Cooling the engine bay

An issue I encountered on my way home from vacation was a significant overheat problem at US Customs coming in from Canada. Mind you, this was my first ever overheat problem. I had several factors that contributed to this problem. One, I didn’t clean my radiator out very well (in spite of my thinking so) from my Bass Lake wheelin’ trip. Two, this was my first time ever for towing my boat back and fourth to Canada in July, fully loaded boat and fully loaded XJ with wife and dog.


Three, I don’t know where my brains were but I pulled a newb stunt. While creeping the mile to the customs booth, AC was on and I was in gear. Rather than creeping, I should have been moving forward, dropping in neutral, then back in gear when I had to.

Well, the engine and transmission ( I have a trans temp gauge) went to max temp, the computer shut off the AC, the dash warning lights came on. So, to quickly cool things down, I rolled down the windows, turned off the AC and the heat to max on. So for the next half hour the engine slowly came back down to normal. Jeeze was that hot.

That experience prompted me to do a couple of things that I had been putting off. Venting heat from the engine and a trans cooler.

One comment I’ve frequently heard is to use a 3 core radiator to reduce the temperature. Yes, that is an excellent idea, if I needed a new radiator and that would only cool the engine. Even so, there is still the issue of under hood heat. The engine can still experience heat soak and cooler air into the manifold is a more efficient engine. So, reducing under hood heat, I would still consider important.

The venting heat from the engine is first. I’ve seen most all the methods of letting out the heat and saw the Grand Prix style vents in action. The Grand Prix style vents seemed to clog more with mud and extended further down into the engine compartment then I felt they should.

After reading GoJeeps writeup ( http://go.jeep-xj.info/HowtoBonnetVents.htm ) on air movement on the outside of the vehicle and my considering how air would move on the inside, I wanted my cutouts to be high on the hood. Lets face it, heat rises and the hood rises toward the windshield. I also wanted unrestricted air flow to maximize cooling. Again, on GoJeeps site, I used the basic idea that John Wood used. A hood scoop, reversed. I liked the style he used but was unable to find them in the States and the Australia store wouldn’t ship to the US.

I spent a couple of hours at Summit Racings looking at their scoops and finally found the one I liked best. Their part number, SUM-471102 @ $42.95 ea, nor was I concerned with the price of the modification. It was a matter of what I wanted.

The first step was laying the scoops on the hood and figuring where the cutouts would be. Obviously, I had to work around the hood support channel. Once I laid out one side with a magic marker, I used tissue paper to trace the pattern, then transferred it to the other side. I punched a half inch hole in the cut out then used an air nibbler to finish the cut outs.


Now I had to mod the scoop. I got out my dremmel tool and cut out the ABS plastic at the opening end of the scoops. Then I used to 1/16” mesh screen, cut and bent the edges for an inside fit.


Next, I used automotive masking tape and hot melt glue to temporarily hold the screen in place. Once the screen was secure, I mixed up a batch of epoxy, and coated the entire edge of the screen for a permanent fit.


I then drilled and counter sunk six mounting holes for 8/32 SS screws. Eventually, I will use some seam sealer to make the mount permanent.


The final project.


And from the dash.


So far, when at idle or slow speed, the amount of air moving out those scoops is amazing. Only time will tell on any other benefits.

rstarch345 said:

An issue I encountered on my way home from vacation was a significant overheat problem at US Customs coming in from Canada. Mind you, this was my first ever overheat problem. I had several factors that contributed to this problem. One, I didn’t clean my radiator out very well (in spite of my thinking so) from my Bass Lake wheelin’ trip. Two, this was my first time ever for towing my boat back and fourth to Canada in July, fully loaded boat and fully loaded XJ with wife and dog.

Three, I don’t know where my brains were but I pulled a newb stunt. While creeping the mile to the customs booth, AC was on and I was in gear. Rather than creeping, I should have been moving forward, dropping in neutral, then back in gear when I had to.

Well, the engine and transmission ( I have a trans temp gauge) went to max temp, the computer shut off the AC, the dash warning lights came on. So, to quickly cool things down, I rolled down the windows, turned off the AC and the heat to max on. So for the next half hour the engine slowly came back down to normal. Jeeze was that hot.

That experience prompted me to do a couple of things that I had been putting off. Venting heat from the engine and a trans cooler.

One comment I’ve frequently heard is to use a 3 core radiator to reduce the temperature. Yes, that is an excellent idea, if I needed a new radiator and that would only cool the engine. Even so, there is still the issue of under hood heat. The engine can still experience heat soak and cooler air into the manifold is a more efficient engine. So, reducing under hood heat, I would still consider important.

The venting heat from the engine is first. I’ve seen most all the methods of letting out the heat and saw the Grand Prix style vents in action. The Grand Prix style vents seemed to clog more with mud and extended further down into the engine compartment then I felt they should.

After reading GoJeeps writeup ( http://go.jeep-xj.info/HowtoBonnetVents.htm ) on air movement on the outside of the vehicle and my considering how air would move on the inside, I wanted my cutouts to be high on the hood. Lets face it, heat rises and the hood rises toward the windshield. I also wanted unrestricted air flow to maximize cooling. Again, on GoJeeps site, I used the basic idea that John Wood used. A hood scoop, reversed. I liked the style he used but was unable to find them in the States and the Australia store wouldn’t ship to the US.

I spent a couple of hours at Summit Racings looking at their scoops and finally found the one I liked best. Their part number, SUM-471102 @ $42.95 ea, nor was I concerned with the price of the modification. It was a matter of what I wanted.

The first step was laying the scoops on the hood and figuring where the cutouts would be. Obviously, I had to work around the hood support channel. Once I laid out one side with a magic marker, I used tissue paper to trace the pattern, then transferred it to the other side. I punched a half inch hole in the cut out then used an air nibbler to finish the cut outs.

Now I had to mod the scoop. I got out my dremmel tool and cut out the ABS plastic at the opening end of the scoops. Then I used to 1/16” mesh screen, cut and bent the edges for an inside fit.

Next, I used automotive masking tape and hot melt glue to temporarily hold the screen in place. Once the screen was secure, I mixed up a batch of epoxy, and coated the entire edge of the screen for a permanent fit.

I then drilled and counter sunk six mounting holes for 8/32 SS screws. Eventually, I will use some seam sealer to make the mount permanent.

The final project.

And from the dash.

So far, when at idle or slow speed, the amount of air moving out those scoops is amazing. Only time will tell on any other benefits.

Click to expand...

Your jeep is alot newer and prettier than mine, but I put 1" spacers between the hood and the hood hinges to make the whole hood sorta like a cowl induction...it doesn't look that bad but if you didn't know any better you would just think the hood was sprung. You should also mount a heater core under one of those vent for additional cooling. Looks like a good job though.

i like the look of those hood vents