Canucklesammich

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I have heard of others doing this too, but just curious why it is necessary if the engine is off and you are no longer driving?
With the engine off, coolant is no longer flowing to cool the engine, so the residual heat builds up until it peaks & starts cooling off.

 

flyer92

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I do this knowing I'll be wrenching as things cool quicker. For instance, knowing I'm changing the oil when I get home, I open the hood to vent hot air and cool things off quicker. I change the oil with it on the warmer side.
Totally makes sense and agree. This is clearly a necessity if you plan to work in/on your Jeep after driving, even if you live in cool climates. I'm just trying to understand the benefit of doing this on a regular basis if you're just shutting down for the day and heading into the house.
 

Canucklesammich

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Take a look at my write up: https://www.jlwranglerforums.com/fo...waterproof-rubicon-hood-vents-write-up.82001/

I tried to "dress" my cuts with 3 different kinds of tape (duct, foil, and gold thermal tape) and have found that the engine bay gets so hot, all three tapes started to curl and none of them would stay stuck. Especially true on the drivers side. Left me know what you come up with.
I left a bit of a lip when I trimmed out the bottom; my idea was to use some door protective trim to hold the two together, but I'm not too sure that'll work. I may have cut too much off the liner, and I'm not sure I can find a size that'll fit. Since it's not visible from outside, I might just leave it before I do any more damage.
 
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PunksJL

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My reading of your chart is that the ambient engine bay temp with the vents opened up was 11, 17, and 5 degrees cooler than with the vents on, with the exception of the 3rd run being 1 degree warmer. So overall it seems it was cooler with the vents opened, correct?

Just trying to make sure I'm reading the chart correctly.
Yes you are reading that correctly. Unfortunately this seemed to have no significant effect on coolant, oil or transmission temperature which is what I was hoping for. Even though temperatures were a bit lower without the vents I felt it was pretty insignificant.
 
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I have heard of others doing this too, but just curious why it is necessary if the engine is off and you are no longer driving?
It’s not being done for the engine, but rather the under hood heat build up. For the wiring, hoses, battery, computer and fan belt. We live in hot as hell Phoenix, so a lot of heat builds up under the hood, from both the engine and sun beating down on the hood.
 


bonediggitty

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I live in the Phoenix area, and have no need to tow with my JL. I opened my vents up with a dremel.

I didn’t see any improvements at speed. Temps all fluctuate depending on driving style but coolant and oil temps regularly stay under 220*, even driving 75-80 on the highway in 115*. Occasionally I’ll catch myself trying to keep up with faster traffic, and wonder what my temps are. That’s the only time I’ve seen my coolant and oil temps in the 220s since cutting my own vents.

I do see a huge improvement creeping around off-road. While wheeling with a fellow 2022 3.6 JL, I’m typically showing sub 205* coolant and oil temps while he’s typically in the mid 220* range and even floating to 230*. 15-25 degree swing on the same trail, at the same time, in the same Arizona desert, makes me think I made a good decision.

I don’t have to worry about torrential rain and snow, so 195-205* sounds good to me when it’s 115* out.
 

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Whatever you do, Make sure that the vents are extraction vents and not intake vents.

If you force air into the engine bay, you will decrease the pressure differential between the front and rear of the radiator and actually DECREASE the flow of air through the radiator.
Technically speaking, venturi and pressure differential… there’s a reason the slats points rearward amigos.

oh yes, and engine control wants to keep everything within parameters, so drastic changes will likely not be perceived.
 

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I suspect the only real way to lower under hood temps through the hood without replacing it with some sort of aftermarket piece would be to 3D print something that fits with a scoop facing forward. As you already know, simply venting doesn’t result in a significant change.
The problem with that is that you will reduce airflow through the radiator by increasing the pressure in the engine bay, even if just slightly.

The only way to actually reduce temps with them is to use any airflow through them for heat exchange. Actively venting then may also increase airflow through the primary radiator, but without ducting that air directly from the radiator, that effect will be negligible in assisting cooling.

(Posted on mobile, forgive autocorrect issues.)
 

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The problem with that is that you will reduce airflow through the radiator by increasing the pressure in the engine bay, even if just slightly.
Theoretically, yes. Realistically, maybe. Way too many variables to say yes or no either way as a blanket statement.

The only way to actually reduce temps with them is to use any airflow through them for heat exchange. Actively venting then may also increase airflow through the primary radiator, but without ducting that air directly from the radiator, that effect will be negligible in assisting cooling.

(Posted on mobile, forgive autocorrect issues.)
Probably correct with regard to oil and coolant temps, but there’s no denying that pushing cooler air into the engine compartment will absolutely result in lower engine compartment temps.
The real question is is it enough to make a difference? I don’t think it’s significant enough to be of any real help for the overwhelming majority.
 


J_Winslow

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Sone of these "ideas" make me giggle. This is in no way trashing anyone or anything, but don't you think Jeep though about making actual hood vents when they made the fake ones???

I mean it would have 0 cost change to make the rubicon hood vents function if they inded did function, meaning they reduced heat. It's just funny to me that people seem to think that never crossed their mind and you are the first to posit the idea.
 

Chazdog

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Sone of these "ideas" make me giggle. This is in no way trashing anyone or anything, but don't you think Jeep though about making actual hood vents when they made the fake ones???

I mean it would have 0 cost change to make the rubicon hood vents function if they inded did function, meaning they reduced heat. It's just funny to me that people seem to think that never crossed their mind and you are the first to posit the idea.
The two cutouts in the sheet metal indicates to me that Stellantis at least had the concept in their plans to make hood vents that were functional. Otherwise, there would only be indentations stamped in where the plastic trays would be affixed.
I’m admittedly not a fan of factory installed decals, badges and trim pieces that are designed to enhance the esthetic of the vehicle but otherwise serve no functional purpose. Probably grumpy old man syndrome taking hold.
 

J_Winslow

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The two cutouts in the sheet metal indicates to me that Stellantis at least had the concept in their plans to make hood vents that were functional. Otherwise, there would only be indentations stamped in where the plastic trays would be affixed.
I’m admittedly not a fan of factory installed decals, badges and trim pieces that are designed to enhance the esthetic of the vehicle but otherwise serve no functional purpose. Probably grumpy old man syndrome taking hold.
I'm not a fan of "fake" vents but I do like the look of the rubi hood overall.
 

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Whatever you do, Make sure that the vents are extraction vents and not intake vents.

If you force air into the engine bay, you will decrease the pressure differential between the front and rear of the radiator and actually DECREASE the flow of air through the radiator.
Correct, I've been to the A2 wind tunnel in NC a number of times. Thus, the reason for adding hood vents is to lower the underhood air pressure and thus lower the amount of drag on the car. On a number of cars, we hook them up with instrumentation and one is, measuring air flow through the radiator. Thus hood vents help increase the air flow through it.

 

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