Overheating...gee who woulda guessed

i have a 1992 jeep cherokee laredo. its got about 180000 miles on it and i recently replaced the tstat and all the hoses to the radiator and it is still overheating. the other day it overheated and fluid was rushing from the radiator to the over flow bottle after sitting for about 10 minutes it started bak up and was just fine. it only over heats sometimes. also fan only comes on if heater is on. what is wrong? im goin insane tryin to figure it out.

Does it over heat when your heater is on? Sounds like your fan is not working right> If iam right you have a Viscous Fan Drive which acts to temperature increases. The fan should be turning all the time and when the fan senses heat it will kick in at a higher speed.

There is a sensor that turns the elec. fan on/off. Sounds like it either bad or you have a bad connection. I believe, on your model, it's located on the manifold.