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I wish I could find a jk in my area that didn’t overheat. I would like to see what they are doing different. Every 3.6 jk I have been in, that is a half dozen, has seen 235-245 temps off road or on long uphills. Then on here people say that theirs doesn’t. I am around 3 jkurs in hunting season every year, so not during high temp times. Every one of them the temp needle starts to climb in 4lo driving into a back country spot And every one of them I can hear the fan kick on when we stop to glass an area and leave it running. So that is 226 just sitting still at an air temp in the 40’s. My fan turns on in stop a go traffic when it is single digits temp out side. Gauge doesn’t budge until 235. So if you see anything other than dead nuts center you are 10 degrees from a warning. I would be surprised if everyone says they haven’t needle seen the needle go past center. To me 235-240 is overheating. Any time the fan is over come in cooling capability and you have to alter what you are doing that is overheating. Maybe what others are saying is limp mode or a CEL indicates over heating and that is the difference.
With all due respect here are several points in this post that represent misunderstandings, and that may explain some of the 'overheating' concerns. I'm not trying to pick on anyone, just using this as an example of some of the misconceptions.

For whatever reason the engineers designated that the fan not come on until 220 degrees or so, not sure why but really it isn't a problem. People tend to freak out whenever coolant temps exceed the thermostat setting by any amount but there really isn't any cause for concern for this as long system is operating as designed. No doubt that they could have calibrated the fan to come on screaming as soon as the coolant temp hit 195 but they didn't, probably because there is no need to. A large electric fan draws a lot of power and it could be that they simply didn't want the fan running and wasting power when it isn't necessary. For example, it is not overheating if you park an idling JK and the coolant temperature rises... it naturally will since there is no airflow until the fan eventually comes on. This is not overheating. And it doesn't matter if 235 is overheating 'to you', what matters is whether it is a problem for the engine. You will not lose coolant due to boiling until about 260 degrees, so if the engine doesn't care (and clearly the engineers are not concerned about it since that is the way the system is designed) then you don't need to, unless it impacts operation of the vehicle.

I think for the purposes of this thread we should define overheating as an event that actually affects operation of the vehicle, not simply a reading that one doesn't like or that your fan turned on. And if your vehicle is actually overheating to the point that operation of the vehicle is restricted every time you go out then something is wrong.
 

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^^^ Agree totally with you smiller1 ^^^^
 
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@smiller1 there are a couple of people commenting in this thread that have altered the programming to have the fan turn on earlier and it still goes into the 240s. If your definition of overheating is getting so hot it impacts the vehicle I am glad I am never going to buy a vehicle from you. My definition of overheating is when the vehicle has reached a point where there is nothing the vehicle can do to cool itself down during relatively normal operating conditions.

The is a couple misstatements in your post. Thermostat opens at 203, fan turns on at 226.

I don’t care if the fan turns on. What I care is when the temp passes 235, the fan is now full on and cannot cool the coolant down. So at that point you are overheating, you now have to intervene to cool the engine. Because if you continue you will go into limp mode in a few more degrees. So in your definition I never “overheat” I am not going to hit 245 and have the engine forced to protect itself from damage.
 

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My definition of overheating is when the vehicle has reached a point where there is nothing the vehicle can do to cool itself down during relatively normal operating conditions.
If you want to tweak that just a bit to say 'overheating is when the vehicle has reached a point where the vehicle cannot maintain a temperature within the design operating range during normal operating conditions' then yeah, I'd agree with that. And if that is happening regularly to a JK or any vehicle, you need to be looking for the problem.
 

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first and foremost , the hotter a engine get the less efficient it becomes.

also engine components get heat soaked,its not good for rubber or the plastics that are found in pentastars.

another overlooked side effect of hot coolant temps is the engine coolant also cools the motor oil and trans fluid.
if you want to take the time to watch the EVIC you can see corresponding fluctuations of oil pressure and engine temp and trans temps

in other words , the hotter you run the lower your static oil pressure
 
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If grill inserts are such a big problem why did engineers but one on the JT? Considering the cooling system is the limiting factor in towing capacity. Here's an article about the engineering of the JT cooling system that may provide some insight. From my experience with my JKU the grill insert didn't seem to make any significant difference.



https://apple.news/A25uvUeFXSWKCAJNtRkGLfA



I removed mine about 2 years ago. No difference. It also used to do this back when I did have an air dam still. I don't think either were the cause at least in my case.
 

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If you want to tweak that just a bit to say 'overheating is when the vehicle has reached a point where the vehicle cannot maintain a temperature within the design operating range during normal operating conditions' then yeah, I'd agree with that. And if that is happening regularly to a JK or any vehicle, you need to be looking for the problem.
My jk would go into limp mode if I let it. Does that qualify in your definition? I have watched it keep climbing on the eivc. Only thing stopping that from happening is me.

Lot of credit is given to engineers on this forum. The jk runs hot by design, yes, for fuel economy, period. The unplanned result is since it gets to designed operating temps so quickly for fuel economy it goes past that range too often and too easily. I definitely believe that the engineers designed the range to be 195-235 since that is where the temp gauge stays on center(which is ridiculous, to have a gauge where the next half is then only 10-15 degrees). But it flies past 235 too easily.
 

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It's not uncommon for manufacturers to make analog temperature gauges purposely nonlinear, so that owners do not bring the vehicle in because they think it's overheating when it isn't. I don't like that they're dumbed-down either but I can understand why they have to do it.

Regarding flying past 235 and going into limp mode, no, that's not normal and if it's doing that all the time then I don't know what to tell you other than I think something is wrong. I don't think I have ever seen mine above 235 once.
 

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@stumblinhorse is right on. Turning the fan start temp down to about 210* works to keep the motor cool in most situations, but not if you have to run fairly hard for extended periods of time. When he and I talk about climbing a long grade, we are talking 15 minutes with no breaks at 3500+ RPM in thin air. There's just not enough cooling capacity to keep the average built jk(u) cool under those conditions. I've added capacity with the aFe radiator, but won't know for a few months if it, combined with the lower fan start temps, lets me climb the hill like the average econobox, or even my tow rig grossing 15000lbs.

With all due respect to those of you deferring to FCAs engineers, those guys are bound by constraints I care nothing about. Government fuel economy nonsense and emissions regs come to mind. I just want my crap to run well and for a long time. Their other considerations are just noise.

Mark

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I hear the fan at 228-229 on long slow heals but if i can maintain at list 30-40 mph- temp drops to 210-215
Grill inserts are covering 30-40% of the grill openings - this might lead to overheating.
Hood insulation - which is good to have for winter but i would remove it for the summer.
And of course radiators maintenance- it might look clean from outside but in between are packed with dirt and three down. I use a flash light to see through and asses how bad radiators are clogged.
 

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Wow am I glad I don’t have over heating issues. I have never seen my EVIC go even to 220. I have wheeled out in the desert at about 105 degrees and still never saw it go high. I was crawling along over the rocks though. I would imagine that crawling along is much better for temperature control though.
Driving out there on the freeway and on highway 62 it never had any problems either though.
 

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Discussion Starter #52
Went off-roading today. Took out grill inserts and I think it made a significant difference. On 1hr highway drive to trail I was on average at 208 degrees with a range of +\- 4 depending up/downhill. The trail I did had steep grade and about 1,000 ft elevation gain in first couple miles. I saw a high of 219 on trail but was mostly 210 or below. It may be to early to tell but I think removing grill inserts / engine cover worked to an extent. Earlier this week I tested on the highway (flatter drive) and I was averaging around 222-228 degrees. So far it’s seemed to provide enough of a temperature cushion to avoid overheating. My awareness of the potential issue will also help me avoid in the future.
 

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Wow am I glad I don’t have over heating issues. I have never seen my EVIC go even to 220. I have wheeled out in the desert at about 105 degrees and still never saw it go high. I was crawling along over the rocks though. I would imagine that crawling along is much better for temperature control though.
Driving out there on the freeway and on highway 62 it never had any problems either though.
Im just curious, if you let it idle with AC off at what temp fan will kick in?
On mine fan will kick in at 226-228f (JKUS build 2017)
With AC on temp is lower though.
 

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I tried grill inserts, they made my Rubicon run hotter, and come up to operating temperature faster. Which was a plus, running hotter in traffic was a minus. I experimented and removed them, ran it, and reinstalled them only to find my engine running hotter again. Programming the fan to kick in sooner would help, however I think the engineers screwed up on this and the JK needs a bigger cooling system, with fans that kick in sooner. Removing the engine cover, and cowling along with the hood vent mod helped quite a bit, but it still runs too hot for my liking.
 
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Went off-roading today. Took out grill inserts and I think it made a significant difference. On 1hr highway drive to trail I was on average at 208 degrees with a range of +\- 4 depending up/downhill. The trail I did had steep grade and about 1,000 ft elevation gain in first couple miles. I saw a high of 219 on trail but was mostly 210 or below. It may be to early to tell but I think removing grill inserts / engine cover worked to an extent. Earlier this week I tested on the highway (flatter drive) and I was averaging around 222-228 degrees. So far it’s seemed to provide enough of a temperature cushion to avoid overheating. My awareness of the potential issue will also help me avoid in the future.
That is good news.

The main reason most don’t see high temps off road and I do is they are in 4Lo and ‘D’rive and they are shifting like crazy, thus the hot trans oil message. In my 6sp I don’t shift very much, I will rev up an stay there longer...
 

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Im just curious, if you let it idle with AC off at what temp fan will kick in?
On mine fan will kick in at 226-228f (JKUS build 2017)
With AC on temp is lower though.
The highest temperature I have ever seen on my EVIC is 217. A couple weeks ago I was out in the desert and let my Jeep idle for over an hour charging a drone battery (gotta love that AC converter on the center console). It was in the morning and only about 65 degrees but I never heard the fan come on. Like I said I am glad I don't have any engine heat issues.

I don't have grill inserts and I have my air dam in place, so maybe as others have said that is part of the system. I will be going out to the desert next weekend and will let it idle to see if it comes up enough to start the cooling fan.
P.S. My transmission has gotten almost as hot as my engine on the trail before though, if I remember correctly I think it got up to around 200.
 

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P.S. My transmission has gotten almost as hot as my engine on the trail before though, if I remember correctly I think it got up to around 200.
Note that it is a known JK (actually WA580) quirk that the transmission temp PID shows the same as coolant temp when the transmission is in Park or Neutral, so you must be in a drive gear to get an accurate reading. This has gotten me a couple times, as in I looked and saw that my transmission temp was over 200F and then I realized that I was in Park. Dropped down into gear and it read 160.
 

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This thread has me curious so I took a test drive while monitoring OBDII PIDs for coolant temp and fan speed. Ambient outside temp was in the low to mid 80's and I did whatever I could to try to raise coolant temperature, slow crawling, steep hills, sandy wash, idling, A/C, etc. and noted some interesting things. For one, the fan (or at least my fan) does not delay coming on until the 220's, in fact it starts at about 205 (variable speed, and I saw around 30-50% duty cycle (fan speed) to keep it there.) Throughout the run doing all I could do to try to raise the coolant temp it remained at 205 or below, except when I got frustrated at being unable to push the temperature very high and I tried plowing through a sandy wash and extended idling, where I managed to get a peak of 210. That was the highest I saw all day. Most of the time I was running around 205, which makes sense since that's when the fan started to come on. Again, this was all data direct from the ECU (and verified visually to the extent that I could.) I even tried running the A/C (felt decadent), but it didn't really make any difference temperature-wise, maybe the fan ran a bit harder and that's it.

So if anyone is seeing something different, especially overheating every time they go out, then it would be interesting if people could try connecting a code scanner and look at actual realtime data to see what is going on (something like the Jscan app and an OBD adapter works fine, and is only about $45.) Could some vehicles be calibrated differently? All I can say is that not only was I unable to get the temperature out of normal range no matter how hard I tried, the coolant temp was actually very well controlled. For reference my vehicle is a 2014 JK Rubicon w/4.10, auto, 2" lift, 34" tires, and a winch.
 

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Good work. What PID are you using for fan speed?

Mark

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Good work. What PID are you using for fan speed?
There are a slew of fan PIDs but the ones I was looking at were 'Fan on' (just a simple on/off indicator), 'OBD Fan Speed' (the commanded duty cycle), and 'Fan Speed' (the actual duty cycle, and of course this should match 'OBD Fan Speed'.)

It's worth noting that you should not use audible fan noise as your indication whether the fan is running or not because I saw duty cycles as low as 18%, where the fan is spinning quietly but actually moving a fair amount of air. You won't hear this although you can see it when looking at the fan from the engine compartment. At 30-50% you can hear some fan noise when standing in front of the vehicle, and above that the noise becomes much higher and it starts to become audible inside the vehicle.
 
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