New Radiator Install

gvsho

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Just installed a new Mishimoto aluminum radiator with synthetic coolant. Install went well but now my 2000 TJ won’t get hotter than about 180 degrees according to the temp gauge on the dash so thermostat not opening up. Is the radiator THAT good or am I missing something? Just a little nervous. :)
 
The first mistake you made was installing a Mishimoto radiator.

They will make it run cooler, but contrary to popular belief, that’s not a good thing.

It’s possible your thermostat is stuck though.
 
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How? The thermostat will just stay closed longer until it reaches temp.

No, I just meant the overall idea of trying to make an engine run cooler is a silly one, as engines were designed to run within a certain operating temperature range.

There are people who will for no reason whatsoever (other than thinking it’s better) try to “upgrade” their cooling system in search of lower temps. That’s what I am getting at.
 
So my "thinking" was...if the engine just now isn't getting hot enough (>215 degrees), the thermostat won't open up and let the coolant circulate. Mine (it's 4.0L BTW) just doesn't seem to be getting hot enough even if I let it idle indefinitely. The temp gauge increases from cool gradually like you'd expect (so no gauge issue) but it tops at about 185-190 degrees then stabilizes.
 
So my "thinking" was...if the engine just now isn't getting hot enough (>215 degrees), the thermostat won't open up and let the coolant circulate. Mine (it's 4.0L BTW) just doesn't seem to be getting hot enough even if I let it idle indefinitely. The temp gauge increases from cool gradually like you'd expect (so no gauge issue) but it tops at about 185-190 degrees then stabilizes.

Wrong (backwards) thinking. The engine will get VERY VERY hot if the thermostat stays closed, so that isn't your problem. Replace your thermostat with this one:

https://www.amazon.com/dp/B000C7YRNM/?tag=wranglerorg-20
 
So you're saying the thermostat is staying open? Sorry, I'm not trying to be obtuse, just trying to understand. I didn't replace the thermostat but it was working before I swapped radiators.
 
So you're saying the thermostat is staying open? Sorry, I'm not trying to be obtuse, just trying to understand. I didn't replace the thermostat but it was working before I swapped radiators.

That's what I and other are saying. When an engine won't reach operating temp it means that the water is being cooled by the radiator and not being allowed to reach the operating temp that's controlled by the thermostat.
 
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It could also be the wrong thermostat. Many put 180* thermostats in thinking it's solves other radiator problems. Either way I would install the 195* thermostat that I referenced above.
 
*light bulb going off* I've got what you're saying at least, but here's the rub. BEFORE new radiator: engine heated up to operating temp, thermostat opened and temperature was reduced. This would happen just past the mid-point of the temp gauge which according to my eye would be around where it should I'd think. AFTER new radiator (and all else being equal - no changes): temp gauge only gets up to about 185 and stays there.
 
*light bulb going off* I've got what you're saying at least, but here's the rub. BEFORE new radiator: engine heated up to operating temp, thermostat opened and temperature was reduced. This would happen just past the mid-point of the temp gauge which according to my eye would be around where it should I'd think. AFTER new radiator (and all else being equal - no changes): temp gauge only gets up to about 185 and stays there.
It doesn't matter, replace the thermostat as recommended so many times above. 195 degree, non-failsafe. Don't get into analysis paralysis when you have a full chorus singing replace the thermostat. Get 'er done. :)
 
Just trying to get my small brain to understand, Jerry. Hate 'fixing' something without really understanding the why. I'll try that. Thanks!
 
Sometimes different types of coolants don't play well together. That may have caused your thermostat to stick open.
 
Sometimes different types of coolants don't play well together. That may have caused your thermostat to stick open.
Just to circle back on this post...I finally got a good day to take the actions suggested here by members and wanted to give a quick update. The symptom I was having was my engine temp was only getting up to about 170 and just staying there. The Jeep drove fine and engine sounded right, just wasn't heating up then cooling back down once it hit 195 or so. I replaced the thermostat (tested it in boiling water first to make sure it was good) and now the cooling is operating as expected. Just for laughs, took the old thermostat and also tested it. It seemed like it started in a closed state and it did open but noticed the round copper 'peg' in the middle was way off center and touching the inside of the metal ring that surrounds it. Not sure if that was an issue but it working now so something must've been wrong with it.

Thanks for everyone's help.