XJ Over heating

[Loganwayne]

i got a 92 xj inline six was told the motor was out of a newer model or rebuilt. either way driving around town ran fine, but take it off road and go slow putting a little strain on the engine it would quickly heat up. i put a 160 degree thermostat on it that stays open replaced coolant. the electric fan didnt have any power going to it so i wired it to come on at start up and stay on. thought all this would fix it took it out today and it was still getting hot not to the same degree as before but i pulled a maybe 100 yard hill and it almost got to the red any ideas on what could be going on or not working right or any thing i can do to help keep it cool. thinking about replacing the radiator with a bigger one

 

[RenegadeT]

have you pressure tested it...make sure the cap is holding pressure? A coolant pressure tester can be borrowed from AutoZone, it should help find if/where you're losing pressure. If you have the radiator with plastic tanks, a common leak point is where the tanks are crimped to the aluminum center section. Mine was leaking there (high up, pass. side, right under the rad. support), and I rarely saw any drips, but with the tester hooked up, could hear it hissing out.

 

[a_kelley]

look here and read through.. http://nc4x4.com/forum/index.php?threads/beat-the-dead-horse-overheating-xj.96973/

if it is a newer motor, look at the temp sender on the back of the head. it should have a push on connector with screw threads on the sensor. if its a white block connector, you have the wrong sender. mine was "overheating" but really it was just the wrong sender. (read the thread you'll find out how i figured that out =X )

infrared thermometers will tell you if it is actually overheating.

pull the cap and look for bubbles or black residue.. or hook up a pressure gauge and see if you rev it if it pressurizes really fast and the needle flickers (blown head or gasket into water passage from combustion chamber).

redneck pressure test: feed 15psi compressed air in through the overflow, it will push water out if its leaking.