Down-flow Radiator vs. Cross-flow Radiator: What is the Difference?

People frequently ask us whether a cross-flow or down-flow radiator will cool their vehicle better. The answer is pretty straight forward, but to help clear up the confusion, let’s look at the main factors in radiator cooling.

There are a lot of different factors that contribute to a radiator’s ability to cool. Construction materials, methods, and design all play a role. While we’re not going to cover all the different aspects of radiator design, we do need to look at how a radiator works. The hot coolant coming from the engine flows into one radiator tank and then passes through the tubes in the radiator core to the other tank. As it flows through the tubes, the heat is transferred to the tube walls and dissipated by the radiator fins. The more tube surface area there is, then the better the radiator can cool. That is how all radiators work, so why are there two different flow styles?

Down-flow and Cross-flow Radiator Construction

The process to build either of these radiators is identical. Where the tanks are attached is the only difference. In a down-flow radiator you have a tank attached to the top and bottom of the radiator core. The coolant enters the top tank and flows down to the bottom tank. As you’ve probably guessed by now, a cross-flow radiator has tanks on the left and right side. Coolant enters one side and flows across to the other. The real question is, does that make a difference in cooling ability?

Which Cools Better?

Assuming you have a cross-flow and down-flow radiator made from the same materials and build methods, then they will provide the same level of cooling. So why the difference? It really comes down to space under the hood. Depending on your vehicle or equipment, you may be able to fit a larger cross-flow radiator instead of a down-flow. This goes back to surface area. If the two radiators are the same size, they will cool the same. In the cases where you can fit a larger radiator of a different flow style, then you can increase the cooling ability. Which radiator to use primarily comes down to the space requirements.

Multiple Pass Radiators

If your space is limited or you need additional cooling, there are radiators that will pass the coolant through the core two or more times. Typically you’ll only see double pass radiators. In this case, the tanks have baffles inside them that force the coolant to pass through the core twice. Since this means the same amount of coolant travels over twice the surface area, it has more time to cool. Some applications may even require a triple pass radiator. When in doubt, you should replace your existing radiator with one that at least matches the OEM specifications; however, if extra cooling is needed, then a double or triple pass radiator may help.

Pressure Cap Location

There is one advantage that a cross-flow radiator has over a down-flow, and that is the location of the pressure cap. All radiators use a pressure cap to prevent damage to the cooling system as the coolant heats up. With down-flow radiators, this cap has to be placed on the top tank putting it on the “high pressure” side and causing the pressure cap to vent sooner. Cross-flow radiators can have the pressure cap on the second tank where the coolant flows out of the radiator putting the cap on the “low pressure” side. This can allow more coolant to stay in the system which improves cooling efficiency. That being said, the difference is not that great and can only provide a benefit in high performance applications such as racing. You can achieve better cooling improvements by maximizing the surface area your radiator has.

Summary

The surface area a radiator has is the biggest influence on its cooling ability. Since there is no difference in cooling ability between down-flow and cross-flow radiators made with the same materials and size, you should choose whichever one better fits in your vehicle. No need in going through expensive modifications for a different flow style. In some situations, a double or triple pass radiator may help improve cooling ability. For high performance applications, a cross-flow radiator will allow for a pressure cap on the low-pressure side of the radiator helping to maximize cooling efficiency.

If you have questions regarding your radiator needs, feel free to call us at 1-800-223-4299. Our friendly staff will be happy to assist you!