That is way too hot to be driving around. Holy ****.

Is the electric fan coming on at all?

Get the cooling system fixed before you cook something.

 

E-fan is 6 months old and runs as it should. Fan clutch about 2 years old and has the right tension. Gauge in the dash is obviously not giving me the right info. If you look back in the original post you can see all of the things I have or had have done. I keep up on all the maintenance. Did the heater core a couple years ago so it is in really good shape. I was just in Lone Pine last Sept driving through 115 degree heat with my a/c and wasn't having problems. After that trip we discovered that the T stat was stuck half open and I let a shop replace it. I also let them replace my temp sensor at that time because they said the wires were a little ratty. They ended up accidentally putting in one for a Grand Cherokee... but they did f ix it for me. And I do run a 1 6pound radiator cap.

 

Confirm the temps with an IR gun.

I just replaced my dealer 195 thermostat with a Stant 180 thermostat. I run about 200 now in the summer. I had ordered 2 different Stant thermostats from RA - one was 195 and the other 180 (the ones with the V notch). I tested them by boiling them in hot water first. The 180 thermostat opened up way more than the 195, which I assumed is the reason why I am running cooler. I would try that first, as it is cheap to do. And you should definitely test the thermostat before installing.

 

I always do! My Pops taught me right on that. This last one was installed by a shop though. I am just at a point in life where I don't want to do the work as much and I thought I would let a shop do it. As a female I usually get the runaround at shops so have stayed away from them most of my life. I guess I need to go back to doing the work myself.

 

Did the shop do a flush & fill on your Jeep, or did they do a drop & fill?

When was the waterpump last replaced? Maybe the impeller has corroded? Was a quality thermostat installed? What brand? A shop will tell you they installed a quality part, but it might not be a quality part / known brand name.

How do the fins look on the radiator?

 

I'm looking through my purchase history and it may have been longer than I thought for the water pump. Possibly 5 years? Don't know what brand they used but I can find out. I actually stopped at the shop during one of these episodes and he ran out and put his reader on it and was getting the same readings as me. yet the jeep sat there running/purring along with the a/c and reading high temps both digitally and on the gauge. His only thought was to replace my T stat again and re-flush the system. I have a working/business relationship with this place so i believe him when he says they do a thorough flush. My fins are pretty good, Not pristine. It was super dirty a few weeks ago with bugs and I hosed it off. Also the system holds pressure.

 

If it was me I would get rid of that aftermarket radiator and go with a Spectra factory replacement, it is likely that the radiator is your issue. Very few aftermarket radiators work well with the XJs cooling system.

 

How are you not boiling over at 257*F?

As a test of the t/c lockup, drive along steady at highway speeds, and lightly tap the brake pedal with your left foot. The rpm should jump a few hundred rpm when the t/c unlocks.

 

Might want to consider it as a possible problem. They don't move a lot of water when they get like this. Just enough to fool you.

 

I know, right? I do not understand what is going on. It was baffling the mechanic too. And this is only happening when its hot outside. Ill try the brake trick this morning and let you know. I don't know what other diagnostics i can do.

 

Hey guys. Thank you for all your help! I finally found the culprit. It is a tiny leak at the T Stat housing. I am so disheartened with trying to find a mechanic. I guess I go back to doing the work myself... I am going to replace the housing and the T Stat just in case the housing is warped or something. This should cure my weird running hot issues. I can say these Jeep's are BEASTS! Takes a licking and keeps on ticking. I cannot believe it wasn't actually boiling over, haha.

 

So you do yourself a favor. Use a FelPro gasket for the thermostat housing.
Do not use the paper one that will come with the new thermostat housing.
Clean it all up nice nice. Get that channel that the thermostat sits in good and clean too.
Do not use any gunk.
It will be awkward getting everything to stay in place without a little gunk.
But can be done cause I did it.
Cause if that thermostat slips out of that channel, you don't notice it, torque down the bolts, you could crack that housing.
Also when you swap your sensor from the old housing to the new one don't forget the thread sealant.
I used this one on mine.

https://www.napaonline.com/en/p/PTW7651155

You might be able to use teflon tape but I did not.

 

Glad you found the problem. I'm sure that water pump wont be the best on the inside.

Be careful with the heater core hard line that comes out of the water pump. They can be brittle and easily bent.