We’ve seen the scenes in the movies, the vacationing family stranded on the side of the road, staring forlornly at the front of their car as it shoots steam into the air, refusing to go another mile. Generally, we have a sense that there is a radiator involved somehow in that crisis, but we might know exactly how. Let’s examine what a radiator does, what can go wrong with it, and how to keep it happy and your car on the road.

When you are shopping for a car, it is easy to focus on the color and style. That can be distracting, fun, and also important. But, the radiator is an unsung hero and you want to be sure that the radiator on your used car or rebuilt title car is in working order.

Knowledge is power, so when you are taking a closer look at your possible car, asking informed questions about the radiator will send a clear signal that you are paying attention.

What Exactly Does a Radiator do and Tips to Keep it Happy

(Markus Spiske/Unsplash)

How Does a Radiator Work?

A car engine generates a vast amount of heat. Pistons are shooting up and down and belts are churning. That creates heat that could cause serious damage to all the intricate parts of an engine. The radiator is a key component in the car’s cooling system. Cars can’t exactly sweat to keep themselves cool, so they are designed to cool themselves down in other ways.

There is a thermostat in the engine that is tasked with the job of keeping track of temperatures and communicating with the radiator if that temperature climbs too high. If the thermostat sends the heat signal, the radiator sends coolant and water throughout the engine to absorb the excess heat.

That coolant and water pick up all the extra heat buzzing around the engine and bring it back to the radiator. There, the radiator blows air across the hot liquid to cool it down, and all those thin metal fins help blow that hot air out of the engine to the outside air where it naturally dissipates.

The system is sort of similar to how our body circulates oxygenated blood throughout our body, picks up the deoxygenated blood, and then breathes it out as carbon dioxide. It is an impressive system, full of essential parts to keep everything running smoothly.

Since this is an article about cars and not anatomy, let’s take a look at some of the key components of the car’s cooling system.


This could be considered the “lungs” of the radiator. This is the central element of the cooling system, the place where the cooling fins vent the air that comes from cooling down the hot liquid that just went through the engine. Once that liquid is cooled off, it heads back to do it again. This is the hub of the cooling action.

Pressure Cap

The coolant tanks are pressurized so the coolant can’t boil as it is absorbing heat from the engine. The caps that hold that pressure in, therefore, are very important!

Inlet and Outlet Tanks and Hoses

These are the veins and arteries of the cooling system. Water and coolant are constantly circling in and out of these tanks and hoses heating up, cooling down, and drawing that dangerous heat away from your car’s engine. While not nearly as intricate as our circulatory system, they certainly play an important role in a car’s health.


The thermostat is the foreman of the operation, delivering messages to the radiator about overheating dangers.

Water Pump

Yep, this is the heart of the system. The water pump provides the power to flush the water and coolant through the tanks and hoses as needed to keep everything running “cool.”

What Could Go Wrong?

Now that we have a better understanding of how a radiator works, it is worth examining what it looks like if something goes wrong with the system.

Coolant Puddles

If you see regular leaks under your car, it is time to check all your fluid levels. It might not be coolant, but if it is, top it off quickly! Sometimes a coolant leak means a cracked radiator. It could be a minor enough crack that the leak is very slow, and as long as you watch your levels, it will be fine. But, the crack could also be major and will need to be addressed immediately. If your car can’t “breathe” properly to cool down, then you could deal with a total shutdown in the future.

Thick Coolant

If you find coolant puddles and the coolant is thick, sludgy, or discolored, then that is another sign of a troubled radiator. This is more than just a leak, this is a radiator that might be suffering from rust or breakdown and is deteriorating into the coolant fluid.


This is a quick sign to spot. If your car engine is overheating with some regularity, get that radiator into the shop as soon as you can! Sometimes a car will simply shut down if it gets too hot. That doesn’t mean it is beyond repair, but the longer you wait, the more expensive those repairs will be.

How to Prevent Damage

There are a few things you can do to keep everything clean, cool, and running smoothly. Radiator troubles are no fun, but they aren’t inevitable.

  1. Use the Right Coolant. It might seem obvious, but double-check your user’s manual and make sure you are using the right type of coolant for your engine. Once you go with a coolant, only use that kind of coolant. Don’t mix them. Save cocktails for the bar.
  2. Flush It. Once a year, or every 30,000 miles or so, give that radiator a flush. That will help prevent rust and buildup that can wear a radiator out before its time.
  3. Check the Hoses. With each oil change, make sure your radiator hoses get a good look. Regular inspection will prevent leaks. While you’re looking, check on that pressure cap and gaskets.
  4. Watch the Fluid. The coolant is a great fluid to check regularly, even every fill-up. It is so essential to the health of your engine, it deserves a little attention.
  5. Watch your Weight. Well, watch your car’s weight. Extra weight means extra work. Extra work means extra heat. If you find that you are loading your car down and sensing it having to work extra hard with regularity, it might be time to consider a bigger vehicle.

As you shop for your next car, ask for maintenance records. When was the last time the radiator was flushed? Have any hoses or caps been replaced? These questions will help you get a picture of the condition of the cooling system.

Radiators, like our lungs and heart, hum along most of the time, doing their essential job and keeping us happy. With a little attention and care, they’ll do that for a very long time. If we ignore them, they will get our attention in some very loud, steamy, and expensive ways!