What is a Radiator in a Car and How Does It Work?

Although most people have heard of a radiator, they may not be aware of its purpose or importance. Put simply, the radiator is the central component of a vehicle’s cooling system. Its main function is to monitor and regulate a vehicle’s engine temperature and prevent it from overheating.

A vehicle’s engine gives it the power it needs by burning fuel and generating energy from its many moving parts. This force and motion can generate a tremendous amount of heat throughout the engine. It is important to remove this heat from the engine during operation to avoid overheating which can cause serious damage.

What is a Radiator in Car?

A radiator helps to remove excess heat from the engine. It is part of the engine’s cooling system, which also includes a liquid coolant, hoses to circulate the coolant, a fan, and a thermostat that monitors the coolant temperature. The coolant flows through the hoses from the radiator, through the engine to absorb excess engine heat, and back to the radiator.

Once it returns to the radiator, thin metal fins release the heat from the coolant to the outside air as the hot liquid flows through. Cool air flows through the car’s grille into the radiator to aid in this process and when the vehicle is stationary. When idling in traffic, the system’s fan blows air to lower the temperature of the heated coolant and blow the hot air out of the car.

After the coolant has passed through the radiator, it circulates through the engine. This heat exchange cycle is continuous to maintain optimal operating temperature and prevent engine overheating.

Related: Why is your car engine overheating?

A radiator has three main parts: the core, the pressure cap, and the outlet and inlet tanks. The core is the main section defined by a large block of metal with rows of narrow metal fins. This is where hot coolant that has passed through the engine releases its heat and the radiator cools it down for its next run through the heat exchanger circuit.

The pressure cap seals the cooling system and keeps it pressurized. This pressure is essential for the efficient operation of the radiator as it prevents the coolant from boiling and overflowing.

The outlet and inlet tanks direct coolant to the radiator after it has circulated through the engine. These tanks manage the liquid when it is very hot.

Another key component of the radiator is the coolant itself. While not a mechanized part, it is the critical ingredient that conducts heat away from the engine and allows the radiator to do its job.


How do Radiators Work?

Radiators work through a heat transfer process called convection. When the water in the radiator is heated, the surrounding air is also heated up via convection, and this hot air is then moved around the room as the air circulates. As the hot water flows through the system, it starts to cool down.

Engines create a lot of heat in their operations they’re powered off by miniature explosives! To prevent your engine from overheating, your car pumps coolant through your engine a fluid that receives heat and carries it away from the engine block.

The coolant takes the heat generated by your engine and moves it to your radiator, which blows air across the liquid – cooling it down and exchanging heat with the air outside your car.

The radiator works by-passing your coolant through thin metal fins, which allow the heat to flow to the air outside your car much more easily. Sometimes, there is a fan that blows air across the radiator in order to carry the hot air out of your car.

Radiators come in many different shapes, sizes, and designs, but their primary function remains the same.

How your car radiator cools the engine

  • The coolant in an engine is passed through tubes inside the radiator, where heat it has absorbed from the engine is dissipated into the atmosphere, before the coolant returns to the engine.
  • Coolant enters the pipes in an overheated state, causing it to become highly pressurized (aided by turbulence inside the radiator pipes).
  • This causes the radiator cap to open at a predetermined pressure point.
  • The heat is released, allowing any excess coolant to escape into an overflow tank attached to the side of the radiator.
  • That coolant is then returned to the radiator when its temperature has sufficiently lowered.

Radiator and cooling systems vary slightly from model to model (especially in older cars versus newer models), but this is the process that the majority of systems employ.

Why is your radiator important?

A radiator is important because it is the chief way your engine vents heat during operation. A malfunctioning radiator may cause significant engine damage caused by overheating – in most cars you see the billowing smoke on the side of the road is actually caused by malfunctioning radiators!

The most common cause of radiator malfunction is physical damage, which warrants a replacement of one or all of its components. Radiator function can be impaired by expired coolant or lacking coolant levels, which can be fixed via a coolant flush.

How To Flush A Radiator?

Vehicles need regular maintenance to keep working. While many of these maintenance tasks are small and simple, they can lead to big, expensive repairs if left undone for too long.

Flushing your car radiator is one of these tasks. The radiator is the heart of your vehicle’s cooling system, sending liquid coolant (antifreeze) to various parts of the engine to keep it from overheating. Experts recommend draining and replacing the antifreeze in your radiator every five years or 100,000 miles, whichever comes first.

This process, along with running distilled water through the radiator before adding fresh antifreeze, is collectively called “flushing” the radiator. Flushing gets rid of rust and gunk that naturally builds up in your car’s cooling system. Skipping this process could lead to a cooling system blockage and, ultimately, an overheated engine.

1. Determine If You Should Flush Your Car Radiator

When to flush a radiator depends on a couple of factors. One is the make and model of your car. Some cars only hold about 6 quarts of coolant, while others can hold up to 18 quarts. Knowing your car will help you determine if it’s ready for a radiator flush.

Another factor is the year of your car. If your car is on the older side, it’s probably time to flush the radiator. If it’s older than five years especially, it’s definitely time to replace the coolant by flushing the radiator.

When to flush a radiator is also dependent on your mileage. It’s recommended you flush your radiator out about every 30,000 miles to keep your car running smoothly.

2. Make Sure the Engine Has Cooled

Once you’ve determined you need to flush the radiator, also referred to as a coolant flush, place your hand on the engine block to check if it’s hot or cold. If it’s hot, don’t open it, and wait for it to cool. Also, check the coolant temperature on your dash. As soon as your engine has cooled, pop the hood of your car.

3. Drain the Coolant

As soon as everything has cooled, look under your car to find the radiator drain petcock. The petcock is usually always located in the corner of the radiator. Once located, get a pan of some sort, such as a disposable aluminum pan from the store, and place it directly under the petcock.

When in place, remove the petcock and let the coolant drain into the pan. When it’s finished draining, close the petcock and dispose of the coolant accordingly. You can check with your local hazardous waste control organization on how to safely dispose of the antifreeze.

Tip: When draining the antifreeze, it’s recommended you wear protective gloves, eyewear, and clothing.

4. Locate the Radiator

Your radiator is a long metal tank next to your engine.  When you’ve found it, twist off the radiator pressure cap so you can begin the radiator flush.

Tip: Place the cap somewhere secure. You don’t want it falling into your car or getting misplaced.

5. Pour Water and Cleaner into the Radiator

Use distilled water and the radiator cleaner of your choice to flush out your radiator. Pour both into the radiator using a funnel, making sure all of the water and cleaner make their way inside.

Tip: If at any point you get confused, refer to the directions on the back of the radiator cleaner.

6. Close the Cap and Start Your Engine

After you’ve poured in the water and cleaner, close the radiator cap, start your engine and turn on your heat. Let your engine and heat run for 5 minutes at the minimum. Doing this allows the water and cleaner to work their way through your cooling system, removing unwanted residue.

7. Drain the Water and Cleaner

After 5 minutes of the engine running has passed, turn off your car and wait for it to cool. When it’s cool, place the same aluminum pan back under the car under the petcock. Remove the petcock once more to drain the water and cleaner mixture. If you think some water remains, start the engine so it pushes the rest out and into the pan. Then, close the petcock.

8. Add the Coolant

Using the funnel again, pour your coolant mixture into your radiator. Most cars take a 50/50 antifreeze mixture that you can purchase at any automotive store. However, it’s recommended you check your owner’s manual so you know the correct antifreeze mixture to use for your specific car.

Also, check the manual for the amount of coolant you should use. Fill the coolant to the fill line. If there’s backup coolant as you pour, turn on your car with the heat on to make it drain. Then continue pouring in the antifreeze. Place the cap back on once the radiator is full.

9. Start Your Vehicle

Once the radiator has been properly flushed and the new coolant added, turn on your car so the antifreeze can run through the system. Turn off your car after a few minutes. You have now successfully learned how to flush a radiator.

To continue to care for your car, it’s important to invest in engine oil, hydraulic oil, and other car fluids that will help with the upkeep of your vehicle.

Why do car radiators fail?

The main reason for radiator failure is a coolant leak, which can lead to the cooling system failing.

If the coolant has not been checked or topped up properly, the radiator, hoses, and hose connections will become clogged and begin to rust. Over time, such corrosion will cause small holes or ‘pinhole leaks’ to develop in the car radiator.

This will result in engine coolant loss and a need for car radiator repair – or even the complete replacement of your radiator.