Yet Another Overheating MJ
06-04-2015, 06:02 PM
#16
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Year: 1996
Model: Cherokee (XJ)
Engine: 4.Slow
Yet Another Overheating MJ
Cruiser, heres a wild thought to ponder. Now the radiator cap is designed as a pressure relief, opening when coolant gets too hot, creating pressure. Now from what I've noticed on Xjs, as I've had nothing but closed systems, that screw on lid to the pressure tank has an o ring and valve inside the cap that acts like a radiator cap. Do you think it would be a wise move to fully convert to one or another system to better help diagnose the problem?
06-05-2015, 03:20 PM
#17
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Year: 1989
Model: Cherokee
Engine: 4.0L I6
Update:
Didn't have class today so I replaced the thermostat with an OEM 195 degree Mopar one. Pulled the old one out (180 degree t-stat by the way
). I put it in boiling water and it opened. Threw the new one, started it up and the MJ climbed to around 230 but then back down to around 200 and stayed there! But of course, it went right back up to 230+ and then I got angry/sad lol. Might try burping it again after it cools down.
Didn't have class today so I replaced the thermostat with an OEM 195 degree Mopar one. Pulled the old one out (180 degree t-stat by the way
). I put it in boiling water and it opened. Threw the new one, started it up and the MJ climbed to around 230 but then back down to around 200 and stayed there! But of course, it went right back up to 230+ and then I got angry/sad lol. Might try burping it again after it cools down.Consider, also, disc your lower and upper rad hose and try flushing your rad. Since you have the cap in the system it is now effectively an "open" system. Pick up some late model XJ upper heater hoses, and a universal tank from your local parts store. Ditch the heater valve and turtle tank.
06-05-2015, 06:19 PM
#18
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Year: 1990
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Cruiser, heres a wild thought to ponder. Now the radiator cap is designed as a pressure relief, opening when coolant gets too hot, creating pressure. Now from what I've noticed on Xjs, as I've had nothing but closed systems, that screw on lid to the pressure tank has an o ring and valve inside the cap that acts like a radiator cap. Do you think it would be a wise move to fully convert to one or another system to better help diagnose the problem?
06-06-2015, 05:38 PM
#19
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Year: 1999
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Engine: 4.0 Inline 6
Got some heater hose and deleted the heater control valve. Got a bottle out of a 97+ xj. Had to go to work so I didn't test it out yet but will update once I get off work.
06-07-2015, 02:13 PM
#20
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:-)
Here's what I ended up with. It's not pretty but it works! There are tiny bubbles going into the tank but i'm hoping its just air that is escaping out of the system. Drove around my neighborhood and the gauge read 210 and never went over. Thanks for all your help and suggestions guys! 
06-07-2015, 03:38 PM
#22
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Year: 1999
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I'm praying that's not the case! I'll probably go to a shop and have them do a compression test just in case.
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