Maybe pull the plugs and check for one cylinder to be steam cleaned. After 400,000 on a diesel, ive dealt with many head gasket issues and temp spikes. Not all resolved.
Thank all of you for your questions and advice.
Fans
Fair point. The fans I have felt are indeed blowing toward the engine. The setup for 2026 was a single core aluminum radiator with three electric fans. Two on all the time. One on at 218 F. The fans are definitely affecting the temperature downward. However it was concluded these are underpowered and I have concluded the cap blew the hose clamps. This week I will have a new fan clutch, fan shroud, electric fan, and dual core radiator (stock).
If that isn’t enough
I am considering a pusher fan in front of the radiator but this morning I am considering instead mounting it to the hood without any holes but blowing downward.
I’m also considering a cool air intake modification because all of that heated air under the hood is going into the intake manifold.
Because of the radiator cap causing coolant to exit:
Coolant added daily if needed in small amounts
On the oil and coolant I check these religiously on all of my vehicles before leaving. Over time between two oil changes in 2026, I had to add a few pints at a time to the overflow. Ultimately consuming a gallon between oil changes. Agreed if I did not check very frequently I could be driving low on liquids. This rig is in the shop 9 months of the year. The chances of all new coolant is likely with the fans and radiator and pump and thermostat changes as often as three months over that past 2 yrs. Point received. And very valid.
No rough idle
Agreed if one cylinder was not firing temporarily I would feel it. Interestingly a 2000 Cherokee when 210 F can turn it off. Go into a store. For say ten minutes. Come out and start it and it runs rough, almost choking, cause the fuel in the rails is boiling. Does this until the coolant moves and fans cool it back to 210 F and then it runs perfectly normal. No CEL.
This 2001 has not once ever done that. Nor has it reacted ever to any heat condition nor running rough, shaking, no strange noises under the hood, no growling or any indication from performance it is hot other than gauge to red and “check gauges” suddenly. The shop verified 240 F with a heat gun and believes the heat sensor in the thermostat is correct and does not need to be changed. They are treating the temperature very serious which is why the fan configuration keeps changing which requires radiator changing.
What I’m trying to illustrate is it’s almost as if one part of the engine only. Let’s say only the part near the thermostat housing only is 240. Because how can the whole engine operate as if nothing is misfiring. As if the fuel is not boiling in the rails. And then with the hood up the temperature corrects within 1 minute with the engine off. As fast as it climbed.
It heats up faster than a gas grill. As a surprise from 215 or 220 F and next second “check gauges”. There is no gradual climb to 230 F or 240 F to get some beads of sweat. It’s straight panic. “Check gauges.”
So that’s how come this morning I’m thinking of a pusher fan attached to the hood blowing straight downward past the fuel rails, exhaust manifold, pushing the air in the compartment to the street. Or maybe a pusher fan in front of the radiator or both.
I don’t want holes in my hood because of rain.
I wish I could buy a Jeep hood like a Challenger or Charger with a cowl in the back of the hood to allow heat to vent.
Thank you, yes, there have been cameras down all the cylinders looking for steam clean and on the plugs. No white smoke coming out the exhaust.
I really don’t understand why you are keeping this vehicle.
Some people just don’t like to give up, and once you get this far invested into something, you tend to want to see it through till the end… Not everyone throws in the towel whenever a problem occurs…
Back in the day, it would be my mission to find the issue… I liked being a problem solver, figuring out the stuff other shops gave up on…
I’d place a shop rag etc in front of the radiator to confirm it is being sucked up against the radiator, one fan at a time… You could have one fan pushing and one fan pulling, and it feel like both are moving the air the same direction…
I don’t think a fan up against the hood blowing down will do anything more than to push more hot air down on the engine, if anything, I might try to raise the back of the hood as high as the hinge will allow to try to move as much air out from under the hood as possible… or louver the hood…
If your next adventure doesn’t work then I’d probable go back to all stock parts and start over, checking everything, like flow rate, and put a pressure tester on it (engine cold and not pressurized) then start and warm the engine up and then raise the idle up to 2,000 to 2,500 rpms all while watching the pressure the system is operating at from cold to hot and back to cold again…
I would also keep an eye on the engine temp at the t-stat, one side of the radiator to the other side, radiator hoses including heater hoses, as well as each cylinder using an infrared temp gun…I would also have Live Data on a scanner running to confirm what I am seeing is the same thing the ecm is seeing…
Put a fuel pressure tester on it as well to see if the fuel really is vapor locking…
The pressure tester like I mentioned will show you the operating pressures, when the t-stat opens, when the fans come on/off and if they are helping any, as the temp raises so does the pressure, as the temp drops so does the pressure…A coolant pressure tester can make a great diagnostic tool, on top of just simply applying pressure to check for leaks…
Have you joined all the XJ forums you can find and posted your problem there? And please make your first post short and sweet, lots of folks don’t have a lot of patience in reading long posts. A summary list of symptoms and a list of what you’ve done.
Of all the systems on a vehicle the cooling system is about the most straightforward.
I hear you
But it’s also important to be able to realize something is an unreliable financial money pit and it’s best to move on
“I’m going to fix your car no matter how much it costs me!” 
I often had the same attitude, but remember we go to work to make money, not make friends. Seems like once you get the reputation of being a problem solver, you get more problems to solve.
I keep seeing mention of the temp going up/down instantly, That’s pretty much impossible.
I suspect a faulty temp sending unit or possibly gauge.
Check to see if the following deflector is still there. On my sister’s car the air deflector had gotten knocked off and her car would overheat. when the new one was put back everything went back to normal.
the 2001 Jeep Cherokee XJ does have an air deflector as part of its front bumper system. In the 1984–2001 Cherokee XJ, the front bumper assembly includes an air deflector (also called the front bumper end cap) that is fastened to the bumper and body side sheet metal 
www.jcherokee.com. This deflector is designed to direct airflow over the radiator and cooling system, helping to improve cooling efficiency, especially in stop-and-go traffic.
The air deflector is part of the bumper’s front section and is mounted to the bumper beam and body rails. It works in conjunction with the radiator shroud/fan guard to channel air toward the radiator fins and away from the engine compartment.
Also, i never used the following but you can try it to see if it helps. it is supposed to be safe with all types of antifreeze.
Some people don’t know what is relevant, posts get cluttered with talk about spark plugs, cold air intakes or the spring inside the radiator hose.
Then the talk about mounting a cooling fan on the hood; mounting a fan against a solid surface will not provide air flow. Like when a box fan tips over onto the floor.
Electronic gauges are designed to show “center” position from 190 F to 229 F, at 230 F the gauge will move to 3/4 position.
Sounds deceitful, but modern vehicle cooling systems operate in a wide temperature range, drivers can be distracted by seeing the gauge move from 195 F to 210 F while at a traffic light and believe there is a problem.
Did your sister’s car have a conventional grill? SUVs normally don’t rely on under-bumper air dams for cooling.
Bumper end caps? Those maybe for aerodynamics but not for the radiator.
Thank you for these tips weekend-warrior!
I know that one type of cooler running antifreeze was tried in Jun or Jul of this year with no effect.
It could very well be when my radiator got a hole in it three years back, they took this part off and did not put it on – I don’t have it here to look at.
Is this the part that you mean? Does it sit on top of the bumper making it so no air slips under the radiator without going through the radiator?
Thank you davesmopar for these suggestions! I will make sure to request them of the machine shop.
I agree with you It_s-Me as I have written already. Have you seen where a faulty temp sending unit or gauge in the console was bad and after it was replaced there were no more 40 degree spikes?
As far as the gauge on the dash it seems “instant”. One moment it’s 215 and the next ‘update’ to the temperature from the PCM it’s “Check gauges” without any other symptom whatsoever. Or climbing. It’s not 5 degrees. It’s a 40 degree change. The shop says it is real as they have recreated and measured high temperatures with heat gun. Aimed at the thermostat housing. So they do not believe it is a faulty sensor / sending unit in the thermostat housing. If it were you, would you proactively change the temperature sending unit / sensor?
It is also just as surprising that turning it off, opening the hood, and turning on the key so all three fans blow that the temperature drops back to 210 within one minute. The shop says it sounds like the fans are doing their job. Is the increase in heat impossible or decrease or both? Or is it just a delay in the PCM frequency of updating the console gauge?
The shop that put a hole in my radiator was a Chrysler dealership that is no longer in business. With a kid right out of high school who was the tech. After he damaged my aluminum radiator with a hole, a new fan shroud and new radiator was put in but it has never been the same or run at 210 F again since that day / week in their “care”. Since then it not only runs hot to me all the time over 210 F but it has random heat spikes of 40 degrees from center. All the way to “check gauges.”
After the engine was pulled and rebuilt, first thing that was changed after that was the fan clutch. I additionally had four coolant hose leaks losing coolant this year and still have random misfires on up to four cylinders simultaneously turning on the CEL for almost three years of misfires. I believe the leaks and misfires are related to the heat whether the cause or effect.
Yes there comes a point to end it all. After my third diesel engine, i sold it for $200 to the guy that put my last engine in. Heat spikes. He did the head gaskets and then called me when the temp still spiked. Wanted to know what to do. Like you are asking me? Sell for scrap. New tires etc. Maybe all along the block was compromised, or another radiator, hose, who knows but not my problem. $10,000, 20 years, three engines, several head gaskets, im done at 480,000 miles. Felt good. Waxed up my riviera.
Appreciate your advice for when to call it bing. There will come a point. All parts under the hood are under warranty at the current place and they are convinced it is solvable and committed. They do not want the temperature spiking ruining their work they have done any more than I do. I don’t even have near half the mileage you got out of your diesel. Nor do I intend to. It will feel good one day to drive it again in a reliable condition and enjoy it, or sell it for someone else to enjoy, or part it out with a dead motor. Right now, it is still in progress. The current belief is the fans are underpowered.
Imo, you either need to pull the plug . . .
or find a better shop, as has already been suggested
The vehicle would not be drivable on 2 remaining cylinders, when do the misfires occur? While accelerating? At idle? During start-up? When the engine is hot/cold?
That topic may have been based on the 1980’s Camaro, the car had very small grill openings and relied on an air deflector below the radiator core support for air flow at highway speeds.
