my jeep is overheating only on long highway drives or if it is standing still for long periods of time.

last time this same problem happend and it ended up being the waterpump not circulating the fluid. i got a new water pump about 2 months ago now its starting do do this again... ive replaced almost everything. you can feel the top radiator hose get scorching hot and rock solid as if the fluid is jammed somewhere. the blades on the water pump fan thing were like melted off so the fluid wasnt circulating i wonder if they melted off again or if something is bad such as the radiator.

 

What have you replaced?

 

a malfunctioning fan clutch?

 

This^ ..... you say long drives is it while driving or when you slow down? it sounds like fan clutch isnt working. when its warm and you shut the engine off the mechanical fan should stop almost immediately if good, if bad itll continue spin once the engine stops or you can turn it when cold by hand then let it warm up and then it should be noticbly tighter to turn by hand

 

i was thinking it was one of the fans or something but that wouldnt cause the fluid to be backed up and pressurized!? last time i had almost the same problem and it ended up being the water pump but it was JUST replaced i dont see how it can go bad already

 

i have replaced everthing involved in the coolant system besides the radiator, but i did run a hose through it and it looked fine

 

the radiator cap should vent to the bottle when pressure gets to 12-16 psi. By your descritption you either have a faulty fan, T-stat. I would change the T-stat and radiator cap to what ever is specified by Jeep, even if you just did them. I would also verify the fans are functioning, the mechanical fan clutch in particular. Your E-fan should start with the AC/Defroster and when temps reach 212 degrees. The fan clutch should be at its tightest when ambient temp is over 170 deg.

If it is not one of these it will be the Radiator or pump.