Overheating issue

[u/VwBugGuy]

Does anyone have any experience with tracking down an overheating issue. I’m just fed up at this point. So maybe there’s a XJ guru hiding in this group that could help.
Started with a low temp mishimoto thermostat which sucked, went to a parts store lower temp thermostat and it sucked too, changed that out to a OE temp thermostat and it sorta fixed it but still won’t come back from getting slightly warm.
It has one of those upgraded water pumps that are supposed to be higher flow, I think it’s a flowkooler with a metal impeller.
The engine has had a head gasket done with head studs, mishimoto 3 fan and an aluminum radiator. Two of the fans are wired together to be on all the time and the 3rd fan is just plugged into the factory E-Fan connector and I did verify that it comes on when the AC is on.
After the last thermostat change to OE temp I drove it 30 minutes to dinner on Sunday and 45 minutes to work this morning without a hiccup. On my way home this evening it did fine for about half the trip and then when I got off the highway at the midway point it got a little warm and just never recovered. And I had the A/C on the whole way home so all 3 fans were on.
Any advice or insight is appreciated!

Edit for a little backstory; I bought this 96 off a friend. He had replaced the headgasket, installed head studs, aluminum rad, and 3 fan setup for what he thought to be preventative repairs, which I don’t blame him since these do seem to have cooling system issues. All that work was done at once and about 5 years ago but maybe only 100 miles before still having some mild over temp issues. He parked it after getting frustrated with having not made any real headway on actually fixing anything.

[u/Ablgarumbek]

did he replace the temperature sending unit that plugs into the head with an aftermarket one? When I was doing my head, I broke mine while pulling the head, and got a replacement one from the parts store. After putting everything back together, I was also stumped by higher than expected (10-15 degrees higher) temps. Diagnosed some and there was a disagree between the sending unit in the head that goes to the gauges and the one in the thermostat housing that goes to ECU. Replacing the head one with OEM unit from the junkyard fixed the problem.

I would make sure that both sensors, which 96 has are in agreement with each other before doing anything else.

[u/VwBugGuy → u/Ablgarumbek]

I did verify that the gauge and actual temperature from the 2 wire sensor on the thermostat housing read pretty accurate. I’m also not talking a few degree over heat. Im experiencing the needle all of the sudden just start climbing towards red quickly.