorly since. The Jeep can only be driven for roughly 2-3 miles before stalling (usually at a complete stop) and upon opening the hood, the engine is well above normal operating range (220-240 F) this makes me think that the problem is related to a thermal condition. Although I haven't been able to reproduce the sound, my wife tells me that a metalic clicking sound can be heard shortly before the engine stalls.
I've checked fluid levels; coolant stays constant and no watered down oil on dipstick.
At this point I'm looking for a few ideas other than the dealership who seems to think that a microscopic radiator leak might magically solve this issue.
Thank you.

I'm thinking the thermostat might not be opening. I'd run a test in the front yard, start it up cold with radiator cap off, let it run and see if the fluid moves through the radiator.