Radiators are the heart of a vehicles cooling system, without them there would be no way to keep an internal combustion engine from overheating to the point of catastrophic failure. In this article we will explain the different kinds of radiators, different materials used in construction of them and hopefully everything else you will ever need to know about this very important piece of equipment.

Radiators come in all shapes and sizes, depending on the space constraints and requirements of the vehicle it is installed in. A large vehicle used for extreme service such as a tow truck will have a multiple-row high capacity radiator while a small commuter car will have a much smaller radiator with a lot less capacity. While radiators are also available in what is known as “high-efficiency” configurations, they are for the most part built on an industry standard unless specially made or ordered otherwise. There are 2 different styles of radiator used in the automotive industry; cross flow and top flow.

Top Flow: As the name implies, a top flow radiator takes in the hot coolant from the engine on the top row of the radiator and cools it as it flows downward to the bottom. Top flow radiators are mostly seen on older vehicles, as they aren’t as efficient at cooling the antifreeze as the newer cross flow design. Top flow radiators tend to be much taller than cross flow ones, which has become a problem in the more aerodynamic vehicles produced today where under hood space it at a minimum.

Cross Flow: Cross flow radiators are what is used in today’s vehicles due primarily to space constraints, although they tend to be more efficient as well. The coolant mixture is pumped into the radiator at one end and forced across the radiator by the water pump, utilizing more cooling tubes in the process, thus cooling the fluid more efficiently. These radiators tend to be shorter and wider than the top flow designs.

Regardless of which design your vehicle has in it, radiators all work on the same principle, they are basically a large heat exchanger. Hot coolant/anti-freeze mixture is pumped from the engine into the radiator where it is forced into smaller tubes, these small tubes run the width or height of the radiator depending on the design (Top or Side flow). The tubes have small fins attached to them that act as heat syncs, which dissipate the heat through absorption and air flowing across them through the front of the vehicle or by the fan pulling/pushing air through the radiator. The more fins per square inch, the more efficient the radiator is at dissipating the heat and keeping the engine cool.

Radiators all consist of a few basic parts, the tanks and the core. The tanks on a radiator are the sides or top and bottom where the hoses attach and the coolant enters and exits the radiator. Some vehicles incorporate coolers inside of these tanks to help keep other fluids at optimum temperatures. Automatic transmission equipped vehicles use coolers in the radiator tanks to cool the fluid to prevent the transmission from overheating and failing. Vehicles that have tow options will sometimes incorporate an engine oil cooler into the radiator to help keep the internal engine temperatures at a safe level, though some manufacturers will use engine oil coolers just to help stabilize the engine temperatures as a standard feature. A radiators core is where the real magic happens. The core consists of the small tubes and fins that actually dissipate the heat. Radiators come with different amounts of these tubes or “rows” as they are called in the industry. A truck with a tow option may have a “4 row” radiator which is very thick, where as a small import may only have a “1 row” which is more than enough for the application, but considerably thinner. The amount of rows and the size of the radiator are taken into account when the vehicle is being designed, a radiator that is too big for the engine is not necessary, but too small and you will have overheating issues.

Over the years the materials used in radiator construction have changed dramatically. Older vehicles used heavy brass construction, while newer vehicles use an aluminum core and plastic tanks. Brass radiators worked very well for many years, but material costs and the environmental impact of the materials used to solder them together (lead mixtures) have all but phased them out. Newer designs are lighter, just as efficient and don’t use solder to hold them together, they are basically clamped together with rubber gaskets. When an aluminum radiator has been replaced, the old one goes to the recycling yard where the parts are then reused to make the same products again, cutting down significantly on heavy metals and environmental impact. Radiators for performance applications are usually custom fabricated to the application and are made of aluminum tanks and cores to withstand the severe vibrations and heat of performance applications

If you suspect that your radiator has a leak or other problem, this can usually be found out with a minimum of tools. Do not open the radiator cap when hot, the coolant inside will burn you. Wait until the vehicle has cooled down to remove the cap. Once removed, verify that the rubber-sealing ring on the bottom of the cap is in good shape and isn’t torn or missing, this is a common leak. If it is good, verify that the radiator is full and use a flashlight to look for leaks where the tanks attach to the core (center) of the radiator; this is a common place for leaks as it is where the pieces are attached to each other. On plastic tank radiators, the tanks themselves can crack or become brittle and break for no real reason other than age, this usually occurs behind or near where the hoses let the coolant back into the radiator from the engine, when it is hottest. 

It is recommended to replace plastic tank radiators when they have leaking issues due to the metal fatigue in the aluminum cores and the fact that the plastic becomes brittle from heat and age. Radiators as with all automotive replacement parts come in a vast array of quality levels. Always remember that you get what you pay for with automotive parts, a cheaper radiator will consist of thinner plastic tanks and a thinner aluminum core which will not last as long or perform as well, actual fitting issues may arise as well. When it comes to the heart of your cooling system, always use the best OEM (Original Equipment Manufacturer) quality parts or the equivalent for long lasting service and reliability.

If further technical assistance is needed, ask our team of certified car repair technicians.

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Written by
Co-Founder and CEO of
35 years in the automotive repair field, ASE Master Technician, Advanced Electrical and Mechanical Theory.


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Article first published (Updated 2013-08-16)