Overheating
 

That could have been a stuck thermostat, or it could have been a head gasket letting go. I have read (but have not verified myself) that the entire cooling system can be replaced for about $200, so it does not make any kind of sense to risk trashing an engine by overheating it.

I suggest the first thing to do is to verify your head & head gasket integrity. You'll need an exhaust gas test kit. This will tell you if you have exhaust gasses in the coolant. If you do, it's time to pull the head to see if it's the gasket or the head itself.

If you don't have a head problem, it's time to clean up your system. Likely you have a few components which are shot. Water pump, fan clutch, hoses, thermostat, and yea, probably the radiator. A lot of folks here swear by the Autozone Specter. Lifetime warranty. You can buy better quality radiators, but you will pay through the nose and not get that warranty. Use a good quality T-stat. Some people swear by Stant, some swear at them. ;) Nobody complains about Mopar, except the price. But compared to a trashed engine?

How's the color of the coolant? If it's brownish, you should flush it well BEFORE you replace things. Drain the existing coolant, fill with distilled water, and a good flush product from the auto parts store. Drain, replace the needed components, and refill with distilled water. Run it that way for a week to make sure it's all very clean, then drain and fill with coolant.


As for "upgrading", no need. We have several members here who live in very hot climates who have stock systems and zero problems. If it's in proper working order, the stock system will handle anything other than slow rock crawling in desert temps. Those folks do need to look at upgrades. The rest of us, no.

Did your system boil over?

Check the coolant for an milky residue and the engine oil for any signs of coolant.

If that is fine spend $40 and replace the Thermostat and the Radiator Cap.

The drive it till it fails again.

Alas, a lot of people have had head or gasket problems and never see any sign of coolant in the oil. The exhaust gas test is conclusive.

I agree with mark. One of the purposes of this site is to troubleshoot before throwing many expensive parts at something or 'driving it till it drops'. Do a radiator flush first thing. ChrisFiXx has a good video on youtube. Took me 1 day and 40$. My baby has never run more consistant temps.

I did a block test on my '00 not to long ago. I sucked some anti-freeze out of the radiator and let it get to operating temperature. Did the test. Fluid stayed blue. Cause problems could show up when the engine is real hot I let it idle for about an 1 hour in the driveway. Put fresh fluid in and did it again. Still stayed blue. Then my buddy joking around says let's put it near the tailpipe and see what happens. https://cimg5.ibsrv.net/gimg/www.che...ce35a97e5f.jpg
https://cimg7.ibsrv.net/gimg/www.che...3303432526.jpg

Just testing. I have the infamous 0331 head in the '00. Always been a little nervous about it. The Blackstone Labs test was inconclusive as far as if there was anti-freeze in my oil. Been toying with building an engine. Got a buddy who can handle this and I would be able to be part of the process. Figured it might not be a bad idea to see if I could get a handle as to what condition my engine is in. So I went to town on tool purchases. Compression tester. Which I have done. Got good readings. The block tester. Which came back fine. Coolant pressure tester. Discovered a minute leak from the thermostat housing which I took care of with a new gasket. Going to do a leak down test soon. And put a mechanical gauge to her to see what my oil pressure really is. Still might build an engine. Not a stroker per se but maybe a little somethin' somethin'. LOL.

I put 302k on my 00 TJ with the 0331 and it never failed. To this day the engine still runs great.

If your block test didn't show any problem and the oil analysis didn't come back with a problem I'd leave it alone until it cracks or there's a good reason to tear it down and rebuild it. However, if you're going to tear down a perfectly good engine, you might as well go all in. :)

I would build a completely different engine. If I did this. Which so far, cause of the tests I have run, seem unnecessary. Would try to find a lower mileage '99 down block to use if I did. In my travels I have come across a couple TUPY heads. One from an '04 Grand Cherokee that the top of a piston was broke in. Paid $50 for that one. Picked up another for free from a later '02 TJ. My logic for the '99 down block would be cause heads in those appear to be less likely to crack meaning less of a chance of anti-freeze getting down there and trashing internals which hopefully means better shape and less work for the machine shop. Turn it into a distributerless one. I already scoffed the computer and wiring harness from a Federal Emissions '00 in the boneyard for $50. Can't tell you what I might do with that. Wink wink.

I agree, flush the system really thoroughly and maybe just run straight water with a coolant flush for a day if you can. Backflush the heater core too.
Then change the thermostat, rad cap, and burp the cooling system. Top it off and keep an eye on the fluid level

If you see the temp hit 1 tick past the middle, you need to go A/C Off, heater on full hot, blower on full, and engine RPM to at least 1500 to start dumping heat out of the cooling system. Avoid boiling over, its really bad for the head and head gasket.