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Old 01-21-2020, 11:53 PM
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Lets talk under hood cooling

so sometimes in the middle of summer we often go wheeling. I plan to go more this summer. it often gets 100+ outside, mix in slow crawling, it can get hot under the hood.

I got some hood louvers but in my opinion i am starting to not like the cheese grater look on my AEV build. I am leaning towards getting a heat extracting hood like a 10a, or AEV but not sure yet.

Many moons ago when i owned a 07 SRT8 charger, and on those summer nights while sitting in the staging lanes we had a mod called the "25 cent" mod where we pulled the fan relay, and added a small jumper cable to make the fans come on high as soon as you plugged it in (even with the car off). This really helped with getting heat soaked motor in the staging lanes and really helped out with a head soaked engine bay. Has anyone head anything like this for the JKs? do hand held tuners offer this option?

I would love to add a nice thick radiator but i see the majority still has issues with whats available on the market right now. Does anyone else have any ideas or mods they have done to help keep under hood temps down?

To be clear, I always make sure my resivior and coolant levels are good, and i have not had any over heating issues. I just wanna help on those hot days. This winter i am going to perform a coolant flush, and possible new thermostat just because they are cheap and easy. i have about 70k on my 14 JKU.

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Old 01-22-2020, 12:00 AM   #2
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This is very topical at present. In the middle of a Sydney summer it will regularly hit 35c - 40c (95F - 104F). It can get as high as 45c...

My JK gets camshaft position sensor errors when the engine bay is very warm so I'm trying to cool it down (hoping that keeping the PCM cooler may help)

I've just taken off the hood insulation blanket and I was looking at adjusting the PWM fan duty cycle to help.

My engine runs at 98c - 108c so it is not overheating but the engine bay is like an oven.

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Old 01-22-2020, 12:13 AM
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Originally Posted by limaynard View Post
This is very topical at present. In the middle of a Sydney summer it will regularly hit 35c - 40c (95F - 104F). It can get as high as 45c...

My JK gets camshaft position sensor errors when the engine bay is very warm so I'm trying to cool it down (hoping that keeping the PCM cooler may help)

I've just taken off the hood insulation blanket and I was looking at adjusting the PWM fan duty cycle to help.

My engine runs at 98c - 108c so it is not overheating but the engine bay is like an oven.
does removing that blanket help at all? I would love to help that hot air escape at minimum.
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Old 01-22-2020, 12:59 AM   #4
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does removing that blanket help at all? I would love to help that hot air escape at minimum.
The jury is out. I took it off because my engine bay was hotter than Alice Springs at midday.

I've got a diablosport PCM on the way that will allow me to adjust the fan duty cycle but I doubt that will help with much. I've been told to take the weatherstrip at the back of the bonnet (hood) off to allow more airflow.

Others swear by vented bonnets other say it doesn't matter but when I look at the state of the plastic split loom around the wiring harnesses then I think that the heat can't be good.
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Old 01-22-2020, 01:34 AM   #5
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If your engine temp gauge stays in the middle, even on hot days, you’re not overheating. So there’s no point in modifying your fan switch, changing radiators, installing vented hoods etc.
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Old 01-22-2020, 03:12 AM   #6
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That's not the point. The engine runs within the correct range but the engine bay runs hot, they are two different things. I am happy for my engine to run at 105c but do I want my engine bay at 75-80?

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Old 01-22-2020, 04:15 AM
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If your engine temp gauge stays in the middle, even on hot days, youíre not overheating. So thereís no point in modifying your fan switch, changing radiators, installing vented hoods etc.
that's not what i am talking about.
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Old 01-22-2020, 05:53 AM   #8
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Subscribed. I'm still looking for ways to get things under the hood cooler. The OE louver modification on my Rubicon Hard Rock helped, a bit, along with removing the cowl weather stripping, and engine cover during the summer. But I still feel there's room for improvement.
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Old 01-22-2020, 06:07 AM   #9
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I got some hood louvers but in my opinion i am starting to not like the cheese grater look on my AEV build. I am leaning towards getting a heat extracting hood like a 10a, or AEV but not sure yet.
Don't those heat extracting hoods use outside air flow to draw heat from under the hood? How fast does the jeep need to go to make this happen vs how fast do you wheel?
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Old 01-22-2020, 06:50 AM   #10
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Originally Posted by limaynard View Post
This is very topical at present. In the middle of a Sydney summer it will regularly hit 35c - 40c (95F - 104F). It can get as high as 45c...

My JK gets camshaft position sensor errors when the engine bay is very warm so I'm trying to cool it down (hoping that keeping the PCM cooler may help)

I've just taken off the hood insulation blanket and I was looking at adjusting the PWM fan duty cycle to help.

My engine runs at 98c - 108c so it is not overheating but the engine bay is like an oven.
I see similar temps with my 2014 JKUS auto up here in Brisbane, but havenít seen any error codes popping up yet. I donít like seeing that gauge creeping up, but Iíve noticed it happening more on hill climbs and the beach recently. With the bar work, Gobi rack and gear I carry I do ride heavy, so Iím sure that doesnít help.

Iím going to check my radiator cap to see if itís working properly, but have also considered a new hood with heat extractors (great excuse to buy new stuff!!). I know the 3.6 tends to runs hot, but with our consistent high temps here down under I wonder if it needs a bit more help than our northern hemisphere friends, particularly with added weight.
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Old 01-22-2020, 10:59 AM   #11
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I noticed a significant amount of heat escaping after I pulled my front fender liners. If complete removal is not an option there are a couple vented replacements. I think ACE Engineering makes one. Perhaps there is a similar design readily available for you upside-down boys in AUS
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Old 01-22-2020, 04:52 PM   #12
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I noticed a significant amount of heat escaping after I pulled my front fender liners. If complete removal is not an option there are a couple vented replacements. I think ACE Engineering makes one. Perhaps there is a similar design readily available for you upside-down boys in AUS
I put mine back in recently. I don't want to cut holes in the bonnet so maybe the fender liners are the way to go. Mine throws the code at highway speeds and I'm not 100% sure it is heat related but we're working our way through it.

Maybe I'll move to Scotland (or some equally cold and wet place) to see if that helps :-)
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Old 01-22-2020, 09:08 PM   #13
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It looks like some of the programmers (but not all) allow you to change the fan-on temp
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Old 01-22-2020, 09:42 PM   #14
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It looks like some of the programmers (but not all) allow you to change the fan-on temp
I have Diablosport PCM on the way. That allows you to do it but I'm not sure it will help on its own.

Maybe reducing opening temp of the thermostat and having fan come on sooner will cause the engine to run cooler and that will allow engine bay heat to dissipate more quickly.
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Old 01-22-2020, 10:55 PM
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can anyone confirm which tuners allow you to control the fans? I may look into some sort of vents to grant them into the factory fender wells
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Old 01-22-2020, 11:01 PM   #16
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can anyone confirm which tuners allow you to control the fans? I may look into some sort of vents to grant them into the factory fender wells
Diablosport = Yes
Superchips = No?
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Old 01-23-2020, 12:59 PM   #17
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I noticed a significant amount of heat escaping after I pulled my front fender liners. If complete removal is not an option there are a couple vented replacements. I think ACE Engineering makes one. Perhaps there is a similar design readily available for you upside-down boys in AUS



Just an idea. If you are using the OEM fender liners you could customize them. A few vents or holes would be an easy mod. A couple minutes with a hole saw drill bit and you could duplicate some of the vented aftermarket liners.
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Old 01-23-2020, 04:39 PM   #18
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O.K., I live in hot as hell Phoenix. I cut about 3" off of the bottom of my inner fenders. I removed this from the front to the shocks. This helps the fan air flow better in and out of the engine area. Just think about it, some install bigger radiators, and or more efficient fans, but if the air flow doesn't have a way out, then it's not going to do much good. I have also kept my air dam on, and do not have objects (B Bars, lights and winches) blocking my air flow. I also got rid of the engine cover, and flush my radiator externally monthly during the Summer. My engine temps do not run as hot as many complaints about, while it is hot under the hood trimming the inner fenders helped.
I got this idea, when I looked at my Grandson's Colorado ZR2. It's cooler under the hood, and the engine temp just doesn't go above 210. The ZR2 has a nice large opening in their inner fenders.

Try it, you may like it...
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Old 01-23-2020, 05:10 PM   #19
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It's probably worth considering where FCA engineers thought the JL would best vent heat. Not surprisingly, right next to those big old exhaust manifolds. Hmm, are the JL fender liners any different?

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Old 01-24-2020, 02:20 PM   #20
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Undo the 2 hood latches. Let the safety latch hold the hood down. Free extra cooling when wheeling.
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Old 01-24-2020, 02:41 PM   #21
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Undo the 2 hood latches. Let the safety latch hold the hood down. Free extra cooling when wheeling.
Is that really a smart idea? I'd think that's not smart, but hey, what do I know? Maybe at low crawling speeds it wouldn't hurt anything. I was working under the hood one hot summer day (drunk) and when I was done forgot to reconnect the straps. When I took it for a drive the next day, at about 25mph the safety latch snapped and the hood flew up and smacked my light bar, destroying the hood. Lesson learned for me! I'll never have a Jeep without a light bar!

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Old 01-25-2020, 07:57 PM   #22
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Is that really a smart idea? I'd think that's not smart, but hey, what do I know? Maybe at low crawling speeds it wouldn't hurt anything. I was working under the hood one hot summer day (drunk) and when I was done forgot to reconnect the straps. When I took it for a drive the next day, at about 25mph the safety latch snapped and the hood flew up and smacked my light bar, destroying the hood. Lesson learned for me! I'll never have a Jeep without a light bar!

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Maybe fabricate some blocks to keep the hood up a couple of inches and some hood strap extenders to keep it down? A warning light to remind you it is not latched down :-)

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Old 01-25-2020, 11:04 PM   #23
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can anyone confirm which tuners allow you to control the fans? I may look into some sort of vents to grant them into the factory fender wells
HPTuners software.

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Old 01-28-2020, 05:07 PM   #24
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Why stop with hood vents, I added vents on the sides of my Jeep. You can really feel the heat escaping when it is running. This opening is much larger than the opening of my Hard Rock hood.
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Old 01-28-2020, 05:11 PM   #25
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Why stop with hood vents, I added vents on the sides of my Jeep. You can really feel the heat escaping with it is running. Thi opening is much larger than the opening of my Hard Rock hood.
Where did you get vents from?

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Old 01-28-2020, 05:22 PM   #26
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Where did you get vents from?
From Amazon of course. Ebay has them too. Paint them to match what you are doing. They are held on with double sided 3M tape. I used an air nibbler to cut the hole. That tool does not distort the metal and you can change direction anytime. Smooth the edges and paint to prevent rust. Stick on grill and stand back and admire.

https://www.ebay.com/itm/NEW-ALPENA-...gAAOxyzHxRO24q

https://www.harborfreight.com/16-gau...ler-96661.html

I was inspired by the JL side vents. Mine are much more fuctional though.
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Old 01-28-2020, 06:00 PM   #27
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From Amazon of course. Ebay has them too. Paint them to match what you are doing. They are held on with double sided 3M tape. I used an air nibbler to cut the hole. That tool does not distort the metal and you can change direction anytime. Smooth the edges and paint to prevent rust. Stick on grill and stand back and admire.



https://www.ebay.com/itm/NEW-ALPENA-...gAAOxyzHxRO24q



https://www.harborfreight.com/16-gau...ler-96661.html



I was inspired by the JL side vents. Mine are much more fuctional though.
I am in Vancouver at present, a lot of JLs with those vents. I wonder if someone will make a JK retrofit?

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Old 01-28-2020, 09:08 PM   #28
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'95 YJ with electric fan & Mishimoto radiator. fan is controlled by temperature switch, not computer. Came with a louvered insert cut into the hood. Never had a cooling problem. Only upgraded the radiator because of a leak. A simple toggle switch in parallel with the temperature switch will let you control the fan manually. It shouldn't be hard to come up with a way to monitor the temperature under the hood.
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Old 01-28-2020, 09:35 PM   #29
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There is another way to get more heat out. It's more expensive, but works great and looks cool.

If you have a shop or guy that does hood louvers in your area, you can have the hood done with more louvers. You'll have to strip that area of paint, punch the louvers and then repaint. You can also buy louvered panels that rivet or bolt in, but I'm just not a fan of them personally.

Here's a hood a local guy did on an XJ of mine years ago. 208 louvers.
It made a big difference in my operating temps as well as how fast my engine compartment cooled down:


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Old 01-28-2020, 09:36 PM   #30
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