How can I keep engine temps down?

[Windshieldfarmer]

I have the 2.0. Running hot is not unique to the 3.6. I’ve seen 240 a couple of times running 70 mph up Eisenhower pass in Co. I just slowed things down a bit which brought temps down a few degrees. I replaced my front grill with a gladiator version which allows for more airflow. I think that helped slightly. Bottom line, these things are designed to run hot…but running hot does not contribute to longevity. Stellantis only cares about the first 60,000 miles on these engines.

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[CarbonSteel]

Bottom line, these things are POORLY designed to run hot…but running hot does not contribute to longevity.

Added a descriptor for you. 240F, all aluminum construction, and 11:1 compression ratio is perfect recipe for cracked heads and blocks.

 

[Willys41]

I have the 2.0. Running hot is not unique to the 3.6. I’ve seen 240 a couple of times running 70 mph up Eisenhower pass in Co. I just slowed things down a bit which brought temps down a few degrees. I replaced my front grill with a gladiator version which allows for more airflow. I think that helped slightly. Bottom line, these things are designed to run hot…but running hot does not contribute to longevity. Stellantis only cares about the first 60,000 miles on these engines.

I think that the 2.0 and 3.6 run under the same rad. fan specs.
The 3.6 in my case the rad. fan only comes on at 15% fan speed at 221 and 75% fan speed at 231.
I tried many different things over a 6 mouth period to lower temps including a after market radiator.
Nothing I did lowered coolant temps.
What I discovered is the radiator fins are very tight and will not allow free flowing air to pass through even running down the freeway at 65mph and this is the problem.
The only way to get air to pass through the radiator is to suck it through with the rad. fan.
After $100s spent on trying to get the jeep to run cooler I came across Jon at RPM Extreme.
He was making a fan controller for the JK and I ask if he could make one for the JL.
He got right on it and in a few weeks He had one tested and ready to ship.
His fan controller is a 5 step fan controller unlike the factory 2 step.
after the RPM fan controller my average temps are 195 and I only saw 212 once on a 8000ft mountain pass at 6600lbs on 37 tires 4.88 gears.
I have seen a 25+ degree decrees in coolant and oil temp under all driving condition.

RPM FAN CONTROLLER
195 degrees = 15%
199 degrees = 30%
205 degrees = 50%
212 degrees = 75%
218+ degrees = 100%

http://www.rpmextreme.com/Product/311/Jeep-JL-PWM-FAN-CONTROLLER.aspx

 

[dstevens]

Several factors.

Jeep's have small radiators - it has to fit between the headlights and also the axle intrusion means it is not deep. My Honda Civic has a larger radiator than my Jeep. A pickup truck has perhaps double the radiator area than a Jeep.

Lack of a decent air dam means that there is not good negative air pressure behind the radiator. People forget that the air flow over the radiator is based on the differential in air pressure, both positive and negative.

My observation is that the radiator fan makes a difference at any vehicle speed, which is not usually the case with other vehicles. This tells me that there is not good air flow through the radiator from the vehicle motion. On the JK I measured the radiator air flow at something like 1/4 vehicle speed or less.

The radiator fan control is incorrectly programmed from the factory. The fan comes on far too late to be useful, then it cycles off too quickly.

The pentastar (at least) has a single stage thermostat so the coolant only goes through the radiator based on the hose size difference between the radiator and the bypass. So some of the coolant coolant some of the time gets cooled by the radiator; the rest is hot when it re-enters the engine.

Without knowing the alloy and heat treatment I'm not sure what the temperature limit of the cylinder head is but I'm never comfortable going over 235F. I'm assuming that since ther factory shuts things down at 250F that's what their engineers decided was too hot.

 

[Soggybottomboy]

I Just got off the beach. Short 2 mile drive in very soft sand. 4H, OffRoad mode. 3000 RPMs most of the time in 1st gear. Temp was 230-233. 3.6L. I spend a lot of time on the beach and this is normal for my Jeep.

SBB

 

[Willys41]

Several factors.

Jeep's have small radiators - it has to fit between the headlights and also the axle intrusion means it is not deep. My Honda Civic has a larger radiator than my Jeep. A pickup truck has perhaps double the radiator area than a Jeep.

Lack of a decent air dam means that there is not good negative air pressure behind the radiator. People forget that the air flow over the radiator is based on the differential in air pressure, both positive and negative.

My observation is that the radiator fan makes a difference at any vehicle speed, which is not usually the case with other vehicles. This tells me that there is not good air flow through the radiator from the vehicle motion. On the JK I measured the radiator air flow at something like 1/4 vehicle speed or less.

The radiator fan control is incorrectly programmed from the factory. The fan comes on far too late to be useful, then it cycles off too quickly.

The pentastar (at least) has a single stage thermostat so the coolant only goes through the radiator based on the hose size difference between the radiator and the bypass. So some of the coolant coolant some of the time gets cooled by the radiator; the rest is hot when it re-enters the engine.

Without knowing the alloy and heat treatment I'm not sure what the temperature limit of the cylinder head is but I'm never comfortable going over 235F. I'm assuming that since ther factory shuts things down at 250F that's what their engineers decided was too hot.

One of the things I tried over that 6 months was mounting a high volume high pressure pusher fan. I tried several different configuration and what I found was that the air would go early though the A/C condenser put as soon as it hit the radiator it would bounce off and shoot out the gaps between the condenser and radiator.
I could only get about 10% air flow though the radiator. Even after I block off those gaps it still would not pass enough air to make any cooling difference.
This was the same with the factory and the Mishimoto radiator.
Today's radiators are built with very tight fins and will not free flow air very well.
All this testing should me that even driving down the road at 65mph very little free flowing air will pass through the radiator. It must be sucked through.

 

[azski]

+1 for the rpm extreme fan controller. Makes a world of difference and is the only true solution imo

 

[dstevens]

On the JK I reprogrammed the PCM to run the fan as it should. On the JL with the GPEC5 controller ... still waiting for someone to unlock the PCM. Hopefully before heat death of the universe.

 

[gato]

Late to the party, but 225F is very normal and beneficial. I actually would love to see my engine oil in the 220s more often - at least then I know I'm evaporating any moisture suspended in the oil.

 

[Valpo Jeep]

Thanks for the input everyone. It seems to want to run 225/230s down here anytime the engine is working harder going uphill in SMP. 233-235 is the max I have seen. Its got 90,000 miles on the clock and is likely the original coolant. Looks like I need to add that to my fluid maintenance schedule this fall/winter once I get home.

On a different note, the front rotors had some warpage going on before the trip but the constant heavier use has heated them up enough to scrub all the deposits off and the rotors don’t feel much of any warpage now.

 

[Ratbert]

On a different note, the front rotors had some warpage going on before the trip but the constant heavier use has heated them up enough to scrub all the deposits off and the rotors don’t feel much of any warpage now.

You were using your brakes instead of downshifting? That's sketchy AF.

 

[Valpo Jeep]

You were using your brakes instead of downshifting? That's sketchy AF.

Predominantly downshifting but there were still plenty of times that I had to get on the brakes

 

[flyer92]

225F is no big deal or concerning at all, but I personally do add a bottle of Redline Water Wetter into all my vehicle cooling systems and it helps drop temps a bit and keep them more stable.

I often see 240+ in the scorching Summers here in Las Vegas, especially when going uphill. I have been very tempted to use Water Wetter, but I'm one of those owners who religiously avoids gimmicky additives that don't work or can even cause damage.

I suspect this isn't the case for Water Wetter, but I would like to know how much you add to your engine coolant and about how much it reduces your engine temps. Seems like this could be a cheap/easy way to bring temps down, but I've been a little hesitant because cheap/easy never seems to work out well. Love to hear some testimonials from you and others who use this product regularly. Thanks in advance and appreciate your insight.

 

[Kracka]

I often see 240+ in the scorching Summers here in Las Vegas, especially when going uphill. I have been very tempted to use Water Wetter, but I'm one of those owners who religiously avoids gimmicky additives that don't work or can even cause damage.

I suspect this isn't the case for Water Wetter, but I would like to know how much you add to your engine coolant and about how much it reduces your engine temps. Seems like this could be a cheap/easy way to bring temps down, but I've been a little hesitant because cheap/easy never seems to work out well. Love to hear some testimonials from you and others who use this product regularly. Thanks in advance and appreciate your insight.

I add 1 bottle to the factory cooling system, and have been doing so on every vehicle I've owned for over 2 decades. This includes modified turbo imports, 2 Corvettes, and 4 Jeeps.

The results have been noteworthy, especially on the modern vehicles that run so hot for emissions & efficiency reasons. The WaterWetter dropped my C7's temps by 20 degrees (early C7 Corvettes ran notoriously hot) while it was good for about 10 degrees on my C8).

Redline is a legit boutique brand, owned by Phillips66. Archer Racing, famous for Vipers, is who originally got me using Redline products. I am also currently using their gear oil & transfer case fluids.

You can also go the old school route of adding a few drops of dishsoap into the cooling system to break down the surface tension, but I prefer the Redline WaterWetter product.

 

[flyer92]

I add 1 bottle to the factory cooling system, and have been doing so on every vehicle I've owned for over 2 decades. This includes modified turbo imports, 2 Corvettes, and 4 Jeeps.

Redline is a legit boutique brand, owned by Phillips66. Archer Racing, famous for Vipers, is who originally got me using Redline products. I am also currently using their gear oil & transfer case fluids.

You can also go the old school route of adding a few drops of dishsoap into the cooling system to break down the surface tension, but I prefer the Redline WaterWetter product.

Yep...I've also been a Redline customer for many years and strictly used their oil in our old imports. This is why I assume that Water Wetter actually works to some extent and why I've been considering it for my JL.

I assume that the bottle you add to the JL's coolant is the standard 12 ounce, correct?

I know that drivers of other vehicles also change the water to coolant ratio when using Water Wetter, but do you feel that's necessary for the 3.6L? Seems like this might only apply to high-performance or racing vehicles.

Lastly...about how much cooler are your engine temps with Water Wetter vs. without?

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