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'93 Sundance 2.2L Temp Fluctuation - Stumped!

14K views 37 replies 7 participants last post by  John Wood 
You need to get a coolant system pressure tester and test the cap and the system. You may have a small leak somewhere slowing it to suck new air into the system.
 
When my old Dakota had a weak hose clamp and it sucked air and the temp would climb (especially at idle) then drop down after it spiked up. I found out by revving the engine that the temp would usually drop quicker. I suspect the reason was because the faster spinning water pump moved the coolant faster and created a bit more vacuum to seal the leaking hose connection just a bit rather than sucking air. I finally put a pressure gauge on it after a week or so of this and found the weak hose clamp on the lower radiator hose. Fixed that and the gauge never spiked again and temps stayed close to normal at all times.

Buy, borrow or rent a coolant system pressure tester and see what happens. Your symptoms sound exactly like a car that is ingesting air into the coolant system.
 
I've said it before, but if you've got a bleed hole in the thermostat already and this keeps happening you are probably getting NEW air into the system. You've got to find and fix that.
 
adsjds said:
But wouldn't that spot leak as well? I've been over every inch of this engine and firewall....there are no leaks and the hoses and the radiator have been replaced. I guess a pressure test wouldn't hurt. Thanks.
I have had a leak that sucked air but never put a drop of coolant on the ground. it can happen.
 
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