A COOLER SOLUTION : Jeep XJ Cherokee 4.0L Cooling Problems And Cures

Anyone who has ever owned a Jeep Cherokee XJ has had to deal with engine cooling issues at one point or another.  The inline 4.0L six-cylinder engine has a great reputation for being reliable and lasting for more than 200K miles, but it can also heat up when you’re rock crawling, hauling heavy loads, or driving up a steep, long hill in hot weather conditions.

Over the decades, off-road enthusiasts have found many solutions to their XJ Cherokee Cooling problems, but some have not always determined the root causes. The most common issues arise from cracked or worn hoses, a stuck thermostat, a bad fan clutch, or a worn-out water pump. But when all those things are working properly, and the engine still overheats, other factors are at play. Rock crawling or a worn motor mount aren’t commonly seen as causes of poor cooling, but they are often the issues that can lead to persistent overheating.

Extreme rock crawling can twist the XJ’s unibody and cause radiator leaks.

Because the Jeep XJ has a unibody and no steel frame, it twists during extreme rock crawling causing the radiator to crack and leak over time. According to Matt Dawson at Champion Cooling Systems, Jeep XJ owners call and complain that their relatively new radiators are leaking just like the old ones they replaced. “It’s a common call we get from Jeep Cherokee owners who rock crawl,” says Dawson. “Those Jeeps without frame stiffeners or a roll-cage twist enough to add stress across the factory radiator core support, and over time, the radiators will crack and leak,” he said. “We’ve heard of cases where the factory plastic tanks have popped open from the stresses, leaving the Jeep owner stranded.”

Jeep XJ Cherokee Cooling Problems May Be Related To Something Else

Likewise, a broken motor mount doesn’t sound like a related cooling issue, but on Jeep XJs, a worn motor mount can go unnoticed for a long time until they cause a crack in the factory exhaust manifolds, or if it allows the engine to move so much, that it forces the factory fan clutch to into the radiator under load.  This was the case with our 1995 Jeep XJ which began to have excessive cooling issues which we could not figure out.

The cooling system in our XJ was working properly, with no leaks, and with a relatively new thermostat and water pump. Under normal conditions, the engine would get hot but not overheat under heavy loads or when traveling up long highway hill climbs on 90F+ degree days. This was a condition we lived with for a long time until we began noticing that this summer, the engine temperatures would approach the boiling point (about 260-degrees) from short trips around town.

A severely worn motor mount allowed the fan clutch to move into the radiator.

Our first thought was that the fan clutch was starting to go bad, so we first opted for a very popular upgrade among XJ owners, which involves swapping out the factory fan clutch with a heavy-duty unit from a Jeep Grand Cherokee. Using the larger fan clutch, (Haden #2796), the fan stays 100-percent engaged longer, providing more airflow at low engine speeds. On a factory system, this works extremely well, except some XJ owners don’t like the rushing sound of air that it makes. In reality, it’s the same sound as the factory fan, it only lasts longer.

The factory clutch on the left doesn’t stay engaged as long as the new one from a Grand Cherokee on the right.

When It Comes To Jeep XJ Cherokee Cooling Solutions, Bigger Is Better!

While that provided some improvement, it didn’t cure the overall problem. With our high mileage engine, our next thought was the factory radiator was plugged and flowing less coolant through it. We opted to install a larger radiator.  A factory replacement would have been the least expensive alternative, but we thought if this was the issue, it wouldn’t make any significant improvement. Instead, we opted to go with a larger, all-aluminum radiator from Champion Cooling Systems.

Champion’s all-aluminum radiator is a bar and tube design, which is stronger and has a thicker core.

The aluminum core and side tanks of the Champion radiator would provide higher heat dissipation over the factory copper core and plastic tanks. We used Champion’s #BC1193 for the XJ Cherokee, which is the same width and height as the factory radiator but has a thicker core.

According to Champion Cooling’s Matt Dawson, this radiator is a bar and tube design, as opposed to the traditional radiator tube and fin design. “The bar and plate design radiator is much like an intercooler, where each tube, flat plate, and fins are stacked together and braized as a core, then welded to tanks,” said Dawson. “This eliminates the need for a header. In a bar and plate design, the header is removed to eliminate one less piece that can fail. There’s no expansion in the radiator, and it is much stronger and more efficient at dissipating heat.”

For XJ owners, that means less strain on the radiator during rock crawling, and more surface area for heat to dissipate. In addition, Dawson pointed out that the cooling fins on their radiator have louvers to improve airflow and heat dissipation. The radiator comes from Champion ready to install and has factory fittings for the transmission cooler.

Look At the Big Picture When It Comes To XJ Cherokee Cooling

We began by removing the Grand Cherokee clutch and factory fan assembly, as well as the factory electric auxiliary fan. Once we pulled the radiator, we noticed the damage from the fan clutch. While the new Grand Cherokee clutch installs much closer to the radiator, there was about a 1/2-inch gap of space. At some point, the factory clutch had pushed into the radiator, causing fins to seal closed, but not enough to leak.

The engine movement was the result of a worn motor mount. The rubber on one side of the mount had disintegrated, exposing the center bolt sleeve. It allowed the engine to move when under load but stayed put under normal driving. We replaced the mounts and began installing the Champion radiator.

We used Champion's three fan kit with an aluminum shroud, temperature sensor, wiring harness and relays.

Realizing that by installing this radiator, there’s not enough room for even the original factory clutch fan unit, we opted for the Champion fan and shroud kit for this particular radiator. The kit consists of an aluminum shroud, three 10-inch high-capacity S-blade fans, and includes wiring, temperature sensor, relays, and wiring connectors. We also opted to change the fan’s wiring leads to waterproof connectors for our own peace of mind, as well as using one relay for each fan to avoid any overload when they kick on.

The Champion radiator fits into the factory location perfectly, re-using the factory mounts and bolts. Because the radiator is slightly thicker, we had to grind off some tabs off of the radiator core support, so it would fit flush across the radiator and allow enough clearance for the hood latches to close properly. This may only be for 1990-1995 Jeep XJ models, as later model radiator supports are slightly different.

Modifications May Be Required.

With the radiator installed and the hoses connected, we installed the fan and shroud. This slid into place, noting that in some cases, the factory A/C condenser lines may need to be pushed away slightly to allow clearance over the electric fan on that side. Once installed, we wired the fans to their appropriate relays following the instructions on the kit. The system also operates off of a temperature sensor, which allows them to turn on after the coolant temperature reaches 190 degrees. To do this, we removed the factory temperature sensor on the thermostat housing and replaced it with a brass T-fitting that has the same 3/8” NPT threads, with one male and two female ends. We also used a 3/8” NPT male-to-female adaptor to allow space between the factory and Champion sensors.

To mount the temperature sensor, we used a 3/8-inch NPT T-fitting on the factory thermostat housing. We used a male-to-female adaptor to mount the factory temperature sensor.

Once wired up and installed, the fans come on at 190-degrees and keep the engine extremely cool. With the A/C on during a 90-degree day and driving the XJ uphill, the temperature never exceeded 210 degrees on our factory instrument gauge. Idling in traffic, the temperature crept up but remained consistently a hair over the 210-degree mark. As soon as we were moving again, and more air flowed through the radiator, the temperature would fall below the 210 mark.

The upgrade to the Champion aluminum radiator and fan kit worked better than we had anticipated, and was well worth the effort. Knowing that you don’t have to constantly watch the temperature gauge at any time while you’re driving, allows XJ owners to enjoy their vehicles much more than they already are.

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About the author

Dan Sanchez

Dan Sanchez is an off-road and automotive high-performance enthusiast with a 35-year history in the automotive industry as a journalist, editor, author, and is a SCORE International 4x Journalist Of The Year.
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