Jeep Wrangler Overheating at Highway Speed – SOLVED!

Why was our Jeep Wrangler Overheating at Highway Speed? 

While searching for a solution to our Jeep wrangler overheating at highway speeds, the great folks over at Race Louvers informed us of a surprising problem. After air passes through the JK grille, much of it is free to escape below, and not through the radiator as it should. The reason for this is a lack of shroud or baffle below the radiator, and is easily solved with a little creativity. Check out the wind tunnel testing they did on the JK here - specifically the image on page 6 demonstrating this issue clearly.

Our problem

In our case, the problem was a little bigger. We have a PSC power steering cooler installed as specified in the instructions. This puts it above the lower grille support bar and makes the PSC cooler an obstruction to air flow to the lower third of the radiator as seen in the photo above. Jeeps don't have a ton of room to mess around with additional coolers and such, so we weren't sure what we could do to remedy this situation until we pulled the front end apart to have a look.

Our solution

The PSC power steering cooler became an air flow asset when we realized it could easily be relocated to below the grille support to become the required baffle. After a bit of fooling around with position, we pushed it down an additional inch and a half with some spacers assembled from hardware store parts. We hammered some 1/4x5/8x1/8 bushings into some 5/8x7/8x1-1/2 spacers after using a center punch to dimple the outside edge of the bushings for an interference fit. this keeps the longer screws (3-1/2") centered in the spacers nicely.

The PSC cooler is now about even with the bottom of the radiator, and forms a fairly close fitting baffle from radiator to winch. In the photos below you can see the new mounted position:

Our Jeep Wrangler is Overheating at Highway Speed

I would say this is likely the most effective mod to preventing high engine temps at highway speeds (55-85 mph) followed by the Hood Vents in 2nd place, and the upgraded radiator in 3rd. At lower vehicle speeds, changing the radiator fan control set points was by far the most effective mod. With all the changes working together, our JK now lives happily around 212° F, with some longer periods of around 216° while climbing grades or towing, and an occasional spike of up to 222° F during aggressive driving. 

Your solution

Now this may be just the thing you need to solve a persistent heat issue if you've got the same cooler installed, but if not - other options may need to be explored. When we first learned of this flow problem, we thought of a few ways to possibly add a baffle below the radiator using plastic, or even aluminum. It wasn't until we pulled the grille and looked at things further, that we realized not only was the PSC cooler blocking a fair bit of flow, but it could be used to our advantage as a baffle in a lower mounted position. While your solution may not be the same, with a little ingenuity, you can easily find a way to keep the high pressure air from escaping out the bottom.