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Jeep jk Overheating issue

BlaZeus

BlaZeus

The Real Mateo
Joined
Jan 28, 2015
Posts
628
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Location
Sheridan, WY
Hey guys, I have a 13 jku rubicon with 135k miles, 4” lift on 37’s, winch, etc. been fighting an overheating issue for a few months now. Only overheats on high load on the freeway so going up a grade and going 75+ mph. Or going up a winding steep grade going 45+. Temps will creep all the way up to 250 in some instances. It never gets above normal operating temps while idling or when driving around town or when driving on flat freeway. I have been running 37’s with 3.73 gearing for about 1.5 years now. I think It started around 7 months ago or so around when I went from 37/12.5/17 general grabbers to 37/13.5/17 nitto extreme terrains with a lot more tread. I had replaced my t stat about 2 months before that. When I was driving up the mountain one day I noticed my temps started to rise and I could smell coolant smell. Went home and found my water pump had dried coolant around it. Had a friend come over and check it out and he found my radiator also had a small leak. I replaced the radiator and water pump and it was still overheating under high load. I put a vented hood on it and that didn’t help. I replaced the t stat again and new radiator cap and thought that had fixed it, nope. So then I figured it had to be the gearing was causing the engine to work too hard. So I just finished a gear swap to 4.88’s and I drive it on the freeway last night and hit a grade and it started to overheat again while going 75 and at like 5k rpms. I’m at the end of my rope with trying to figure out what it could be. Any body have any ideas? Could it be tires? I didn’t think it could be a head gasket since it never gets hot any other time. Thanks for your help.
 
Anything in front of the radiator like a winch, cosmetic grill, etc?

Honestly, I’m not surprised it might overheat during sustained 5k rpm driving. That just not where it’s designed to operate most efficiently.
 
Can you borrow some other tires? Something smaller or more all terrain? Then give it a good drive?
Other than that, maybe something in the radiator or an old suction hose collapsing.
 
nvrenuf said:
Anything in front of the radiator like a winch, cosmetic grill, etc?

Honestly, I’m not surprised it might overheat during sustained 5k rpm driving. That just not where it’s designed to operate most efficiently.
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I do have a winch in front and the condenser and oil cooler are in front of the radiator from stock.
 
K85 Octane said:
Can you borrow some other tires? Something smaller or more all terrain? Then give it a good drive?
Other than that, maybe something in the radiator or an old suction hose collapsing.
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That was going to be my next step. Put the old tires back on and see. I also replaced all the hoses when I did the water pump and radiator.
 
If the winch is big enough to obstruct air flow you might consider taking it off for a test drive.
 
do a block check, you may have a small crack in a head that only opens to let combustion gas into cooling system when working hard. Have found this on a couple of occasions with those sysmtoms
 
Wes Harden said:
do a block check, you may have a small crack in a head that only opens to let combustion gas into cooling system when working hard. Have found this on a couple of occasions with those sysmtoms
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Agree but you'll typically see coolant coming out of the reservoir bottle or find the hoses compressed with gases. So....check the bottle level and your hoses while the truck is running, best time is an hour after driving. You'll see the hoses still tight because combustion gases are trapped inside. When my old engine was doing this, I'd find compression in the system a day or two later.
 
K85 Octane said:
Agree but you'll typically see coolant coming out of the reservoir bottle or find the hoses compressed with gases. So....check the bottle level and your hoses while the truck is running, best time is an hour after driving. You'll see the hoses still tight because combustion gases are trapped inside. When my old engine was doing this, I'd find compression in the system a day or two later.
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Yeah, checked the coolant reservoir leak tube last night after I got home and it was dry. I’ll check the hoses.
 
Babaganoosh said:
Ls swap it.



Honestly this is weird but I applaud you for driving at 5k rpm for time, anything will get hot.
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That's what I was going to say.
You go from undergeared to driving at 5000 rpm, in either case I would expect overheating.
Now since you have been driving it before and it seemed fine and suddenly it started overheating I suspect a head or gasket problem, it's what happened to me a few times. I had it checked, confirmed then just used blue devil
 
imiceman44 said:
That's what I was going to say.
You go from undergeared to driving at 5000 rpm, in either case I would expect overheating.
Now since you have been driving it before and it seemed fine and suddenly it started overheating I suspect a head or gasket problem, it's what happened to me a few times. I had it checked, confirmed then just used blue devil
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Found That there was coolant running down the back of the block and bell housing after pressurizing the system so was able to see where the leak is coming from, there is an oil cooler filter located underneath the intake. Replaced that and now no more leak, but still overheating at 5k rpm going 75 mph up a grade on the freeway.... I’m stumped
 
BlaZeus said:
Found That there was coolant running down the back of the block and bell housing after pressurizing the system so was able to see where the leak is coming from, there is an oil cooler filter located underneath the intake. Replaced that and now no more leak, but still overheating at 5k rpm going 75 mph up a grade on the freeway.... I’m stumped
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5k is way too much for sustainable driving.
I was overheating at 3500 in my k5, so I put a 700r4 in the place of th350 and dropped my rpms and no more overheating
 
I don’t get where the 5k rpm is coming from, are you sure that’s an accurate number? 4.88’s + 37’s + overdrive should be around 3k on the high side.
 
nvrenuf said:
I don’t get where the 5k rpm is coming from, are you sure that’s an accurate number? 4.88’s + 37’s + overdrive should be around 3k on the high side.
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He said pulling uphill which means he probably is in 3rd
 
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