Hood Vents -Pro's and Con's

There seems to be an increased number of guys doing hood vents to XJ's as well as other models. I get the overall theory behind it but I am wondering, while its not an extensive mod (saw a hole in the hood and screw/rivet the vent in place) is there a real and substantial advantage.

We were out at TDS this past weekend (SoCAl desert) and Saturday's outdoor temps reached the low eighties, my XJ while out doing what it does maintained a steady 210 degrees and that was with the AC on a portion of the time.

So the question is will someone see a considerable decrease in under hood temps resulting in cooler engine temps or is it just the latest bolt on mod? I'd be willing to invest the time in money if the return on investment is there.

Your thoughts.

Hood vents will lower under hood temps slightly by allowing the heat to escape easier. Your XJ is running right where it should be at 210* though. I had issues with rain killing my TPS when I had vents installed. I built drip pans to keep the rain away from my sensors and never had another issue.

That was my next concern, rain and washing the vehicle.

I would say it is a worthwhile mod for the $$. If you're wheeling in 80* temps year round you can easily go without it, no harm no foul. But it wouldn't hurt you either. Think of it like this, would it hurt for you to place two of the same size pieces of cardboard (same size as the hood vents) in the front of your radiator at 80*? I would say no, however you and I both know it is going to reduce air flow across your radiator and engine bay, and the subconscious says......bad idea you want that air flow.!! Because it makes your system perform less work to keep it cool.
So why wouldn't you want to add the air extra air flow if it can be easily done with vents? It improves the amount of air flowing through the engine bay, helping to keep temps more easily regulated, so if your fans ever let go it may be the difference in going home and blowing an engine. This also keeps the air temp lower that is being sucked into the intake side, however minute this may be, it is still an affect of more air flow. I suppose what I am getting at is you place less strain on the cooling system by non mechanical assistance. Waterpump could last longer, fans could last longer, etc. my 02. Hope it makes sense and helps.

And to actually answer your question.... NO. You will not see a reduction in temp as your jeep is designed to run at a certain temp. What will happen is a reduction in thee mount of effort your jeeps system uses to maintain said temp, freeing up HP and TQ because it's not trying to cool down all the time.

I actually noticed an improvement in overall cooling when I removed / capped my vents as they change the way the air pressures affect airflow through the radiator. <flamesuit on>

I installed LeBaron hood vents about a year ago. I found a hood on craigslist for $50 and cut the holes in that one...didn't want to start cutting my perfectly good hood in case something went wrong. Then I had the hood (and vents) re-painted.

In terms of coolant temperature, it's really hard to determine what the difference is. Like you, I never had an issue before the vents. The real benefit is to decrease underhood temperatures. If you search long enough on the web, you'll find a "study" conducted by some folks that give actual numbers. The difference is substantial. I want to say in the vicinity of 60-80*F. The vents let out so much heat, that I'm looking through heat haze when sitting at stop lights. That's what we get for cramming a large engine with an iron block / head in a small space. The dumb pre-cats on my 2000 don't help. All of this being said, I'm sure the vents do provide and increased margin against coolant overheating. For me with the pre-cats, the also all but erase the chance of heat sock / injector vapor lock on start-up.

In terms of rain, I elected not to make drip pans. Kinda defeats the purpose. Instead, I went to HD and bought an aluminum sheet. Then I bent and cut it to fit over the IAC, MAP, and TPS. Those are the ones that might be affected by water. It is affixed to the injector rail and clamped down by the intake tube on the throttle body and just covers those sensors. I've had no issues to date. While I'll admit that it was nerve wracking going through a car wash the first time, I'm not longer nervous. Rain, carwashes have not been an issue. I also bought waterproof fabric and had my girlfriend make a cover for the vents (with small magnets around the edges) in the event that it's sitting outside in a bad rain storm. Not an issue much since I have a garage.

jls095 said:

In terms of rain, I elected not to make drip pans. Kinda defeats the purpose. Instead, I went to HD and bought an aluminum sheet. Then I bent and cut it to fit over the IAC, MAP, and TPS. Those are the ones that might be affected by water. It is affixed to the injector rail and clamped down by the intake tube on the throttle body and just covers those sensors. I've had no issues to date. While I'll admit that it was nerve wracking going through a car wash the first time, I'm not longer nervous. Rain, carwashes have not been an issue. I also bought waterproof fabric and had my girlfriend make a cover for the vents (with small magnets around the edges) in the event that it's sitting outside in a bad rain storm. Not an issue much since I have a garage.

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Happen to have any pics of this? Sounds like a good idea.

Ive had louver hood vents for over two years now with out a problem. I have them near the center of the hood about .75'' on either side of the center line. Left one is pretty much right over the intake. No problems. Under hood temps are much cooler, you can see heat waves pouring out of the vents when you stop.

I have a 2001 with the precats and had heat soak issues. Installed Genright vents and no more heatsoak. I have 12" square magnetic covers I put over them in the winter or if it's sitting outside in the rain. Driving in the rain without the covers I've never had an issue with anything electrical and they have been on for 5 years. The covers do stay on at sustained highway speeds though.

KelticTJ said:

Happen to have any pics of this? Sounds like a good idea.

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Will post up pics soon. Here's the aluminum sheet...it's very malleable; easy to cut and easy to bend.

http://www.lowes.com/pd_149171-3767...l=1&currentURL=?Ntt=aluminum+sheet&facetInfo=

I wanted to add that I also have added the Le Baron hood vents and do feel like the engine temps are better managed as a whole. We do some early summer trips out in Palm Desert with the AC on, and that's where the jeep would run a little hot, but now we are right at 200 or so all day.

You can definitely see the heat pouring out of the vents, and because of that I say it's a good thing not only for engine temps, but for all the fuel and aged electrical bits that we all now have at this point in time.

We don't get a lot of rain, but was thinking about making some vinyl covers with snaps or magnets too, just to have the safeguard if needed.

There is a product called WallZilla that is a removable and reusable self adhesive paper. I have a roll of it from an old job, and plan on trying that out at some point. It is a pretty tough material and if applied decently I could see it holding up to freeway speeds no problem.

Yes, underhood temps will be reduced. My hood vents made a noticeable difference in the number of times the e-fan runs, and the length of time it runs. I have no issues with rain, snow, or car washes and the TPS.

Has anyone modified the cowl to let the hot engine bay air escape out of there? I am thinking a few large holes cut to open the engine bay and the under cowl space up, maybe even a small fan to push air would really let the hot air escape. Using that area would also keep any water from getting into the engine bay. May not be as effective as cutting large holes in the hood but maybe it would make a big enough difference to justify doing?

Thats overkill. There is no issue getting the small amount of water that would drip on your engine from hood vents.

Am i the only one who has power washed his engine bay, and rinsed off the engine bay with a garden hose?

A few drips from hood vents are nothing to worry about.

iwannadie said:

Has anyone modified the cowl to let the hot engine bay air escape out of there? I am thinking a few large holes cut to open the engine bay and the under cowl space up, maybe even a small fan to push air would really let the hot air escape. Using that area would also keep any water from getting into the engine bay. May not be as effective as cutting large holes in the hood but maybe it would make a big enough difference to justify doing?

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Why not just add spacers between the hood and the hinge levers? Plenty of people have done that with no issue.

My coolant temperature hasn't changed with the vents, but the intake temperature does. The left vent is directly over the mess that jeep came up with when they decided that both of the manifolds on the same side was a good idea.

Anybody that is OBD2 can rock a scanner and see the before and after effect on the intake temp sensor on a hot day.

I've had the Race Ace Louvers for over ten years with no ill effects from rain on the engine other than the rivits starting to rust.

My heep still runs hotter than hell.... I think I could run with the hood off and it would still run hot.

Mega Fattie said:

Thats overkill. There is no issue getting the small amount of water that would drip on your engine from hood vents.

Am i the only one who has power washed his engine bay, and rinsed off the engine bay with a garden hose?

A few drips from hood vents are nothing to worry about.

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I'm just throwing out ideas. I think cutting holes in the hood is a bit of over kill myself ha.

Ian Christiansen said:

I have a 2001 with the precats and had heat soak issues. Installed Genright vents and no more heatsoak. I have 12" square magnetic covers I put over them in the winter or if it's sitting outside in the rain. Driving in the rain without the covers I've never had an issue with anything electrical and they have been on for 5 years. The covers do stay on at sustained highway speeds though.

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I want to do vents on my 01 for this very reason; I've been having the heat soak issue.