Auto Radiators 101

What Is an Automotive Radiator and How Does It Work?

Your radiator is an integral part of your car or truck's cooling system. It allows the immense heat generated by your engine to be dissipated more easily into the air, keeping the engine running at its optimal temperature. A problem with your radiator can be a big problem for the overall functioning of your car, truck, or SUV. Although the operating principles for an automotive radiator are fairly straightforward, there are a lot of fine details you may want to know if you're having any trouble with your radiator.

Before we get to anything more complicated, let's start with the basics. The radiator is at the front of your car or truck's engine bay, behind the grille. It attaches to a large metal frame called the radiator core support. This, in turn, is connected to the frame of the vehicle. The radiator is usually attached by a pair of brackets at the top, and rests on a set of rubber bushings at the bottom.

The radiator itself consists of a number of tubes through which coolant flows. The tubes are in between two tanks that hold coolant at the inlet and outlet. Attached to these tubes in the radiator core are fins, which radiate heat into the air (hence the name). These can be made of different types of conductive metals designed with different number of cooling areas or cores, and have different coolant flow patterns all with their own particular advantages and disadvantages (but let's not get ahead of ourselves).

The cooling process begins when the water pump sends coolant to the engine. The coolant goes around the cylinders and picks up some of the heat produced by combustion and friction in the engine. The heated coolant then enters the radiator through the upper radiator hose and runs through the radiator tubes, which take on the heat. The heat is then conducted from the tubes into the fins, which dissipate the heat into the air. Air gets blown over the radiator through the grill as the vehicle moves forward, but an electric fan hastens this process. Finally the cooled coolant returns to the engine to repeat its journey.

What Are They Made out Of?

Radiators can be constructed from a number of different materials. Each of these constructions has its own advantage and disadvantages. The most commonly used materials are copper or brass, aluminum, and plastic.


Older radiators were primarily made of copper and brass. This is because copper is the second best metal for conducting heat. Why not use the best, heat conductor, then? Because that would be silver, and a whole radiator made of silver would be awfully expensive, and no one would even get to see it most of the time. Copper would be difficult to form into tanks, though, so those were usually made out of brass (which is, incidentally the fifth best conductor among metals). The brass tanks would be joined to the copper tubes by lead solder.

Copper tanks were efficient at cooling but rather heavy. Copper also corrodes (think of any green pennies you've come across, or the Statue of Liberty for that matter). This can be overcome though by painting the radiator. Minor problems with these newer radiators could be repaired via soldering. This made them easier to repair compared to more recent ones.


Many automakers have been moving towards aluminum radiators in recent years, even though aluminum doesn't conduct heat as well as copper. Why would they ever make radiators out of a material that's worse at heat transfer? Well, aluminum is much lighter than copper and brass. A lighter radiator means a faster or more fuel efficient car or truck (depending on use). In addition to this advantage, it's also pretty good at heat transfer. Aluminum is the fourth most conductive metal, after silver, copper, and gold (which is not used in radiators for much the same reason as silver). The aluminum radiator represents a compromise of reduced weight but also slightly reduced (but still highly effective) heat transfer. This is proving to be a compromise that many automakers are willing to make.


Many automakers use plastic in their radiators, but to refer to them as "plastic radiators," may be confusing the point a little bit. The tubes and fins are still made of metal, either copper or aluminum, but the tanks are made of plastic. The plastic is very light, but offers little heat transfer. The core material, be it copper or aluminum, offers the advantages and drawbacks inherent to that metal.

One problem with plastic is that it does not respond to heat as well as metal. As it expands and contracts with heating and cooling, it can develop cracks which can eventually lead to leaks. Excessive heat can even cause the tanks to melt and deform. On the other hand, metal can corrode, where plastic does not.

Are More Cores Better?

Each layer of tubes and fins in the radiator is known as a row or core. You may have heard of some radiators with two, three, or even four cores. You may also have heard that more cores mean better cooling. Is this true? In principle, yes, more cores mean more surface area for heat to escape from, and in turn better cooling. That being said, just as with the question of which material to use, this becomes a bit more complicated when looked at in detail. In fact, the construction material can play a role in these calculations.

As mentioned before, more cores mean more surface area for heat to dissipate off of into the cooler air. The air reaching the fourth core, say, isn't as cool though, as the air that passes through the other ones, and can't take on as much heat. That's because the cores are arranged in layers from the front to back. By the time the air reaches that fourth row, it has already been heated by the prior three.

Aluminum radiators can actually have increased surface area without increasing their thickness too much. That's because aluminum is stronger than copper. This increased strength allows aluminum tubes to be made wider without thickening their walls, and for the tubes to support more fins per inch. With these advantages, a two-row aluminum radiator can sometimes cool better than a four-row copper radiator. Of course, each additional row adds more weight and so this doubles up aluminums weight advantage over copper.

Crossflow Vs. Downflow

There are two different designs with regard to how coolant flows through the radiator. In a downflow radiator, there are tanks at the top and bottom and coolant flows downward through the tubes, aided by gravity. In a crossflow radiator, the tanks are on the left and right and coolant flows through the tubes across the radiator, aided by the water pump. Coolant moves more efficiently through a downflow radiator. That's good right? Not so fast. For the coolant to give off its heat, you want it to spend a little more time in the radiator. Crossflow radiators are more common on more recent vehicles for this reason. Wider, shorter crossflow radiators also fit better into sleeker modern designs than taller downflow radiators. Installing a crossflow radiator into an application that originally used a downflow radiator would require some fabrication. Ultimately, which flow design you use will be determined by your vehicle's make and model.

What Are These Other Associated Parts?

The radiator works as part of the overall cooling system and so relies on a number of other parts to function correctly. Some of the more pertinent parts are the upper and lower radiator hoses, the radiator cap and the radiator overflow tank, sometimes called the coolant overflow bottle, expansion tank or reservoir.

The radiator hoses are the simplest of these. These are a pair of rubber hoses that allow coolant to flow between the radiator and the engine. They are held in place with metal clamps. The upper hose carries coolant to the radiator, and the lower hose carries the cooled coolant back to the engine. These hoses can be molded for a specific vehicle fit or flex hoses which the installer must bend into shape.

The radiator cap is more complicated than it may appear at first glance. It might seem that it simply caps off the radiator, allowing you to add coolant if necessary. It also maintains the proper pressure of the radiator, though. Inside the cap is a spring mounted plunger that controls the pressure inside the radiator. Keeping a high pressure inside the radiator actually increases the boiling temperature of the coolant. If the pressure becomes too high, though, the plunger moves and allows some coolant into the overflow tank. When the coolant cools it condenses, creating a vacuum that pulls coolant back in from the overflow tank.

What Can Go Wrong?

Radiators suffer a number of problems some of which, discussed above, are particular to their construction material and others of which are universal.

The most common problem is a clogged radiator. Coolant should be a blue or green color and about the same consistency as water. Corrosion inside the radiator can cause rust to enter the coolant turning it into a yellow or brownish sludge. This sludge flows more slowly (being, as it is, sludge), and cannot cool the engine as effectively. Engine overheating may be a sign of a clogged radiator. The sludge can also stay in the corners and leave mineral deposits, which can impede the flow of coolant and reduce the cooling capabilities of the radiator. Clogged radiators can also develop further corrosion which can eventually lead to leaks. This problem should be avoidable though, if you change the coolant at regular intervals, as described by your owner's manual.

Occasionally, radiators will develop problems from the outside rather than the inside. The exterior of the radiator can be damaged by rocks or other road debris. This can lead to punctures and leaks or to bent or broken fins. Since the fins' purpose is to increase the surface area of the radiator and radiate heat away, damage to the fins significantly dampens the radiator's effectiveness. Luckily, a tool exists, known as a radiator comb, that can help to straighten out these areas of bent fins. This will not help though if the fins are totally broken. Rust and corrosion can also affect the outside of the radiator, leading to leaks or decreased effectiveness of the radiator fins.

On rare occasions, more unusual problems can occur. If the ignition system is not properly grounded, the radiator may receive an electric charge. In aluminum radiators, this will cause electrolysis to occur. In this situation, an electrochemical reaction between the aluminum and the coolant will cause rapid corrosion of the aluminum. Aluminum may also react poorly with old cooling additives. These were designed with copper and brass radiators in mind and can cause a reaction that will eat away at the inside of the radiator. Copper tubes, because they are not as strong as aluminum, can blow out under pressure.

All the related parts can also suffer damage and keep your cooling system from operating properly. The hoses, for example can develop leaks that cause loss coolant, or kinks that keep coolant from flowing properly. Hoses can suffer abrasion or punctures from road debris, can deteriorate due to overheating, and can react to oil leaks. Oil interacts with rubber in strange ways and can make the hose become spongy or gooey and develop bulges. Looseness or deterioration of the hose clamps can also cause leaks at the connections.

A malfunctioning radiator cap can also cause problems. A cracked cap can lead to leaks. A problem with the plunger (usually attributed to corrosion of the metal spring) can lead to coolant boiling at a lower temperature and being lost to evaporation. The overflow tank can also develop cracks and leaks.

Can I Replace the Radiator in My Vehicle Myself?

If you are experiencing coolant leaks or overheating it might be time to replace your radiator. Still, it would be wise to check that other elements of the cooling system are functioning properly, first. Leaks and lost coolant may be attributed to faults in the hoses, cap, or overflow tank. These parts can be more easily replaced than the radiator itself. The radiator cap is the easiest fix; just unscrew the old one and screw on the new on.

It is certainly possible to remove the radiator on your own, but be warned that it will be a difficult and time consuming task. You will also require the use of a line wrench to disconnect the transmission cooling lines. Be sure to disconnect the car's battery before beginning work so the cooling fans don't activate while you're working. You should also drain and replace the coolant. Keep a tray or bucket on hand to catch the coolant, since it can be hazardous to pets and small children.

Need a Replacement Radiator for Your Car or Truck?

If you are in need of a replacement radiator, you have come to the right place. 1A Auto not only knows everything about automotive radiators, but we also stock the highest quality, most dependable aftermarket radiators available. We carry radiators constructed of different materials and with various numbers of cores for many cars, trucks, vans and SUVs, and at great prices!

At 1A Auto, we're here to help you get the right radiator replacement for your vehicle. You can browse our large selection of automotive aftermarket radiators and shop right here on or, if you have any questions about the product, warranty, compatibility, or simply prefer to order via phone, you can call our customer service toll free at 888-844-3393.

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