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December 2007 Willie's Workbench - Overheating Engines

Posted in How To: Tech Qa on December 1, 2007
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Keeping your 4x4 running cool may or may not be your problem. A lot depends on where you live, what you're doing with the vehicle, and more so, on what modifications you've done to it.Yes, it seems strange that I should be writing about overheating solutions this time of year, but what better time is there to solve the problem? It's kind of like the old adage that says "You can't fix a leaking roof in the rain, and when it's not raining, it don't need fixing-but it's a lot easier to do."This last summer in Montana was the hottest on record, and my wife's Grand Cherokee ran warmer than I really liked it to. Of course, I could have just said, "Don't use the air conditioning," but then I might have found that my own cooking wasn't all that great.

It has this nice ARB bumper that I'm sure somewhat disturbs the airflow through the radiator, but it's got to stay. Naturally, there are some great large rectangular IPF lights on it too. At this latitude, it's still light at 10:00 p.m. in the summer, and the lights don't get much summer use, so off they came. No change in temperature at trail speeds, but on long highway grades, the temperature dropped about 5 degrees, so that was easy.

The local radiator shop said I must be doing something right in my coolant changing schedule as they declared the radiator to be in like-almost-new condition. The clutch fan was also working like it should, and the radiator cap was holding proper pressure.

Not much more I could do to improve things-or was there? Water is a better heat-transfer medium than antifreeze but not as practical, especially in the winter and with the engine designed to run at about the temperature water boils at. But what if I could improve on the water? Red Line ( makes a wetting agent, which, by breaking down surface tension, can drop water temperature by a claimed 30 degrees.

Did the water temperature drop 30 degrees? No, but it did bring the temperature back down to just above normal most of the time. While I was pouring in the Water Wetter, I got to thinking about just how all that hot air that was displaced from the radiator was supposed to get out of the engine compartment. The front bumper and the 5-plus inches of suspension lift, I'm sure, didn't do the underside aerodynamics any good, plus tubular headers added to the underhood heat load.

Back in the 1930s, nearly every car had hood louvers. Why not now? Most likely it's a noise issue. If the air can't get out, by going down and around the engine, why not let it exchange upward like it wants to go naturally? I remembered seeing on display at Moab that a company called Gen-Right (805/584-8635, was making all sorts of different styles of pop rivet-on louver plates.

A phone call and a Visa card had me a few days later with a pair of black powdercoated louver plates that were 7 3/4 x 8 inches. I would have liked to have gone bigger, but the crossbracing on the hood's underside was the limiting factor. They also came with some pretty darn good instructions and tips for installation.

I made up a cardboard pattern matching the louver plate's size, minus 1/2 inch on all sides with a hole in it dead-center. I then placed it on the hood's underside between the bracing, trimmed it to a proper fit and marked through the center hole onto the hood. I drilled 1/4-inch holes in each of the corners, and in the center. Then I was able to turn my pattern over, put a bolt through the center hole of the pattern, drop it onto the hood, square it up with the corner holes, and trace a pattern for the cut-out.

Before you start cutting, though, make sure everything is right. You only get one chance here, and tape measures do lie. I taped the area around the cut-out to prevent any possible scratches from the saw I was using. Then it was a simple job of positioning the louver panel and riveting it into place.

As you can see in the photo, with the one louver in place my hole did not match the panel. This was because of the bracing under the hood.

Did it help? For darn sure. My wife gets to use the A/C even on the hottest day, I don't have to cook my own food, and my guess is that there will be a side benefit this winter with the engine heat helping to keep the windshield free of ice and snow.

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