Under Hood Heat

ReimundKrohn

Well-Known Member
First Name
Ray
Joined
Aug 18, 2021
Messages
121
Reaction score
227
Location
Alberta
Vehicle(s)
2021 Wrangler Unlimited Islander Sting Grey
Side note, and I know this is kinda petty on my part… but this really ticks me off:
476ED3EA-E9E0-4341-99A8-A92983016CA9.jpeg

In my opinion that is a flat out marketing lie.
Was that particular to the JL Rubicon, or to the JL over the JK in general? The JL did add the functional side vents to all models for under hood air flow…..
D0666E99-A812-411A-A5FB-298E3D146D79.jpeg
 

BDinTX

Well-Known Member
First Name
Brad
Joined
Jul 18, 2020
Messages
574
Reaction score
844
Location
Dallas, Tx
Vehicle(s)
2020 JLU Rubicon Recon, 2021 JLU Rubicon
Was that particular to the JL Rubicon, or to the JL over the JK in general? The JL did add the functional side vents to all models for under hood air flow…..
D0666E99-A812-411A-A5FB-298E3D146D79.jpeg
Ours is the 2020 recon edition. Not sure if the sticker is specific to it. But all JL rubicon’s have the same NON heat reduction hood.
 

ReimundKrohn

Well-Known Member
First Name
Ray
Joined
Aug 18, 2021
Messages
121
Reaction score
227
Location
Alberta
Vehicle(s)
2021 Wrangler Unlimited Islander Sting Grey
Ours is the 2020 recon edition. Not sure if the sticker is specific to it. But all JL rubicon’s have the same NON heat reduction hood.
In that case, I don’t think you’re pickin’ nits. That there would be a flat out marketing lie.
 

Windshieldfarmer

Well-Known Member
First Name
Randy
Joined
Feb 27, 2020
Messages
892
Reaction score
1,311
Location
Wichita, Ks
Vehicle(s)
2015 JKU, 2020 JlU on order
I believe the Rubicon hood sits higher in the middle compared to non Rubicon models. I suspect this additional height keeps the engine bay modestly cooler at speed compared to the Sport. Just a thought. I don’t know if any car that is cool under the hood….none that I’ve owned.
 

Ronbo Ranger

Well-Known Member
First Name
Ron
Joined
Apr 20, 2021
Messages
106
Reaction score
191
Location
Sierra Vista, Arizona
Vehicle(s)
2021 JLU Wrangler Rubicon
I had been considering the functional hood vents the day I bought my JLUR.
But I held off so far for the reason mentioned in this thread, which has been a very good conversation. WATER 💦. I wonder if there's a way to channel water and still have functional hood vents. Now I have something to keep me up at night to think about now until this is solved.
 
Last edited:

johnnyj

Well-Known Member
First Name
John
Joined
Aug 18, 2020
Messages
194
Reaction score
368
Location
Washington
Vehicle(s)
2020 JLU Rubicon, 2003 TJ Rubicon. Gone but not forgotten: 1998 Sport, 2002 Sport, 2006 LJ Rubicon
I also modified my JLUR hood vents to be functional. Don't sweat a little rain with functional hood vents - everything in there is very well sealed up for some droplets of rain. I ran poison spider hood vents on all 3 of my TJ's in Washington rain for years - no issues. For real - the engine is 95% covered even with functional hood vents. The little bit that gets in there isn't going to hurt anything and at temperature is going to evaporate almost immediately.
 

SilverSurfer

Well-Known Member
First Name
Heinrich
Joined
Apr 2, 2021
Messages
273
Reaction score
371
Location
South Africa
Vehicle(s)
2020 JL Rubicon 3.6 8-speed Auto
It is completely normal for the engine bay to get hot, you should not be concerned about it.

Removing the hood liner is not a very good idea. If you do, heat from the engine bay will be absorbed by the metal of the hood putting the hood paint at risk of deteriorating over time. The hood liner serves a purpose (Sound and heat absorption).

But, we are Jeep owners and we loooove to fiddle, change, mod our Jeeps. Sometimes the urge to scratch where it does not itch overrides facts and our brains are fixated on modifying stuff that ain't broken 😁
 

DHW

Well-Known Member
First Name
David
Joined
May 30, 2019
Messages
582
Reaction score
1,150
Location
Atlanta
Vehicle(s)
2018 Rubicon
Occupation
Attorney
I wonder if there's a way to channel water and still have functional hood vents. Now I have something to keep me up at night to think about now until this is solved.
It's been done, see below. Although a lot of people say water isn't an issue.

https://www.jlwranglerforums.com/fo...or-your-rubicon-hood-diy-install-video.51897/

Kinda interested in the Valkyrie vents, but it seems like the individual vents are fixed and have to be bent to open/close. That I don't like.

Edit: Found one Valkyrie install video on YT and it confirms the vents are fixed and have to be bent to open. Also this guy didn't even cut the heatshield, citing water concerns, so his vents are no more useful than OEM.

 
Last edited:

Headbarcode

Well-Known Member
First Name
Mike
Joined
Aug 16, 2018
Messages
4,798
Reaction score
9,321
Location
LI, New York
Vehicle(s)
2019 JLUR Stingray 2.0 turbo
Vehicle Showcase
1
The higher underhood temps on the 2.0 is mostly due to the catalytic converter being located in between the engine and driver front fender liner.

The hood vents only have a small drain hole for water, which is directed to either side and drained behind the front fenders via the hood insulator pad. Having those vents wide open can possibly lead to a small chance of issues related to cold water washing over hot engine components. I've personally watched my coolant temp guage while driving around on hotter days in the upper 90's. I've yet to see the temps go past 200°f, with an acceleration load on the engine. As soon as the throttle starts to relax to just maintain speed, the temp quickly drops at least several degrees.

Technically, they are correct as far as the hood being able to help with heat. It is aluminum, which is much better at absorbing and releasing heat than their stamped steel counterparts. Steel absorbs heat and just radiates it in all directions, thus blocking any further absorption.

@wiborcame up with a great solution, in my opinion. He opened up the factory vents and insulation pad, similar to what's already been pictured in this thread. But he used a specific material that allows heat to pass through, but doesn't allow water to drain unchecked over the top of the hot engine. If memory serves, he was able to maintain the factory drainage towards the fenders. Maybe he can chime in with his thoughts, now that some time has passed. We all know his jeep is no stranger to the elements.

Another benefit of the vents not being wide open is when fording water. The hood creates a bit of an air bubble that helps keep engine bay water levels in check. A fully vented hood would allow that same water level to rise higher when forming the same depths. It's why many say that it's best to keep a bit of momentum through deeper water. Enough to maintain the wake caused by the leading edge of the vehicle, that way the water doesn't get as big of a chance of infiltrating the intake tract.
 

DHW

Well-Known Member
First Name
David
Joined
May 30, 2019
Messages
582
Reaction score
1,150
Location
Atlanta
Vehicle(s)
2018 Rubicon
Occupation
Attorney
@wiborcame up with a great solution, in my opinion. He opened up the factory vents and insulation pad, similar to what's already been pictured in this thread. But he used a specific material that allows heat to pass through, but doesn't allow water to drain unchecked over the top of the hot engine.
IIRC he used Frogzskin.
 

Wabujitsu

Well-Known Member
First Name
Jeff
Joined
Jul 26, 2019
Messages
1,325
Reaction score
2,453
Location
Sarasota, FL
Vehicle(s)
2021 JLUR, 2020 Sahara
Occupation
Retired US Army
Vehicle Showcase
1
The higher underhood temps on the 2.0 is mostly due to the catalytic converter being located in between the engine and driver front fender liner.

The hood vents only have a small drain hole for water, which is directed to either side and drained behind the front fenders via the hood insulator pad. Having those vents wide open can possibly lead to a small chance of issues related to cold water washing over hot engine components. I've personally watched my coolant temp guage while driving around on hotter days in the upper 90's. I've yet to see the temps go past 200°f, with an acceleration load on the engine. As soon as the throttle starts to relax to just maintain speed, the temp quickly drops at least several degrees.

Technically, they are correct as far as the hood being able to help with heat. It is aluminum, which is much better at absorbing and releasing heat than their stamped steel counterparts. Steel absorbs heat and just radiates it in all directions, thus blocking any further absorption.

@wiborcame up with a great solution, in my opinion. He opened up the factory vents and insulation pad, similar to what's already been pictured in this thread. But he used a specific material that allows heat to pass through, but doesn't allow water to drain unchecked over the top of the hot engine. If memory serves, he was able to maintain the factory drainage towards the fenders. Maybe he can chime in with his thoughts, now that some time has passed. We all know his jeep is no stranger to the elements.

Another benefit of the vents not being wide open is when fording water. The hood creates a bit of an air bubble that helps keep engine bay water levels in check. A fully vented hood would allow that same water level to rise higher when forming the same depths. It's why many say that it's best to keep a bit of momentum through deeper water. Enough to maintain the wake caused by the leading edge of the vehicle, that way the water doesn't get as big of a chance of infiltrating the intake tract.
HUGE “like” to this post! My experience in Florida heat and water is the same. Another concern I have, which stops me from cutting the hood under my Rubicon hood vents, is a bow wave washing over the hood when entering a water crossing with speed and momentum. Besides, as previously stated, my 2.0T ALWAYS operates within normal temperature limits during blazing-hot Florida summer weather.
 

One_off

Active Member
First Name
Brian
Joined
Oct 18, 2019
Messages
39
Reaction score
81
Location
Palm Bay Florida
Vehicle(s)
2021 Rubicon 2d Gecko Gr + 2021 Rubicon 2 White
Just because your engine water temp is not over temp does not mean all the other electronic components under the hood are not experiencing them.
The radiator and thermostat control the coolant Temps to that 190ish range. Trust me many parts are getting hotter than that!
I've got a new jeep coming in a couple weeks.
I'll use some temp probes I use for testing to compare before / after Temps when I cut holes in my rubicon vent and insulation.
 

JEEPIDON

Well-Known Member
First Name
Charlie
Joined
Mar 6, 2018
Messages
604
Reaction score
871
Location
Forsyth, Missouri
Vehicle(s)
2018 Wrangler Rubicon JL, 2018 Wrangler Sahara JL, 2010 Dodge Challenger R/T, 2013 Ram Longhorn 2500, 2008 JK Wrangler Sahara
Occupation
Retired - Business Consultant
I also modified my JLUR hood vents to be functional. Don't sweat a little rain with functional hood vents - everything in there is very well sealed up for some droplets of rain. I ran poison spider hood vents on all 3 of my TJ's in Washington rain for years - no issues. For real - the engine is 95% covered even with functional hood vents. The little bit that gets in there isn't going to hurt anything and at temperature is going to evaporate almost immediately.
It is completely normal for the engine bay to get hot, you should not be concerned about it.

Removing the hood liner is not a very good idea. If you do, heat from the engine bay will be absorbed by the metal of the hood putting the hood paint at risk of deteriorating over time. The hood liner serves a purpose (Sound and heat absorption).

But, we are Jeep owners and we loooove to fiddle, change, mod our Jeeps. Sometimes the urge to scratch where it does not itch overrides facts and our brains are fixated on modifying stuff that ain't broken 😁
The hood pad has nothing to do with heat and paint, it’s a sound insulation pad. The paint gets hotter in the sun than from underneath.
on the JL it also serves to route vent water to the edge of the hood for disposal. I’ve taken my pad and sent it to the recycler and cut the sides out of the vent
3F120A30-5F00-4835-BFAA-CA3784DCBD82.jpeg
to release heat and attached a couple of hoses glued to plastic to route the water to the hood seals and out of the back of the engine compartment! It’s been this way since January 2018! Check the photo.

8AD11FD5-B76A-41F1-A4A2-78F5D99633DE.jpeg
 

SilverSurfer

Well-Known Member
First Name
Heinrich
Joined
Apr 2, 2021
Messages
273
Reaction score
371
Location
South Africa
Vehicle(s)
2020 JL Rubicon 3.6 8-speed Auto
The hood pad has nothing to do with heat and paint, it’s a sound insulation pad. The paint gets hotter in the sun than from underneath.
Sorry, you are incorrect. I do not want to school you on thermodynamics (Heat, Radiation, Conduction).

But, I will give you some clues; the difference between the paint on the hood and underneath the hood, the energy (Heat source) optimal operating temperature and the entropy of the material involved.

You are free to do what you feel is best for you, each to their own, but please do not claim your mod as scientific fact. It is nothing more than a cool non functional modification.
 
Advertisement

Hothead Headliners
 
Advertisement
Top