swilson Posted October 15, 2007 Share Posted October 15, 2007 Guys: This is the story. I have an 89 comanche 4.0L 2wd auto with air. I got the truck last winter. It had no heat when i got it so i back flushed the heater core and that fixed that. Then in the spring when i was towing my boat on the highway the coolant bottle started boiling over. The temperature idiot light did not come on! The motor got very hot, but no major damage. The next day i put in a new thermostat and flushed out the rad with a garden hose and checked to make sure all lines were clear, as well as checking that the pump was working fine. I also installed a secondary temperature guage. I removed the sender that is behind the front motor mount on the drivers side to install the new guage sender. My engine temp has been between 200-260 deg. (when the outside temp is 30 deg). I have since changed the thermostat again and done a home bottle rad flush. My temps are still the same. Even if i run the aux fan full time it still gets hot. Yesterday while driving in Toronto, the temp idiot light came on at around 200 deg. It has never come on ever before....ever. I thought that i had taken out the sender. This is my delema. Did i take out the wrong sender? Is there another? What can i do to get my temps back down to where they belong??? Help!! P.S. - The rad looks to be in good condition. Few bugs but thats all. Link to comment Share on other sites More sharing options...
90PioSport99 Posted October 15, 2007 Share Posted October 15, 2007 Guys: This is the story. I have an 89 comanche 4.0L 2wd auto with air. I got the truck last winter. It had no heat when i got it so i back flushed the heater core and that fixed that. Then in the spring when i was towing my boat on the highway the coolant bottle started boiling over. The temperature idiot light did not come on! The motor got very hot, but no major damage. The next day i put in a new thermostat and flushed out the rad with a garden hose and checked to make sure all lines were clear, as well as checking that the pump was working fine. I also installed a secondary temperature guage. I removed the sender that is behind the front motor mount on the drivers side to install the new guage sender. My engine temp has been between 200-260 deg. (when the outside temp is 30 deg). I have since changed the thermostat again and done a home bottle rad flush. My temps are still the same. Even if i run the aux fan full time it still gets hot. Yesterday while driving in Toronto, the temp idiot light came on at around 200 deg. It has never come on ever before....ever. I thought that i had taken out the sender. This is my delema. Did i take out the wrong sender? Is there another? What can i do to get my temps back down to where they belong??? Help!! P.S. - The rad looks to be in good condition. Few bugs but thats all. The sending unit that controls your idiot light is a brass fitting in the back of the head on the driver's side. It takes a deep 13mm socket on about a 12" extension to get it. If you can, dig up a sending unit and a full gauge cluster from a higher optioned XJ, that way you actually have some clue as to what is going on. It would drive me nuts relying on idiot lights. As far as the overheating issue, try to bleed the closed system. If bleeding the closed system doesn't work, and you've replaced everything else, I'd consider going to the open system. Hope this helps. -Collin Link to comment Share on other sites More sharing options...
Rob S Posted October 15, 2007 Share Posted October 15, 2007 It is a closed pressurized system. Is the coolent bottle and cap in good condition? When it gets warm, turn the cap a little to loosen it, if you hear the air hissing, the system is pressurized. If no hissing, then either the cap or coolent bottle is bad. Hope that helps. Link to comment Share on other sites More sharing options...
swilson Posted October 15, 2007 Author Share Posted October 15, 2007 The system is completely free of air and the bottle and cap are good and hold pressure. If the idiot light sender is on the back of the head, then what was the sender that i removed behind the motor mount on drvers side? Link to comment Share on other sites More sharing options...
90PioSport99 Posted October 15, 2007 Share Posted October 15, 2007 The system is completely free of air and the bottle and cap are good and hold pressure. If the idiot light sender is on the back of the head, then what was the sender that i removed behind the motor mount on drvers side? That is actually the Coolant Temperature Sensor which feeds information to the computer. It is a completely separate entity from the gauge/light sender. Link to comment Share on other sites More sharing options...
swilson Posted October 17, 2007 Author Share Posted October 17, 2007 fixed i think. new rad. old one did not look bad but the rad shop said it was f*&k'd Link to comment Share on other sites More sharing options...
Oizarod115 Posted October 17, 2007 Share Posted October 17, 2007 fixed i think. new rad. old one did not look bad but the rad shop said it was f*&k'd that happened to me... i threw parts at it for a long time. nothin helped, new 3-core modine rad. and VIOLA! 180 all the time :chillin: Link to comment Share on other sites More sharing options...
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