Keeping Your Cool: Cooling System Tech

Airflow is the key measurement for determining the cooling capability of electric fans. Fans that pull between 2,500 and 3,300 cfm will keep most engines cool unless you are towing, and then you’ll want 4,500 to 6,000 cfm. The common and inexpensive basket fan (left) moves 2,250 cfm and is good as an auxiliary fan, while Flex-a-lite part number 294 (right) moves 6,000 cfm and is fully shrouded to fit many full-size truck radiators.

Airflow is the key measurement for determining the cooling capability of electric fans. Fa

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If overheating only happens in traffic and at low speeds, you need more airflow. When you drive at highway speeds, you’re forcing more air through the radiator regardless of how much air the fan moves. In fact, most vehicles don’t need a fan at all on the highway unless the vehicle is towing a heavy load. But at slow speeds or a stop, the only airflow through the radiator is created by the fan.

If you have a belt-driven fan, do you have a fan shroud? If not, this could be your problem, but even a properly shrouded, belt-driven fan may not move enough air at low engine rpm to cool your radiator because the fan speed is related to engine rpm. When the engine is idling, a belt-driven fan is moving very little air through the radiator. This is when an electric fan is a nice cooling solution because it can spin at full speed, pulling maximum airflow, even when your engine is idling. Switching from a belt-driven fan to an electric one also gives you a performance benefit by completely removing the mechanical load of spinning the fan from the engine. This means more power to the wheels and even a fuel economy gain. Removing a belt-driven fan that mounts on the water pump also reduces the load on the pump. This can lengthen the life of the bearings in the water pump.

If your 4x4 runs hot all the time, not just at idle, your problem is most likely an insufficient or failing radiator. Radiators deteriorate and can clog over time, but most of the time we make performance improvements to the engine to make more power and forget that more power means more heat. This Jeep is a cooling nightmare. The radiator is too small for a decent V-8 and there’s no room for a proper fan. As it is, the electric fan is partially hanging off the top of the radiator, pulling air over the top of the core instead of through it.

If your 4x4 runs hot all the time, not just at idle, your problem is most likely an insuff

What if you already have an electric fan and you still have an overheating problem only in traffic? Then you probably don’t have the right electric fan. There are hundreds of different electric fans with various airflow specifications and mounting configurations. An electric fan that pulls 1,500 cfm doesn’t stand a chance of keeping 700 horsepower cool. You need to scale the cfm rating of the fan with the power output of the vehicle. But cfm isn’t the only factor. Pulling air through as much of the radiator as possible is important. That’s why electric fan systems with full shrouds work so well. Traditional “basket” electric fans are good as auxiliary fans on the front of the radiator when a belt-driven fan is still used, but are generally not recommended as the primary cooling fan.

In addition to airflow through the radiator, you should consider airflow in the engine compartment. If the hot air is trapped under the hood, you’ll be heating the radiator from the inside and outside when you’re idling or moving slow. The fan is also less effective if there isn’t a good path for the air to flow out of the engine bay. In some cases, cutting out part of the inner fender wells or putting louvers in the hood helps heat escape the engine bay.

While brass and copper is more efficient than aluminum, Flex-a-lite’s radiator sidetank design transfers even more heat than brass and copper. The design has fins on the inside and outside which increase surface contact and dissipate more heat: 41 percent more than brass and 135 percent more than sheet-aluminum tanks. The channels in the tanks also make mounting brackets easy to install and adjust.

While brass and copper is more efficient than aluminum, Flex-a-lite’s radiator sidetank de

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The radiator world has completely changed in the past 30 years. Way back when, a four-core brass and copper radiator was the hot ticket to keep big-powered trucks cool. Having more cores was the only way to be better at that time. What we know now is that, while a four-core radiator might be good for holding a lot of coolant, it’s not that good at letting the air flow through the core to transfer the heat to the atmosphere. The thick core is very restrictive when you try to pull air through it with a fan. That’s one reason why the auto makers went to two-core construction in the ’90s, with tubes that measure 1-inch wide instead of the traditional 3⁄8-inch. Most performance aftermarket radiators now have the same two-core design with 1-inch tubes.

Aluminum radiators are now very popular, but guess what? Aluminum isn’t the most efficient material for heat transfer. When it comes to radiators, brass and copper is. Surprised? Aluminum is favored because the strength of the aluminum allows for a thinner core with much larger tubes; this promotes superior airflow and heat dissipation over its brass and copper counterpart. Also, because of their added strength, aluminum radiators can run a higher psi cap, which raises the boiling point of the coolant. For every point of psi, the boiling point is raised approximately 3 degrees. Aluminum radiators also look cool and are lightweight. The absolute worst construction for a radiator is composite: an aluminum core with plastic side tanks. Plastic is not very good at heat transfer, and these are prone to failures, especially in off-road vehicles where there is a lot of flex and vibration.

Most full-size trucks come with good-sized radiators (height and width). You may need to upgrade from a composite, single-core radiator to a performance two-core with either aluminum or brass and copper construction. Vehicles that are more likely to have cooling problems are compact trucks and Jeeps where underhood space for a radiator is at a premium, and where you’ve likely changed out the four- or six-banger for a V-8. This is when you’ll want to fit the largest width and height radiator possible, with a high-efficiency core for the best heat transfer.