I just installed new lifters, pivots and cleaned up the motor. Also new head gasket and coolant. Well, my old temp sending unit on the back of the motor for my guage was broke so i decided to replace it. the new one looked identical but when the jeep was all together as soon as it would get warm the guage would peg out! Scared the crap out of me. I reburped my system and checked the oil many times thinking something major was wrong. Well, low and behold i put my old sending unit back in and it reads the right temp. The box says it fits a 2.5 but the site said that it would work in both a 2.5 and a 4.0! WRONG!!!! So if anyone that has a 2.5 wants a new sending unit let me know. lol. I can't take it back because it was used for about 2 mins. I wanted to post this in case others have this problem. I would suggest checking your new sending unit.
I have a 1995 4.0 yj.