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closed system woes

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well anytime i do anything in 4wd or a lot of action in 2wd i over heat. driving around, sitting in traffic its okay but not the temps i was used to seeing before the pressure bottle blew and all that crap happened. anyway I'm sick of it and want to do the open system swap. ive looked at tons of threads but none really making sense to me. now I'm the kind of guy where seeing something makes more sense instead of the paragraphs ive been reading through. if anybody has pics, step by step please post them. i think i know what all i need to buy but if you've got part #s or anything. again please post them. thanks

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You first have to narrow down what you're asking. There can be a number of things that contribute to over heating an engine.


Air in system.


Clutch fan not spinning fan at proper speed or failed.


If you have a second cooling electric fan is it working?


Thermostat working?


Heater core plugged or heater valve working?


Water pump good?


Do you have adequate pressure on your system? Usually around 13-16lbs is what the cap is rated for. The pressurized system raises the boiling point on the antifreeze water combination so it won't turn into a gas and blow the cap off and thus overheating. That said it's best if you have someone pressure test your cap and the truck to see if you have any leaks. If you don't you might have air in the system. To eliminate the air from a closed loop system (After pressure checking for leaks) start the truck with the cap off the pressure bottle, the bottle should be half full. Squeeze the lower and upper radiator hoses slowly until all air bubbles get forced up into the pressure bottle. You will hear a gurggling sound and see the bubbles come up if yours is clear enough to see out of. After doing that for about 10-15 minutes all the air should be out of the system. You can reinstall the cap, one note is that you don't over tighten the cap and strip it out. Let the truck cool fully for an hour and recheck the coolant level and add as needed.


I hope this helps

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Hey I had the same problems with my 89 MJ when I first got it, the motor was knocking because it had been run hot. When I did a motor swap I just swapped in a new newer 90- Radiator. I already had the new 180 degree thermostat , I found a junk yard overflow tank and heater valve from a newer cherokee. I went with a new waterpump from the year motor I had. The Rad was a bolt in, the tank took about 3 feet of hose and a wire tie to mount . Also I saw that the freeze plugs were leaking which probally caused the whole problem , I switched them out with brass ones. It wasn't hard at all.

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