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Reducing underhood temps ??

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Old 11-14-2017, 11:46 AM   #16
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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?

No mat under my hood
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Old 11-14-2017, 10:48 PM   #17
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I have louvers and I can controll the Efan manually.
on my 98
-do at your own risk, you tamper with the computer- I dont know what years this may work on, i assume 97-01.

Locate pin c2 on the pcm. its in the grey connector. C2 controls the rad fan relay, when its grounded the fan comes on. splice into c2 and run the wire through a switch and to ground. no power
also, pin a12 on the pcm controls extra idle, same thing. ground it through a switch. A is the black plug on the pcm. you may have to remove the airbox to make room.
only do this if you are comfortable cutting into your wiring harness.
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Old 11-15-2017, 02:50 AM   #18
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Originally Posted by SFNM94XJ View Post
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.
that's a BEAST of a louver setup!!

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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?
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Originally Posted by TRCM View Post
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.
TECM has a VERY good point here... The cutout template doesn't cut out very much at all in terms of hood to hood louver coverage
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Old 11-16-2017, 05:01 PM   #19
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[QUOTE=SirCyber;3440185]that's a BEAST of a louver setup!!

I pretty much used up all the real estate on the hood. lol

In my experience, if you have high temp gauge issues; the real solution lies within the cooling system itself & its performance.

That said, I agree with OP; I was never happy with how hot the hood & front fenders on my XJ got after I started engine mods. Intuitively, it makes sense that opening the relatively enclosed XJ engine compartment would help with engine cooling. I'm guessing I got about a 5 -10 degree cooling drop with the louvers.

Plus, all the rubber and plastics under the hood are better off with lower temps.
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Old 11-16-2017, 10:32 PM   #20
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If you have electric fans make sure they are all functional.

If your main fan is on the motor look into replacing the fan clutch. You should also have a secondary electric fan on the drivers' side. Make sure it is functioning.

Make sure you have a fan shroud on the back of your radiator. It helps tremendously with directing the airflow.

Also troubleshoot your thermostat

If your coolant is discolored you should properly clean and flush the system. I had to do mine 3 or 4 times before it started to make a difference. My hvac heater control valve was corroding and getting junk in the cooling system. If you have a problem with yours you can eliminate it, or replace it.

Your water pump could be worn out. If you hear a screeching noise when you start your car it could be the water pump impellers rubbing the housing and shearing off metal into your cooling system. I usually wait until it breaks to replace it, rather than taking it off just to check the condition.

I would not recommend removing the shield from the underside of the hood. Over time the temperature fluctuations will cause the clear coat to oxidize and peel off the hood. The xj is already prone to peeling clear coat as it is.

Hood vents will help evacuate some of the heat. If you are standing still the motor bay on the xj is pretty much just a big box that traps the heat inside.

Last edited by craigjacob1; 11-16-2017 at 10:40 PM.
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Old Yesterday, 10:33 AM   #21
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I have often wondered how a cowl on the hood with a switched fan blowing cool air down and out the bottom would work?
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Old Yesterday, 12:14 PM   #22
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Bugout, I would go opposite... Force air up and out through a vent rather than pushing air down. Either way I suppose would work though >
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Old Yesterday, 12:28 PM   #23
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Bugout, I would go opposite... Force air up and out through a vent rather than pushing air down. Either way I suppose would work though >
I always wondered about this, because it seems it would be more efficient to pull the additional colder air from outside and force it down through it's normal pathway than to be pulling hot air out through the top. We may be "Working against the grain" per say... Especially if we are trying to prevent heat soak with this concept in the first place.

I'm thinking it would probably help greatly to cool the intake and exhaust from the top down rather than up? And the floor boards are going to get hot no matter what anyways, but it might even help with this too if the air forced through the whole engine compartment down and back is cooler over all?

It was just an out of the box thought...

Last edited by Bugout4x4; Yesterday at 12:33 PM.
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Old Yesterday, 12:33 PM   #24
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Lol they probably both would work... Anything really would help the steam box that is the xj engine bay! If, however, the problem is just how hot the hood is, just truck liner it... The rubber makes it seem not that hot anymore, trust me ��
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Old Yesterday, 12:47 PM   #25
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If, however, the problem is just how hot the hood is,
Didn't notice, was that the original complaint? lol Then don't try to put your girl friend up there then, your wife (or ex-wife) already caught on to those hood temps years ago.

Seriously... Hoods get hot by nature! lol Keeping the intake cool is what would be important here I would think?
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Old Yesterday, 12:49 PM   #26
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Amen brother... Agreed on all parts!
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Old Yesterday, 12:53 PM   #27
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Lol they probably both would work... Anything really would help the steam box that is the xj engine bay! If, however, the problem is just how hot the hood is, just truck liner it... The rubber makes it seem not that hot anymore, trust me ��
Here's one... If it just a hot hood being the problem, then just glue a big aluminum heat sink radiator on it like a CPU.
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