Welcome to the world of Jeep emisions, they like to run the engine hot.

Try leaving the AC on it will turn the engine fan on Low and keep coolant temps down

The 35's and 3.73 is putting a strain on the motor too making it work harder to keep up to speed

 

Those temps are normal in my experience. The ECU seems to be programmed to let the engine run in that range since the radiator fan duty cycle on surface streets is only around 10-15% at 220F. If the engine were actually overheating then the fan speed would increase, but since it doesn't that demonstrates that the ECU is happy with the temperature.

I have noticed that when in 4WD low range the fan speed does increase at lower temperatures and coolant temp is held to around 200F or so no matter what I do (further demonstrating that there is no problem with actual cooling capacity), but get back on pavement and return to 2WD street config and temp runs around 220F. That is just where the engineers seem to have set it for normal street driving. Maybe partially for emissions, or maybe to increase mileage because the engine runs more efficiently at higher temperatures, plus the fan is a big HP draw so running it unnecessarily also uses fuel. But whatever, there is no problem with it as long as your cooling system is in good shape.

 

We seem to be having the same problem with GameChanger lift & 35’s but we haven’t re-geared. It seemed to start around the time we increased the tire size but started overheating & we lost AC on a long road trip of 6 hrs at 104 degrees outside. Radiator replaced, thermostat replaced, AC condenser & evaporator core replaced on a 2014 Jeep 😡. On the coolant temp sensor on the dash it will still run up to 245 on a hot day (like 102-104 degrees in texas). Normal op temp is 190-220 supposedly. They want to replace the thermostat for the 3rd time in 3 years… coolant was replaced w/ radiator 2 years ago. If that doesn’t fix it or putting in a lower temp thermostat (?), they are going to chalk it up to 35” tires. ?? Seems very odd to me because Just about everyone I know has 35-37s and hasn’t complained about this issue. ?? Thoughts?

 

A lower temp thermostat isn't going to do much. The stock one opens at roughly 203 and STAYS open so long as it is above that temp and of course you are overshooting that 203 by a long shot, so having one which opens a little earlier won't do a lot.

I see someone referenced "3.73" gears, and maybe I am blind, but I don't see YOU stating which gear size you have. Do you have 3.73 gears... or perhaps 3.21 gears... because 3.21's with 35's in the Texas heat would be pretty hard on the jeep.

 

Welcome to the forum. Hard to imagine that your radiator, and the condenser, and the evaporator (seriously?) were all bad at the same time, but anyway...

3.73 is somewhat high gearing for 35's but it's not enough to cause the problem you describe. As above up to 225 can be considered normal in the JK, but 245 is too hot. Is that from an accurate source? (meaning a scanner or the digital display on the dash info center, do not trust the 'analog' dash gauge for much.) If it really is 245 and you've recently had the radiator and thermostat replaced (and replacing it a third time hints of throwing parts at it rather than really diagnosing) then one of the most common causes is simply air trapped in the cooling system. Actually not so simple because it can be tricky to purge the system properly and even many pro shops fail at this.

There are tutorials online but basically if you want it done right you need to fill the heater core manually then purge through the thermostat air bleed while using a funnel at the radiator. It can take some extra time and shops don't like that, but it's the only way to ensure that all air has been bled out of the system. If this doesn't cure it then you can diagnose further, but its definitely the first step from where you are.

 

Thank you--this is very helpful! Well... in July 2020 the 1st time it overheated on a 6-hr road trip/lost AC at the same time (gauge on dash was far right/steaming radiator - hot; no water in radiator overflow), they found a radiator leak, replaced radiator, thermostat replaced, and added freon to the AC and put dye in it. Supposedly never found a leak in the AC but adding freon isn't usually needed on a 6yo car at the time without a further problem. It was making weird noises through the AC at the time, gauge on dash was still running about 3/4 (between middle/hot) even running 75mph for 10-15min, so the thermostat was replaced again when brought back. Checked for AC leak & found none, despite noises in AC unit that were new. Couldn't figure out why it was running hotter than normal....finally gave up and brought it back in July 2021 when AC was working less than stellar and making noise - evaporator core replaced as a leak was found there; thermostat replaced again. They blamed the higher running temp on bigger 35" tires that were put on late 2019. Oddly, never noticed any issue until July 2020 on a long road trip with tires affecting anything. Still AC was making noise throughout the next year, still running hot and went on a 6-hr road trip again and again lost AC completely on the trip and again it was running 3/4 hot on the gauge but didn't overheat. Took it back again in June 2022--the mystery noise we'd been hearing for 2 solid years was the AC compressor (it's finally gone now); no water in the radiator overflow yet again but running 3/4 on the gauge was blamed on 35" tires. Although this time, they clicked the digital display over to the coolant temperature, which I'd never seen before (I had no idea there was a sensor there) -- pulled out of the parking lot with a cold engine -- coolant was 190 degrees....it took 1/2 mile for it to get 225 and by about 2 miles down the road, it was 245 degrees when I sped up to 70mph. It was 104 degrees outside... So the AC probably was broken in 2020. Who knows on the radiator to be honest. I guess since a leak was found & overheating it was bad. I doubt that many thermostats were bad. The remaining problem is that the coolant temp is just running too hot. They said the coolant was full and did not detect a leak but we had just put water in the overflow because it was dry & running hot. Complicated.... I just can't accept that 35" tires would make the coolant run that hot within a short period of time. And to run so hot--up to 245. We only take it on a road trip once a year or less but both road trips have been disasterous --nothing like 100-105 degree Texas weather outside when your car starts overheating and you have a non-AC ride 3-4 hours back home 2 road trips in a row! Hope this helps explain and i greatly appreciate the troubleshooting steps above!! ^^.

 

I say 220-225 seems about right, so I wouldn't waste the money on flushing unless you just want peace of mind. I'm on 37's and 5.13 gears and my temp runs between 217-231 day or night here in Hawaii with mix city and highway. My commute is mostly hills everyday so its stays on the lowered of the 217-222 when I'm not heading to work.

 

I'm leaving on a road trip tomorrow and I'll try to pay closer attention to coolant temps but I'm pretty sure every time I've checked in the past I was only in the low 200's at most.

3.73, 6-spd, 2.5" lift, 32" KO2's

 

80°F ambient, ~2.5 hours and over 100 miles so far, I checked temps at a steady 70 mph they varied only slightly 194-202°F.

 

I rarely see temps above 210 with the AFE Bladerunner gt radiator. But I am fairly close to sea level and don’t have an auto transmission

 

2015 stock JKUR. Temps normally at 200. Yesterday I went on a road trip with some descent hills on a 104 degree day and temp climbed to 220 but then dropped back down as soon As I would reach the top.

I thought I saw somewhere that having worn out cam phasers could cause the engine to run hot but I could be mistaken.

 

220 is in the range of "Normal". Your fan doesn't even kick into high gear until about 226

 

I’m having the same issue. Got the over temp light - turns out it was a radiator leak. Replaced radiator, water pump, ps pump, thermostat and oil cooler. Bled/burped radiator to make sure no air bubbles. In Baton Rouge ambient (90-95F) it will creep up to 250 running 80 in the interstate. Once I slow down or hit traffic, it will drop to 230s/240s. Sitting idle in the driveway, maintains 220-224. Running 35s, 3.5” lift, stock 3.21 gears, aftermarket bumper and angry grill. Never had any temp issues until I went from 33s to 35s and added the lift. Hard to believe those 2” make that much of a difference. Thoughts?

 

 

The lift and tires do make a big difference. You are losing gearing advantage with the bigger tires and you are exposing more of the rig to drag, particularly at speed with the lift. Most will say 3.21 was already low for the stock size tires and going to 35, you will want to change your axle gears to regain mechanical advantage and put less strain on your motor. The lift adding drag you aren't going to do much about. Combine that with at least the little bit of airflow you cut into with the grill and bumper (not as bad as others, certainly) and I think you likely just reached the limits of your cooling system after adding up a bunch of small things that on their own, it would handle.

One point to make on burping the 3.6, make sure you use the relief valve on top of the thermostat housing when burping the system. It's pretty much required to get all the air out, you will be surprised.

 

The lift and tires do make a big difference. You are losing gearing advantage with the bigger tires and you are exposing more of the rig to drag, particularly at speed with the lift. Most will say 3.21 was already low for the stock size tires and going to 35, you will want to change your axle gears to regain mechanical advantage and put less strain on your motor. The lift adding drag you aren't going to do much about. Combine that with at least the little bit of airflow you cut into with the grill and bumper (not as bad as others, certainly) and I think you likely just reached the limits of your cooling system after adding up a bunch of small things that on their own, it would handle.

One point to make on burping the 3.6, make sure you use the relief valve on top of the thermostat housing when burping the system. It's pretty much required to get all the air out, you will be surprised.

Thanks you for the nice tip

 

@DiamondMox ; thanks for the education on the radiator bleed. I’ll verify no air bubbles.


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Anyone have any thoughts for what gears for 35’s in a daily driver?


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Much debate, but you can start by looking at the chart.

 

Running 35's with 3.21 gears pretty much mean your engine load is running at near 100% all the time. It is going to run hotter.