On your way to the gas station, see how it does! May just be how your gauge reads..

 

The exterior of the tstat housing will not be the exact same temperature was the water. Expect it to be a 5-10 deg F lower. And pyrometers aren't as accurate as people assume.

With that said, for your XJ the coolant temp sensor for the gauge is at the back of the block. So that is another reason why the temperatures can be different.

 

Yeah I'm expecting it to not read exactly but it doesn't seem to be anywhere close to what my gauge reads at all. My gauge is saying the temp is in the 230s. I'm gonna drive it around tomorrow and take some more readings but it kinda seems like the gauge is not reading correctly

 

The rear of a straight 6 engine is always hotter than the front. With such a long engine it's difficult to get perfectly even coolant flow throughout.

Had a couple of jeep 4.0s, a Ford 300, 2 Toyota JZ engines, and 2 cummins diesels. All of them hotter at the rear.

Your gauge may be close to accurate but that doesn't mean it's telling you the exact engine temp. It's only reading the rear of the head, which is a hot spot.

 

I was shining the laser back there and none of the readings that I was getting at the sensor and the area around it in different spots in the rear but none of my readings were even close to what my gauge is reading they were all around 190. 200 at the most. I'm gonna drive it around for a bit and see what happens and take more readings when I stop to make sure. Is there a way to test the sensor to make sure it's good. I would like to just replace it but I'm gonna have to take the valve cover off cause I can't get a socket around it, it's in the way just barely

 

That's reassuring!. Swapping out to a new sensor might make your gauge read differently. Clean the electrical connection at the sensor while your at it.

I'm not familiar with the 96 and down version of the xj. (Only had a 97 and a 00) Cleaning your electrical connection to the gauge cluster or any grounds you find under the dash is always a good idea though.

 

I drove around for a bit today and the gauge was reading about 235 the whole time, the car ran fine and sounded fine. Didn't overheat at all and I stopped twice to check the temp with a laser and I was getting the same kind of readings that I was yesterday. Nothing close to 235. Thermostat housing is about 180 190 and the rear where the sensor is around 190 195.

 

Sounds like your gauge is just reading a little higher than actual. Which is better than the opposite.

Glad you're not overheating and its running good!

 

So I replaced the valve cover and got that sensor while it was off. Changed the pcv and ccv valves and grommets also. Jeep is still reading higher but now it's lower and will sit after 210 while I'm cruising and sit in between the middle tick and the tick after. Im still getting temp readings with my laser thermometer showing the correct temp all around so I'm thinking my gauge is just a little inaccurate probably. I'm just gonna live with it for now. If it starts overheating the gauge will start going up but it stays consistent just not where it should be

 

Sounds like your ready to and maybe ready to install a temporary gauge (new one ) to see if your dash gauge is good/bad.
I would at this point . use the IR gun also.
I would paint the thermostat cover black and use an IR gun to read the results before and after looking at the dash gauge and the external gauge temporarily in for this test.
If you pull the 2 wire from the sensor up front the ECU will turn the fan on...the sensor at the rear of the head is wired to the dash gauge. Pulling it off , and grounding it ,will open the circuit and the needle will go all the way clockwise.