A Comprehensive Guide To Radiators: What It Is And How It Works

Your car operates at its best when the engine reaches a specific temperature, and your radiator is responsible for keeping it that way.

A Comprehensive Guide To Radiators: What It Is And How It Works

You may notice, while driving your car, a temperature gauge which has a needle that is always pointing straight up, between “H” and “C” indicators. This is because engines have an optimal operating temperature, and the temperature gauge shows if your engine is at that proper temperature.

If you’re having a really bad day, the needle will be pointing to the “H” and at that point hopefully, you’ve stopped the car. If your needle stays in the center, the engine’s cooling system is working and everything is as it should be. This is thanks in part to your engine’s radiator.

What Is A Radiator

A radiator is part of a cooling system, which you can break down into two essential parts, those being a water pump and radiator. Cars do have thermostats, but your engine can operate without one for a while, as opposed to the water pump and radiator, where if one or neither of those is working your engine will overheat and warp, and become unusable. Bear in mind running your engine without a thermostat isn’t recommended, but it is possible.

How Does The Cooling System Work

A water pump runs off of the engine’s crankshaft via a pulley system and helps to keep the coolant moving through the engine’s intake and radiator. A radiator helps to take the heat from that water and, through a series of internal tubes, dissipate it through a grating of metal fins into a large fan.

The fan should only turn on when the engine reaches a certain temperature, usually around 200 degrees, or whatever temperature needed in order to keep the engine operating at the most efficient temperature.

What Happens When Your Car Overheats

Overheating is detrimental. When your engine overheats, its cylinder head (or heads) can warp and will therefore no longer be flush with the engine block, rendering your head gasket (or gaskets) useless. When this happens it’s possible for coolant to enter your engine block and mix with the oil, which damages its ability to lubricate.

This can result in broken engine components like pistons and rods, which require a complete teardown to replace. In other words, allowing your car to overheat isn’t worth anything, except to manifest palpable disdain for your engine.

How To Prevent Overheating

If you want your engine to last, that is, if you want to prevent overheating, pay attention to your car. It will tell you if it begins to overheat, and if you start to see that needle sprint towards the “H” side of your temperature gauge, pull the car over immediately and turn it off so as to prevent any damage. This is paramount, as the more time the engine spends overheating, the worse potential problems you can get.

How To Replace A Radiator

The complete specific process of replacing a radiator is going to depend on what kind of car you have, because of how hoses and suspension components are routed, amidst the mess of other engine and fueling parts that get in the way. That said, there are some basic steps to take when replacing a radiator:

  • Wait for the radiator to cool off
  • Drain the engine coolant via a drain plug (Location of which is vehicle-dependent)
  • Disconnect the coolant hoses
  • Remove the brackets that hold in the radiator, or loosen them enough to where you can wiggle the radiator out.

Putting in a new radiator is the reversal of that procedure. Some cars will require you to remove the radiator fan, and if it’s electric it’s a simple matter of disconnecting it from the harness.

Belt-driven fans sometimes don’t need to be removed to replace the radiator, however, if they do need to be removed it’s a simple process of wedging the fan’s pulley in place while you unscrew it. This can be done with a flat-head screwdriver.

How To Change Coolant

Coolant should be changed or flushed every so often. Look at your coolant condition, including its colors and levels, about as often as you check your oil (which should be frequent).

If there comes a time when the coolant is low, this is simple to fix as all it requires is to pour some water into the reservoir. You may use coolant if you want, but water works fine as well, just as long as the coolant/water ratio is about 50/50.

If your car is consistently low on coolant, this may require some investigative work, as hoses can become corroded or even disconnected, sending coolant to the ground.

Other things to watch out for are the aforementioned head gasket condition and your radiator cap. The cap is supposed to hold pressure, and if it’s no longer doing that job then it’s time for a replacement.

Flushing coolant is a long arduous process and the simplest, easiest way to flush it is to take it to a shop and pay the $100 (or whatever your shop charges). If you insist on flushing it yourself, you’ll need a few things:

  • Coolant
  • Water Hose
  • Buckets
  • Gloves

Get the front of the car into the air by setting it on jack stands, and locate the radiator’s drain plug which is usually at one of the bottom corners of the radiator itself. The easiest way to flush the coolant is to:

  • Drain the radiator when the car is cold, which only removes about half of the car’s coolant
  • Once it’s drained fill it back up with water from the hose
  • Turn the car on for about 10 minutes or however long it takes to reach its optimal temperature
  • Turn it off and then drain the radiator again
  • Repeat this process until the liquid coming out of the radiator is clear water
  • Remember to put all coolant-infected water into those buckets, as it’s toxic to the environment and must be disposed of by trained professionals.

You can put the coolant into containers and drop it off at your local auto parts store, where they will take care of it from there.

After all the coolant has been drained, you are free to fill it back up with a 50/50 ratio of coolant and water. Fill it to the brim, and with the car running allow it to “bleed”, which is to get air out of the system. This is important, as having air in the system can lead to overheating, and we all know how bad that can get.

After you’ve filled the radiator with your water and coolant mixture, have another mixture on the side (in one of those illustrious buckets), and run the engine. You’ll see the coolant drop in the radiator, which is what happens when bubbles escape the system.

Refill the radiator with your second mixture, and run it for a little while longer to make sure no more air is in the system. After there’s no more air, replace the radiator cap and you’re all done.

Car Maintenance
Repair Tips
What Kind Of Radiator Is Best

Aluminum is the way to go, which is what most cars have now. Older cars had radiators made of copper-brass, which is weaker than aluminum and as a result, the tubing on the inside of the radiator had to be on the smaller size to avoid expanding under the heat. Aluminum doesn’t fall prey to this, or at least not as dramatically so aluminum tubes can be made bigger to handle more coolant flow.

Should You Get An Aftermarket Radiator

If you’re keeping your car stock, that is, as it was from the factory, then whatever radiator it came with is what should stay under the hood. However, if you’re looking to upgrade your horsepower, your engine will run hotter, and therefore you’ll need a bigger or stronger and more efficient radiator.

Radiators can come with two different flow designs, one called downflow and the other called crossflow. Downflow radiators have their tanks on the top and bottom of the fins, whereas the cross flow has the tanks on the sides.

Crossflow works better because coolant takes longer to flow through the radiator, working to dissipate heat for longer periods of time, but older cars that came with downflow radiators might not be able to fit a crossflow, so some slight modification might be required, which we don’t recommend. If possible always go with direct fit.

As we’ve said aluminum radiators run rampant in modern cars, but if you’re trying to increase your Ford Cleveland V8 from 170 horsepower (1975+ rating system) to 400, a new aftermarket radiator is needed. For that, you’ll need to consult a list of manufacturers that make them and choose the best one.

How To Pick The Right Radiator

Unfortunately, radiators aren’t so easy to shop for, especially if you don’t have a lot of space in your engine bay. What you should do is find a radiator specific to your model car, because otherwise, it might take some slight modification to make it fit.

If you just need it to handle your drag racer for a few pulls just buy the biggest radiator you can find, throw some zip-ties at it and call it a day. For the rest of us who want to daily drive our race cars, make sure to pick the one that fits.

A performance radiator will cost anywhere from $100 - $400, and depending on your car it could take a shop about 3 hours to install. As long as it’s properly maintained, a radiator should last about 10 years.


TYC Genera is your stop for OEM replacement radiators. They aren’t built for performance, but if your car overheats because its own blew up, you can get an inexpensive, OEM-quality replacement from TYC.

Mishimoto Radiators

Mishimoto is a popular brand among motorists looking to modify their cars as it specializes in performance parts. A Mishimoto radiator is made of 100% aluminum as opposed to TYC which includes some plastic bits. Mishimoto radiators have received mixed reviews in terms of durability in the past, however, they do come with a lifetime warranty. Mishimoto makes direct fit radiators as well as universal models.

Koyo Radiator

Decidedly a less popular brand, Koyo is based in Japan and makes radiators for all kinds of applications including OEM radiator replacement and racing, and not only out of aluminum but copper-brass as well. They’ve been in the radiator business since the 1950s, so knowledge is certainly on their side. A Koyo radiator is about as expensive, if not slightly cheaper than Mishimoto.


Denso is another Japanese brand, however, they are not tied only to radiators. Denso makes OEM replacement radiators like TYC for similar prices, but unlike Mishimoto, Denso does not make an all aluminum radiator. A Denso radiator comes with plastic tanks, and either aluminum or copper cores.

Spectra Premium

Boasting a two-year warranty, Spectra Premium makes only model-specific radiators at similar prices to Denso and TYC. A Spectra Premium radiator is put through rigorous testing, making sure they’re 100% ready for operation and even claim to exceed some original manufacturer specifications. They also make transmission oil coolers.


Behr has a comprehensive knowledge base on how radiators work and an extensive catalog for vehicles from Asian countries and hybrids. For a one-stop shop that coherently illustrates what you are about to buy and why, Behr has no equal.

These five brands are leading the market, but here are some other manufacturers that are worth taking a look at:

Remember to do some research, read reviews, and make sure whichever radiator you buy will fit without any (or too many) problems.

Brian GrabianowskiBrian Grabianowski

Avid Formula 1 fan and motorcyclist, I enjoy chocolate chip cookie dough ice cream and long rides to the beach.