Still not fixed right

Got the Jeep back last night.  The dealership finally sent it out to Brakemasters on Monday, and called me on Wedneday to pick it up.  They replaced the front rotors & pads, and put in a new water pump.  Didn't touch the thermostat, apparently... 

As I was driving it out, I put on the air conditioner, and the compresser started screeching pretty loudly... so I turned around and pulled right back in... and that's where it sat.

We went immediately to the dealer, where I finally spoke to the owner.  While he was quite good at telling me how much money he was losing on the deal, he couldn't argue the facts:  I bought a vehicle to use as transportation from them, and so far, it had only spent one night in my driveway after two weeks...  So... they set me up in a loaner for the night while they tried to get a new compressor over to Brakemasters.

Thursday night, I picked up the Jeep for the second time in two days, and finally was able to drive it home.  I decided to take the long way, so that I could speed test it on I-10.

Ten minutes of stop/start at 45mph.... no problems.  Temps stayed right about 210F.

Ten minutes of 65mph on I-10.... Temps rose a bit to 215F, but stayed steady.

Eight minutes of 45-50mph on Tangerine... DOH!  Again, I get the chime and the temp gauge runs up to 240F.  Turn on the heater (which now works), and after about 60-90 seconds, the temp drops back to 215F. 

Three minutes later, go thru the same cycle, although this time I was able to park it for a few minutes.

Driving home, no more occurrences, however the "Check Engine" light came on, and wouldn't clear...

While researching the overheat problem on the web, I stumbled upon the North American XJ Association website, which is a group of Jeep Cherokee owners.  On their tech discussion forums, I found several other owners who had reported similar problems.  The most popular solution was replacing the radiator, although a few had to replace the cylinder head -- cracks were allowing exhaust gas to get into the cooling system, which caused hot air to be trapped inside the block....  Apparently, the 2000 4.0L engine has a history of cracked heads, but I'm not seeing evidence of that just yet (although it could be and just not visible).

While they've tried to put Humpty Dumpty back together one component at a time, the mechanics who have looked at it still haven't fixed the initial problem...  So, back to the dealer again, and  I'll propose a new radiator based on this.  They're not pleased about being held to the warranty, but it wasn't marked "As-Is" so as long as they can be held to that, I will do so.