Radiator How To

How to Select the Correct Radiator

Controlling a liquid-cooled engine’s operating temperature is critical to both an engine’s longevity and its ability to perform.

The radiator is aptly named, since it allows heated engine coolant to circulate to this external component and “radiate” heat to the atmosphere.

A radiator is simply a heat-transfer device.

Without it (if the water pumped was plumbed in a “closed loop,” simply moving coolant within the captive block and heads), there would be no means by which the elevated coolant temperature could release, other than migrating through the block and head material.

The engine would operate in a savage cycle, with liquid coolant quickly becoming hotter until something had to give.

The engine will begin to knock/ping as the combination of excess heat and combustion pressure exceeds the limit of the fuel’s octane.

Continued detonation beats up rod bearings and can eventually burn holes through the piston domes.

Add to this elevated oil temperature (with oil thinning out and no longer providing the needed viscosity to lube bearings, cam lobes, pistons and rings, rockers and other important components) and irreparable distortion damage to the block (decks, cylinder bores, and even possible main bore geometry) and cylinder heads (deck warping and cracking).

In other words, critical overheating can quickly transform even the best and most expensive engine into a pile of scrap metal.

Excessive overheating can also place undue pressure within the radiator, possibly exceeding its mechanical limits, resulting in cracking or bursting.

Not only do you need a radiator, but you also need to control the temperature of your engine somehow.

This is why we need to focus on radiator selection as a primary aspect of temperature control.

There are three basic reasons to buy an aftermarket radiator—you’re building or restoring a vehicle, you’re upgrading your current radiator to get better cooling efficiency, or you want to enhance under-hood appearance. Or, perhaps, you’re doing all three.

When it comes to selecting the best radiator for your application, don’t forget the basics.

Make sure that the engine’s cooling passages are clean and unobstructed.

This is often a problem with a budget engine (i.e., one with a junk yard core that was simply cleaned and painted with an unknown history, or a cheap rebuild where cooling passages are ignored).

Buying a high-dollar radiator won’t provide adequate engine cooling if the liquid can’t flow through the block.

When choosing a radiator, consider the basic design in terms of how coolant travels through the radiator (downflow or crossflow), how long the coolant travels through, radiator capacity and construction materials.

"Downflow or Crossflow"

cooling system