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Jeep Heat Dissipation Project

by Robert Yates

Note from Stu:   A big thank you goes out to Robert.  When I heard that Robert was going to be doing some major heat reduction modifications on his '98 TJ, I mentioned that I would be glad to share the info with others if he wanted to take the time to snap some photos along the way and do a write-up.  Robert shared his dual battery installation with us some time ago.  I was able to help with that install while visiting him during a road trip.  I wasn't able to help with this one (one's real job can certainly get in the way of doing the fun stuff).  A lot of good info has been included in his write-up and I hope you find it useful should you decided to adopt some of the changes for your own vehicle.  I appreciate Robert taking the time to share this via the web site.

And now Roberts's write-up.....


My 1998 Jeep TJ (6 cylinder, 3 speed automatic, 4:56 gears and 35" tires) has always run on the warm side during the summer months at highway speeds. For additional reference, I have swapped in a Novak 2 row aluminum radiator, Hesco high flow t-stat housing and water pump and I have removed the transmission out of the engine cooling circuit completely. Whether in stock configuration with the 30" tires and 3:73 gears or the current configuration, the temp gauge has operated in the "zero" of the 210 indicator on the dash gauge. This equates to 224* in actual water temperature.

Now folks might be questioning the validity of the dash gauge seeing as its filtered through the computer and normally I would agree with that line of questioning and in fact at one time I did agree with it. In order to assure myself of what was actually happening there was some rather extensive testing performed on my rig using a mechanical gauge as well as an IR temp gun.

The bottom-line is that my rig only sees about a 10* temperature drop across the radiator. There are several theories about why this is happening and myself, I believe the culprits are the AC condenser (which operates at 325*) and its close proximity to the radiator as well as the constrained size of the radiator itself. Since I cannot do anything about the grill size and my wife would have my head if I ripped out the AC, I needed to look at living with the situation. For that I determined that the best I could do was to build in additional cooling reserve and by that I mean an oil cooler.

In doing IR gun testing on my existing radiator mounted oil cooler, I found that if my water temp was 220*, my oil temps would be similar at the output line back to the engine and depending on the situation, even higher by up to 9*. Not good. Research said to me that oil temps at 200* are about optimal so I set that as my goal. I also determined that pulling my off-road camper trailer put additional strain not only on my cooling circuit but also on my transmission circuit so that would need to be addressed as part of this project and lastly, I determined that having my exhaust ceramic coated would also aid in temperature control under the tub as well as inside the exhaust.


The above photo is my engine compartment in its current configuration with dual batteries, on-board shower heat exchanger and ARB compressor, there is not much room left for anything of size to be mounted under hood. That meant that I needed to look to other areas on the Jeep in which to mount an engine oil cooler. As I had previously ran my engine oil through the Novak radiator only to find that it actually added 9* to my oil temperature, I had to get real creative.


We put the Jeep up on the lift and began to identify areas of dead space that would allow enough room for a cooler and what came out of that was that the rear passenger corner was about the only place left on my rig that had enough available space.

My main concern with that location was the length of the run and whether or not the stock oil pump could effectively handle it.

After some discussion with an inline 6 source over on Pirate 4x4 wherein he clued me into farm equipment applications for the 6 using remote coolers, I was confident that if it were properly engineered, the run would be of no consequence.

More TJ Engine Cooling



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