Hood Vents - 4/30/03

My engine temps stay right at 200 - 210* pretty much year round on the road. Crawling down a hot dusty trail in the middle of summer is a different story however. My engine temps get up to about 235* mostly due to lack of airflow through the radiator and heat building up in the engine compartment. The electric auxiliary fan does a good job of keeping temperatures from going above that but seeing the guage read higher than it normally is on the street makes me kind of nervous. I'd rather not have to worry about that when I'm usually miles from the nearest paved road. So I've seen pictures of different hood vents that people have installed on their Cherokees and thought that this would be an excellent way to let the hot air out and hopefully keep engine temps from rising too much. By next summer I also want to swap in a 3 row radiator, which coupled with my tranny cooler and these vents should make a near bullet-proof cooling system. (Some people also replace their stock 195* thermostat with a 180* one, but because outside temperatures here also get very cold in the winter, I plan on keeping the stock one.)

photo #1

photo #2
Photo #1 and #2 : The vents I chose to use are from an 80's Chrysler LeBaron Turbo or New Yorker Turbo. A trip to my local "Pick-n-Pull" and I found several of these cars that had the vents I was looking for. They shouldn't charge you more than $5 + taxes per set of vents but first I had to pay a $2 admission to get into the boneyard wether I took anything or not. A Phillips screwdriver is all you need to remove the 4 screws from the top of each vent and they lift right out of the hood.The vents are surprisingly heavy because they are made out of thick fiberglass not plastic. They are pretty big compared to other vent styles I was looking at and measure 14.25" long and 9.25" wide at the back of the vent (they are not a perfect rectangle as the front of the vent is slightly narrower than the back). Also note that these vents are recessed into the hood a bit instead of just sitting on top. The slats are vertical not angled.
photo #3

Photo #3 : After painting your vents in a few coats of your favorite color (I chose "semi-flat" black Krylon spraypaint), you are ready to measure where you'll be cutting the holes. The first thing you want to do is tape off the area of the hood where the vents will be with masking tape. By this time my I was getting a bit weak in the knees and had butterflies in the stomach. Obviously cutting holes in a shiny hood of a 2000 XJ is going to be a bit nerve racking, to say the least! Measuring accurately is the most important part of this whole job. Remember - "measure twice and cut once" but for me it was more like "measure a dozen times and then... wait I better measure again" : ) I purposely measured the holes a bit on the small side to give me a bigger margin of error and still be OK should things go wrong. You want to make sure you don't cut the holes too big or you'll be in trouble. Most of the measuring is done on the underside of the hood. You may want to scroll down and look at photo #9 to see where the holes should be in relation to the hood supports. Ideally, you want to measure so you won't cut into any hood supports.
photo #4
Photo #4 : I placed a heavy mat over the windshield to protect it from being pitted by the flying metal particles and sparks. I also used another mat over the hood for the same reasons and to give me an area to lean on or lay the tools and not damage the paint.
photo #5
Photo #5 : "The point of no return!" I chose to use a 4.5" angle grinder with cuttoff wheel for the cutting. Because you can't cut rounded corners with this, I started off by drilling a hole in each corner to cut to and help round the corner. Drilling the first hole, I felt like I was comitting a horrible sin or something : ) But after that you realize there is no turning back and the nerves finally settle down a bit. Not completely though, because I still had to cut. Drilling the holes helped but I still couldn't cut all the way hole to hole due to the curve at the corners but got it very close. Some people use a jigsaw rather than an angle grinder and in retrospect I think the jigsaw would be the better tool to use for this job (more on that later). Either tool you use, you'll need to be careful not to sink the blade in too far because you might cut into some engine parts that in some areas are only about an inch beneath the hood. On the drivers side the stock airtube is very close as well as some vacuum lines and hood release cable. The alternative is to remove the hood from the vehicle for the cutting, but that involves a lot of extra work. It was easy to do as is with a little care. I also put a cookie sheet under the side I was cutting, but I should have also put a tarp or blanket over the engine to catch the metal particles. As a result, I had metal particles all over the engine when I was done. You can also see a hacksaw blade in the photo. I used this to saw through the remaining metal at each corner to complete the cut.
photo #6
Photo #6 : This shows both holes cut. I did a test fit of the vents and sure enough the holes were a tad too small in some areas. That was a good thing because I knew the holes weren't too big and it didn't take long with the grinder to achieve a near perfect fit!
photo #7
Photo #7 : I removed the tape and to my dismay the paint around the edges had flaked up! I didn't expect that because I had taped it off as I had seen others do. After speaking with a few people who are a little more experienced in fabricating and cutting auto bodies, we came to the conclusion that it was the heat from the cuttoff wheel that caused the flaking. This is why I mentioned above that I think a jigsaw might be a better tool for this job than the angle grinder was. Plus the angle grinder really takes a steady hand wereas the jigsaw might be a little easier to control.
photo #8
Photo #8 : I touched up the edges where the flaked paint was so the exposed metal wouldn't rust. I used black fingernail polish to touch it up since thats what I use to touch up rock rash on my bumpers and skids and it is easy to apply. Besides I didn't have any blue paint around that matched the hood. But as you can see, the overlay of the vents covers it all up. It looks perfect!
photo #9
Photo #9 : Here is a shot of the holes from the underside of the hood. You can see that it is a tight fit between the hood supports. Thats one of the great things about these vents is they fit in that spot so nicely and are as big as you can get and still retain all the supports. The downside is thats the only place to put these vents and if you want vents in a different location, you'd be better off choosing a different sized vent.
photo #10
Photo #10 : Now we need to address how the vents are held in place. The easiest way to do this is cut some angled tabs out of steel or aluminum. I bought a strip of 3/4" x 1/2" angled aluminum at Lowes. I cut tabs that were about 1" inch long out of the aluminum strip and drilled a hole for the bolt to go through. The tabs clamp the vents to the underside of the hood. The are held on very secure and so there is no need to use any glue or tape to try and hold the vents in place.
photo #11

photo #12
Photo #11 and #12 : He are some shots of how the vents look installed from the outside. In photo #11 you can see that the vents don't stick up that far from the hood. In this photo it looks like my hood is dented and some of the slats in the vent are warped. That is not the case though. I took that pic after driving the jeep so the distortion is from the heat rising out of the vents! It hasn't been hot enough here to give them a good test on the trail yet but anytime I park it or stop at a stoplight, the heat billowing out of the vents is very noticeable. I notice also that after shutting off the jeep, the engine cools down much faster than it would otherwise. Photo #12 is just a front view of the jeep. The vents are a little hard to see because of the reflection on the hood but I love how these vents look! I think it gives it a more aggressive look and the vents look like they belong on the XJ. I have gotten nothing but compliments on them from other people.

Since installing the vents (and I also recently removed the splash shield under the engine), I noticed that the engine compartment is a lot more dusty or dirtier than it has been in the past. I guess thats the trade off for allowing more airflow in the engine compartment. Looks like I'll be washing the engine more frequently than before.



What to do about water?

When driving, especially at highway speeds water does not pass through the vents. You'll notice that when moving, very little water lands on the hood. Most of the water hits the windshield or passes over the top of the jeep as it is carried by the airflow. What little water does enter would be vaporized by the hot engine and wouldn't matter either. But when parked, or during a car wash, the water can pass right through the slats. Also due to the fact that the vents are recessed into the hood, any water landing on the vents will drip down inside rather than off and onto the hood. This is a little concerning to me because I park the jeep outside and I don't think it would be good to have water dripping on the engine for long periods of time. In the winter I imagine it could freeze overnight and I would have ice on the engine. Technically a little water won't hurt but there are some electrical components that I would hate to have any problems with. The drivers side vent is right over the intake manifold. The fuel injectors, throttle body, TPS, and other sensors will get wet. On the passenger side there is less to be concerned with. Water will drip on the valve cover, spark plug "rail" (if you have a distributor cap and wires it may be more of a concern) oil filter, and a few sensors.

I asked a few people who have had these vents or similar ones and they all say that they didn't do anything about the water and that it is not an issue. I don't mind getting the engine wet every now and then like when I wash it, but I wanted to be on the safe side and keep water off of the engine as much as possible. At first I thought I'd make some covers out of plexiglass with a stip of magnetic tape that could be put on in inclement weather. I made the covers but scrapped that idea and decided to make some drip pans underneath the vents. This next section I'll show you how I made these pans.

photo #13
Photo #13 : The drip pans will be attached using the same bolts that hold the vents in, so I had to buy some longer bolts. You'll notice that the are different lengths. More on that below.
photo #14
Photo #14 : I measured and cut some thin sheet metal for the drivers side drip pan.
photo #15
Photo #15 : After tossing a few ideas around as to where and how to channel the water this is what I decided on. The corner of the vent that is in the bottom right in the picture is over an area that just misses the intake manifold and the water can drop to the ground. Actually it hits the u-joint of the front driveshaft but that shouldn't hurt anything. So I wanted to channel the water to that corner. The problem is that the vents are sloped to the front of the vehicle and there isn't much room between the airtube and the vent on that side. So I had to angle the drip pan to the middle of the hood and then toward the rear of the vehicle. There is a hole in the pan to drain the water into that "V" channel I attached to the underside of the pan. You can follow the arrows to see how the water flows. It was tricky getting the pan to slope just right and keep it high enough to clear the airtube so I can safely shut the hood. I actually trimmed down the rubber ridges on the airtube with a utility knife to get a little more clearance.
photo #16
Photo #16 : The passenger side is a lot easier and it doesn't need to cover the whole vent. I was even thinking about just skipping this side since I was mostly concerned with the drivers side. I kind of screwed up and made this too small but it does cover much of the area I wanted. I also goofed on drilling the holes and so I redrilled them and filled in the old holes with RTV.
photo #17
Photo #17 : Here is another shot so you can see the angle of the pans. They still allow heat to pass around all sides of the pans and escape out the vents. I'm sure the heat escapes much faster without the pans, but a large amount of heat still escapes so the pans don't realy defeat the purpose of the vents.

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