[BlueMonster]

Well I know it's not the gauge/sending unit, because I used a mechanical gauge that I bought at the store, and it also indicates that the engine is overheating.

I have tried 4 different thermostats in total. 2 GM and 2 from the local parts store, including a 160 degree thermostat. I know it's not supposed to use a 160, but I tried it just to see what would happen. I overheated, but not as badly.

My Jimmy doesn't have any bypasses except for the overflow bottle, which is in good shape.

I also did check the radiator fins to make sure that they were all good and not obstructed. I even did a test. I started it up and when the fan came on, I put stuff in front of the rad behind the grille. The air moving through the rad sucked the stuff up against the rad. So I know that air is flowing really well through the rad, because it was able to even suck my hand up against it when the fan was on.