Know-How Notes: Inside Your Radiator
The largest component to your vehicle’s cooling system is the radiator, but did you know that the radiator is also connected to your transmission and in some cases your engine’s oiling system too? Inside your radiator are smaller radiators that help keep your transmission fluid and engine oil cool as well.
The basic radiator consists of two tanks with a set of tubes connected with thin fins that radiate heat away from the tubes. As air passes through the fins, the heat is carried away, lowering the temperature of the fluid running through the tubes. Modern vehicles use aluminum radiators, most with plastic side tanks, but there are also copper and brass radiators. Aluminum is used because it is light and the tubes can be made thinner, allowing the radiator to have more cores (sets of tubes) than a comparable copper radiator. This is what makes an aluminum radiator more efficient, copper actually conducts heat better than aluminum, but the extra core increases cooling capacity. Aluminum is also cheaper to manufacture.
Tanks For The Memories
Astride the cooling core, are two tanks. Some are plastic, some are aluminum or brass. Aluminum or brass tanks are welded to the core, while plastic tanks are attached with tabs and a seal. The tanks hold the coolant, one is the intake side, one is the outlet. Most modern radiators are of the crossflow variety, meaning the coolant flows from one side to the other. Some units use a 2-stage cross flow, where the tanks are split in half, forcing the coolant to flow through the radiator twice, increasing the cooling capacity of the radiator. Many older vehicles, pre-1970s, use vertical flow radiators, where the coolant enters the top of the radiator and flows down to the bottom tank. This is less efficient and has not been used much since the late 1960s.
The core itself consists of flattened tubes connected with a web of thin fins. The air is pushed or pulled through the fins, pulling heat away from the tubes. Each set of tubes and fins is called a row or core. Most aluminum radiators have four cores, while copper/brass radiators typically have two cores. Copper/brass cores are nearly twice as thick at aluminum, and even though copper and brass are better heat conductors, the ability to add more cores with aluminum makes aluminum cores more efficient when stacked up.
Cooler Than Nothing
Nearly every modern vehicle these days has an automatic transmission. In order to function, the transmission fluid needs to be cooled. If the transmission is run without a cooler, it will quickly reach 300 degrees, which will destroy the fluid and subsequently the transmission. You could use a stand-alone transmission cooler, but your vehicle’s transmission actually operates better at around 160-200 degrees than it does when cold. By placing the fluid cooler inside the radiator, the engine’s coolant helps bring the transmission up to temp faster and maintains a consistent temperature better than a stand-alone. If you are towing, however, an extra cooler, used in addition to the radiator trans cooler, will help keep the transmission from overheating. The cooling tubes for the transmission cooler are usually located inside one of the tanks.
Much like the transmission cooler, some vehicles have an oil cooler mounted in the tanks. This is most commonly used for trucks and high-performance vehicles, but not exclusively. Keeping the engine oil cool increases the engine’s performance, longevity, and allows for longer oil change intervals. When oil heats up, it starts to break down. Where transmission fluid can reach 300 before breaking down, engine oil starts this process at just 240 degrees, which is very close to operating temps of 200-220 for modern engines. Reducing that oil temp is critical, especially for high stress engines like trucks and high-performance vehicles. These cooling tubes are also usually found in one of the coolant tanks.
Nearly every modern vehicle uses a reserve tank to serve as the overflow tank and filling point of the radiator. Before these tanks, there was an overflow tank that would hold excess water in the event of a purge from the radiator cap, but the coolant was not returned to the radiator, so you were left with low coolant. Over time, this was developed into a strategy where the reservoir tank takes in excess coolant when the water expands as it heats, and returns it back into the cooling system as the coolants cools. This prevents the old problem of losing coolant.
Whether you are needing to replace a stock radiator or upgrade to increase your cooling capacity, the right sized radiator is available for your car. Just be sure that the inlet and outlet are in the right place and the right size. Direct-replacement radiators for just about every car are available at your local NAPA AUTO PARTS Store.
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