downs

On 2001 models it doesn't work that way. Later models switched based on engine temp only, they didn't care about condition of the AC switch.

OP since you are overheating at idle you're most likely having an airflow issue. Powerwash the ac condensor and radiator fins if you can. Check out the fan clutch. The FSM lays out the testing for it. The easy test is the "spin test". FSM says if you can hand spin the fan when cold and get 5 rotations out of it, it's bad. There's also a more indepth test involving drilling a small hole in the fan shroud to insert a probe type thermometer. Start the jeep and tarp from the grille. Another set of eyes is important here so you don't overheat the Jeep on accident. When the air temp behind the radiator gets to 190 you should have full engagement of the clutch fan (roaring air noise).

lawsoncl

Be careful with a powerwasher. They can easily bend the fins!

Randy Bobani

Exactly. There seems to be a lot of confusion on this subject. 218'F is too high.

Jake has already serviced his cooling system and he's being led down a rabbit hole filled with silly parts. With the E Fan on he will be able to sustain temps under 210'F at all times. Get a 40 Amp relay & switch harness with an inline fuse. Like a lightbar harness. Turn the fan on and leave it on. Wire in a thermostat if you like to get fancy.

TRCM

If everything has been replaced and is working correctly, then he would not be running hot.

Putting a manual fan control on it and running it all the time is hiding the problem..........period.

Will it work, yeah, but it is just masking the problem, not solving it. It will hide the problem until the problem gets bad enough it won't anymore.

Like putting on a dual steering stabilizer to hide worn tires or loose TRE's.


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BlueRidgeMark

Yep. It's not much better than removing the bulb to cure a CEL that's on.


A properly working XJ cooling system is good for all but the most extreme conditions. If he's overheating, there's a reason. He needs to find the reason and fix it.

Overheating when turned off means he's running on the ragged edge all the time. That should not be happening. He's either gettting extra heat from somewhere, or he's not getting it out of the radiator.

A flush won't clean everything out of a system.. It's likely his radiator is clogged. OR, he may have a lot of scale built up.

third coast

Let’s back up a bit and look at the initial report that it will leak at the radiator cap when shut off when hot. (when you say parked can I assume you mean engine shut off?) That is an odd situation. There are two seals on the cap. The lower seal should hold pressure until a rated pressure is exceeded and then allow fluid/gas to first vent to the overflow reservoir. The upper seal should hold unless pressure continues to rise and then it will unseat and allow fluid to run out around the top of the cap. Some things to check/recheck:

The top seal may be bad and allow fluid to escape sooner than it should. I have had a new cap show this fault. Try a new one of a different make.

Are the upper and lower sealing surfaces where the cap sets and seals into the radiator neck clean and smooth. A bad surface and crud that prevents a proper seal will cause issues. No cracks in the neck area?

Is the overflow hose securely connected near the cap and is it in good condition such that it does not leak? A problem here can allow coolant to escape when hot and allow air to enter during cooldown and result in overheating symptoms later.

Verify that the overflow hose is not blocked and preventing coolant from moving into the reservoir as it heats and expands.

Take a look to see if the level in reservoir tank increases as things heat up and falls on cool down. That would be normal. Do you see significant air bubbles or surging at the reservoir? Normally you should not.

Before you get too far off on other items lets verify what is going on related to the cap and try to understand why.