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Overheating issue

9K views 18 replies 11 participants last post by  Cjnelson5211 
#1 ·
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 head gasket since it never gets hot any other time. Thanks for your help.
 
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#5 ·
A bit more detail please.

How long are you holding it at 5000 RPMs? Altitude above sea level? Air temps when it does this? Does it “overheat” under normal driving conditions at RPMs below 3500?

240 - 250 degrees is not uncommon for a JK held at high RPMs for an extended period. Especially if you’re at higher altitude climbing a hill.
 
#6 ·
I live in Sheridan Wyoming, about 3500ft. Air temps could be 10-55 deg. Never overheats any other time only at 5k rpm going 75 up a grade Or going 50+ up Into the mountains. Usually held 5k rpms for 30secs or so.
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
 
#9 ·
I have determined the thermostat in our Jeep JKs is too small and never opens far enough. Secondary Temp gauges make us watch closely making us aware of temps all the time then we start tripping.
I fixed my JK by drilling 3- 3/16" holes in the thermostat mounting surface This does 2 things it burps locked air and increase flow. You will throw a code if you don't let your rig warmup for 5 minutes in the winter. A
3.6 At high rpm can not pass enough fluid through the tiny half opened thermostat.
I did reset fan to come on low above 190 medium 200 high 220. No more over heating for me.
Oh and no JK is safe to drive above 65 mph.
 
#13 ·
If you change the thermostat again, suggest you go with OEM. I understand (but can’t personally verify) that some aftermarket JK thermostats do not always open fully and tend to restrict flow.

You have a Jeep that doesn’t overheat under any typical driving conditions so your problem is more of an outlier. The engine, under highest load only, is generating more heat than the cooling system can get rid of. Check thermostat, make sure the radiator surface is clean with no aerodynamic obstructions, confirm no air in the cooling system.

Include a picture of the front end with your winch.
 
#14 ·
Used HP tuners for fan setting.
Thermo. Remove the thermo from plastic neck.
Outside the bulb you see 1/2" wide surface creating a circle that mounts the thermo.
In that outside edge I drill 3 holes.
For years old mechanics would drill one small hole just to prevent air lock. I drilled 3.
 
#15 ·
Here’s the thing my friend if your Jeep drives good on the freeway fine and everywhere else I say your doing alright and you have nicely built Jeep as long as it doesn’t overheat anywhere else I believe you are fine a lot of trucks carrying a load up a grade overheat as well just take it slower up the grade turn off the A/C get in the truck lane and find a happy speed. And even then you may still over heat turn the heater on as long as when you get to the top and start coming down the grade the engine cools off and it doesn’t continue to rise I think you’ll be alright.
I have a 30 year old xj that does pretty much the same thing and I’m running 33s and I’m trailering a rzr and it overheats I just turn off the ac turn on the heater and go about 55-60 up the grade and take my time usually when I get to the top it cools off.
 
#18 ·
Here’s the thing my friend if your Jeep drives good on the freeway fine and everywhere else I say your doing alright and you have nicely built Jeep as long as it doesn’t overheat anywhere else I believe you are fine a lot of trucks carrying a load up a grade overheat as well just take it slower up the grade turn off the A/C get in the truck lane and find a happy speed. And even then you may still over heat turn the heater on as long as when you get to the top and start coming down the grade the engine cools off and it doesn’t continue to rise I think you’ll be alright.
I have a 30 year old xj that does pretty much the same thing and I’m running 33s and I’m trailering a rzr and it overheats I just turn off the ac turn on the heater and go about 55-60 up the grade and take my time usually when I get to the top it cools off.
My JKU 2012 does the same as OP.
I removed my protective grill between slots to get more air flow.
I have winch, PSC power steering cooler, tranny cooler, AC condenser all in front of rad. It’s no wonder it heats up going up big hills under load.
I’m thinking changing my power steering cooler to smaller one in future.
Around town though no issues but up steep inclines it creeps up toward 3/4 but never reaches it. I usually will turn heat up, temp drops back normal and I only go around 60mph, never 75.
My 488 gears help so still in 5 gear not dropping to 4 or 3.
Been like this couple of years now.
I also take front end apart and clean all mud out between rad and coolers also to make sure good air flow.
I also replaced thermostat with OEM one and rad cap.
I use to worry but now just make sure no leaks rad and overflow have correct amount of coolant in it.

These motors run hot just keep eye on it.

Grill in


Grill removed


Sent from my iPad using Tapatalk
 
#19 ·
Try this I know you may not like this but this is what I did temporarily until I find a good solution I’m thinking of making handles so I can carry my winch better and then just plop it back on when I go on a trail and screw in the bolts. Atm I don’t mind doing that. now here in south California summer it gets HOT some days we are reaching 100 I took the winch off my yj because it blocks the radiator and I did this during the cooler months I didn’t over heat once my Jeep stays under 210 rn because I’ve changed everything out in my cooling system so I’m sitting at about 195 on highways it jumps alittle if I have A/c on tho it will go over and in the summer months it does go over so I tend to keep my a/c off sometimes going up grades yes I’ll over heat during the summer and I’m not too worried I just take it slow stay 60 no need to push it. (pretty sure the compressor is just old it runs and gets cold it’s just 33 years old) my Jeep also has 4 inch lift and 1 inch boom shackles with 33 inch tires. I also have stock gears and no hood vents(I know I know shut up it’s my next upgrade) what I’ve seen with a lot of the newer jeeps is they are able to drop there winches lower than the grill woth these different bumpers which is pretty smart I know it’s probably to late but if you have a way to drop your winch lower or get a different bumper which I know is expensive it may help but test my theory out first before you got spend a paycheck.
 

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