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2015 Jeep Wrangler Overheating Issue

appst8design

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Jun 14, 2022
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First time posting to this forum but I'm at my wits end trying to diagnose an overheating issue. I've got a 3.6 JK Altitude Wrangler with 77k miles that's barfing coolant out of the radiator overflow tank. So far I've changed the coolant temperature sensor (I was getting a code, it's gone now), thermostat and radiator cap each time refilling and burping the system on a very inclined hill. I've had a leak down test performed by a mechanic and ruled out a cracked head gasket (no coolant in oil or oil in coolant). Runs great other than it overheats after it pushes all the coolant out of the system. I've also read that it's a pain the a** to get the air out of these engines but at this point with all the burping an refills I'd think this wouldn't be the case. Typically will go for a couple days after a refill leaking slightly out of the overflow before really discharging larger amounts (I assume this is because the more coolant it loses the faster it warms up and more it boils over).

Anyone have any suggestions? I was thinking maybe clogged radiator or bad water pump (I was under the impression when pumps fail it's all or nothing)? Wanted to ask before just throwing money at it.
 
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appst8design

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Is the cooling fan working correctly?

Anything blocking the cooling of the radiator?
Coolant fan comes on when ECT reads 220ish (guessing at this with OBD reader) sounds like Jeep is about to take off.

Nothing blocking front of Jeep, fins look in good condition.
 
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appst8design

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Did you use the correct coolant? If you mix coolant it will crystallize and form a goo and plug up.
I did accidentally mix different coolants awhile back but had radiator flushed day after. You think the symptoms above could be signs of a plugged or partially blocked radiator? That's one reason I was kind of leaning towards getting that replaced next.
 

mrjp

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I did accidentally mix different coolants awhile back but had radiator flushed day after. You think the symptoms above could be signs of a plugged or partially blocked radiator? That's one reason I was kind of leaning towards getting that replaced next.
Yea I would have the radiator rodded out and flush the block and heater core.
 

Dirty Dog

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Last log in was June 15.
He's in the wind . Quite a few seem
to join to get help . Get free advice than
bam. Gone . It's kinda a drag as issues such as
this, would be good to know how or if was resolved .
Maybe we're all giving stupid advice. If that's so, I don't wanna know!
 

Kevyluv

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Oct 3, 2022
Messages
11
Location
Oklahoma
I had the same issue. Dropped a new radiator and new engine after it failed a block test. Two thermostats went on the old engine with no relief. Overheating continued with new engine and took it back to the mechanic in which he scratched his head and said he didn’t know what could be causing it. I was fed up with it last night and bought a third thermostat but first one for the new engine after a long drive and having to pull off the highway twice to cool down. Burped the system with no success and the replaced the thermostat and bled the system of air this morning and the temps never reached 225 degrees while running highway speeds and A/C blowing. I’d say on average the running temperature was around 215 all day. I guess I have bad luck with thermostats…lol! I’m just glad to get it fixed.
 

Flipflop

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Sep 12, 2022
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Kentucky
I had the same issue. Dropped a new radiator and new engine after it failed a block test. Two thermostats went on the old engine with no relief. Overheating continued with new engine and took it back to the mechanic in which he scratched his head and said he didn’t know what could be causing it. I was fed up with it last night and bought a third thermostat but first one for the new engine after a long drive and having to pull off the highway twice to cool down. Burped the system with no success and the replaced the thermostat and bled the system of air this morning and the temps never reached 225 degrees while running highway speeds and A/C blowing. I’d say on average the running temperature was around 215 all day. I guess I have bad luck with thermostats…lol! I’m just glad to get it fixed.
I’m about to just trade off .. I’m so over it.
 

Kevyluv

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Oct 3, 2022
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11
Location
Oklahoma
I’m about to just trade off .. I’m so over it.
Try bleeding the air out of the system and watch for when your thermostat opens up. The top radiator hose will get hot when it does. It should open at 203 degrees. If it doesn’t and opens up at a higher temp or doesn’t open at all then you’ll know the thermostat needs to be replaced. I went off of my digital reading on my dash. It’s a cheap part and easy fix.
 

Anybodyhome

USN Retired (1973-1993)
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Jun 15, 2020
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Nashville, NC
Try bleeding the air out of the system and watch for when your thermostat opens up. The top radiator hose will get hot when it does. It should open at 203 degrees. If it doesn’t and opens up at a higher temp or doesn’t open at all then you’ll know the thermostat needs to be replaced. I went off of my digital reading on my dash. It’s a cheap part and easy fix.
Best way to do this is with JScan.
When I had my issue a couple years ago, which I posted extensively about, the final test was the thermostat open temp. Had the app open on my phone while my JKU was running and I put a slight grip on the upper radiator hose. You can definitely easily feel when the t-stat opens while watching the live data temp on the phone. Just don't hold onto the hose too long.