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Reducing underhood temps ??

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Old 11-07-2017, 08:50 AM   #1
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Default Reducing underhood temps ??

I was wondering what would be some simple methods of reducing underhood temps? Someone recently mentioned to me that i should remove any insulation from under the hood, and any seal or gasket along the back edge/cowl area to allow heat to escape easier. Not sure if thats a good idea. I've seen blocks that lift the back of the hood an inch, that i dont particularly like, and I'm not against the idea of putting louvers in the hood but am concerned about rain water dripping down on top of everything under there. So...what say you all?
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Old 11-07-2017, 09:10 AM   #2
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I have gone for blocks that lift the rear of the hood. Have them installed in the summer and then remove them in the winter. Also keep a piece of pipe insulation in the trunk for wet days to stop water getting in there when I am parked.
Also found that my front diff skid plate has helped lower temps; think that this has to do with the air flow under the jeep.
I have found that these things help to keep temps down and like that there was no permanency associated with them.
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Old 11-07-2017, 09:55 AM   #3
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I would go the route of hood louvers:

https://www.hylineoffroad.com/jeep_p...j_hood_louvers

But if your cooling system is in good shape and motor running an normal temps, why do you feel you need to reduce the underhood temps?
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Old 11-07-2017, 11:54 AM   #4
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Just to add my 2, louvers aren't going to let in enough water to matter. A lot of off road Jeep's, with no additional waterproofing, fjord rivers and big puddles regularly with no ill effects to the motors themselves. The only real time you need to worry about water is if it's over exposed wiring, or if there is a direct route into the engine. Hood blocks would concern me for the former. Louvers wouldn't have any concern.
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Old 11-07-2017, 01:32 PM   #5
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Originally Posted by SexyDexy View Post

But if your cooling system is in good shape and motor running an normal temps, why do you feel you need to reduce the underhood temps?
Cooling system is fine, running at 210 consistently, but my hood always feels so [email protected] hot and i thought maybe it would be beneficial to let some of that trapped heat out.
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Old 11-07-2017, 02:46 PM   #6
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Cooling system is fine, running at 210 consistently, but my hood always feels so [email protected] hot and i thought maybe it would be beneficial to let some of that trapped heat out.
eh, if your temps are fine I wouldn't even bother
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Old 11-08-2017, 07:51 PM   #7
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Being in Las Vegas, we have a fair amount of heat here for a lot of the year. I installed Napier Hood Louvers and that helped immensely. I drive it through the car wash, and not water on top of the engine to worry about.
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Old 11-10-2017, 07:51 AM   #8
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Being in Las Vegas, we have a fair amount of heat here for a lot of the year. I installed Napier Hood Louvers and that helped immensely. I drive it through the car wash, and not water on top of the engine to worry about.
Was there an insulating mat under your hood? And if so, did you remove it or just cut thru it when you installed the louvers?
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Old 11-10-2017, 11:57 AM   #9
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Napier's hood vents are designed to prevent water/snow from easily entering the engine bay. In a deluge they would probably still let water in but significantly less than other designs, the vents have a lip at the bottom that works to channel water away, but the trade-off is a bit less ventilation. At speed I think they would still extract heat, and once parked any ventilation above the intake/exhaust manifold will significantly reduce temperatures.

http://www.napierprecisionproducts.c...t-LB-HV-LB.htm

You could make some drip pans like this, but it will further reduce the effictiveness of the vents, I think the Napier vents would do a fine job on their own.


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Old 11-10-2017, 12:31 PM   #10
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All of my XJs have always run pretty warm under hood temps. My wife had a 2000 model Sport that had the Pre-Cats on the exhaust manifold. It always ran warmer that any of the others that I have had/have. The 2000 also had the heat soak issue with the fuel injectors. I did not want to cut into the hood for vents, so used insulation on the fuel rail and injectors. It helped some. An idea given to me by someone was to pull the intake/exhaust manifold and wrap the exhaust manifold with header wrap all the way to the collector, or past the oil pan. He had done this to his, and he said it had helped his under hood temps considerably. We sold the 2000 before we got to try this, so I cant say if it worked. It does make since, because that is where most of the under hood heat comes from with the 4.0s. The wrap would transfer most of the heat back past the engine compartment. I will try it here shortly when I replace my cracked exhaust manifold on my 97.
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Old 11-13-2017, 07:01 PM   #11
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I ran the poly hood blocks for a while but removed them. Hot air exiting the hood gets sucked right into the cowl that supplies the interior air; so the interior would get hooter rather than cooler.
Hood louvers work well & I have had zero problems from rain and/or snow. I was trying to cool my 4.6 so put on as many louvers as I could fit. The underside pic shows how I used a step bit to swiss cheese the hood cross members to maximize air flow out the louvers.
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Old 11-13-2017, 08:07 PM   #12
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I ran the poly hood blocks for a while but removed them. Hot air exiting the hood gets sucked right into the cowl that supplies the interior air; so the interior would get hooter rather than cooler.
Hood louvers work well & I have had zero problems from rain and/or snow. I was trying to cool my 4.6 so put on as many louvers as I could fit. The underside pic shows how I used a step bit to swiss cheese the hood cross members to maximize air flow out the louvers.
any hood left? Shoulda just went hoodless! Haha
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Old 11-13-2017, 08:47 PM   #13
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any hood left? Shoulda just went hoodless! Haha
Har, har. Think my Jeep's about a 100 lbs lighter now.
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Old 11-13-2017, 11:50 PM   #14
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Quote:
Originally Posted by SexyDexy View Post
I would go the route of hood louvers:

https://www.hylineoffroad.com/jeep_p...j_hood_louvers

But if your cooling system is in good shape and motor running an normal temps, why do you feel you need to reduce the underhood temps?
If you go this route, make sure you read and understand the instructions before you buy.

If you install them as per the instructions, about 1/2 of those louvers will be non-functional.
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Old 11-14-2017, 09:16 AM   #15
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Must add- the louvers look good too!!!!!!!!!!!!!!!!!!!!!!
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