I have a 1987 Jeep Cherokee Loredo. I got the vehicle stock about 8 years ago. it has the 4.0L and an AW4 tranny. It also has the closed cooling system with the small plastic overflow tank with a presurized cap.
I replaced the radiotor about 7 years ago brand new and all the hoses and pressurized overflow tank.
I aquired another 1990 4.0L that I rebuilt from top to bottom. It was bored out 3000th's over and that is the only change in the rebuild, Everything else is still stock.
I just had my AW4 tranny rebuilt by Jaspers and it has like 200 miles on it.
As of today I have the rebuilt 4.0L from a 1990 and the rebuilt AW4 from the 1990 currently in my 1987 Cherokee with closed cooling system. It has all new hoses and Pressurized overflow tank (as of two weeks ago). The thermostat is working, the temperature sensor on the head is new and is also working. My gauge on the dash works also ( matches the temp in the radiotor hose using a thermal gauge).
I also removed the factory trans cooloer that was installed in the front and replaced it with a brand new one that is about 3 times the size of the factory one. While doing this I bi-passed the the cooler that goes through the radiator for the tranny lines.
It still has the radiator the I purchased and installed new 7 years ago.
Now to get to the issue......
Prior to the rebuild of the drive train from the 1990 It had the 87' 4.0L and AW4. It had 219,000 miles on it and although it was tired and burned oil it never over heated. Always heated up and ran at and around 210 degrees. The temp would creep up when ever i drove long hills at higher speeds such as I-5 sisque summit or Hwy I-40. Never anything bad.
Currently as of now It starts and runs great!!!!!!
It has a ton of power and also works great at opperating temperature. It runs at about 210 degrees. I can drive it all day long on flat land and it stays at 210 degrees.
But if i drive it hard at higher speeds (60-70 MPH) and try to maintain that while pulling a hill the temparture sky rockets to 235-240 almost in the red! To maintain that speed while climbing the tranny is "kick down" thus working the engine and tranny hard.
As soon as I back off and quit working the drivetrain hard it will begin to cool back down and usually return to the 210 Degree temp. Not very condusive to driving on the freeway in southern oregon where we have lots of hills.
So I have "essentially" a stock drive train in a 1987 cherokee that over heats when maintaining freeway speeds when climbing hills!!!!
Any thoughts or suggestions would be greatly appreciated!