What Causes a Radiator to Burst?

It’s a nightmare scenario: A homeowner turns on their heating system and moments later, they hear a loud bang, followed by water spilling onto the floor. It’s the radiator, and it has burst. But what caused it to happen?

In this article, we will examine the most common causes of radiator bursts that can leave homeowners frustrated and in need of costly repairs. We will also explore preventive measures you can take to protect your heating system from such disasters.

What is a Radiator?

A radiator is simply an element that removes heat from your car’s engine. A typical automotive radiator contains fluid (most commonly water) and has several thin metal tubes called radiator hoses that connect with other engine components like your thermostat.

When you start your car, it pumps coolant through these hoses which act as a vehicle for heat energy as it travels throughout your car’s engine.

How Does a Radiator Work?

A radiator’s job is twofold: The first is to heat up your car. It absorbs heat from your engine block and passes it on through a series of tubes, where it gets dispersed throughout your vehicle by fans.

Without these fans, there would be little airflow and therefore less heat dispersal. The second function of a radiator is to cool down any over-heated areas within your car, such as when you run into heavy traffic or have an uphill climb. But why do radiators burst so often?

What Causes a Radiator to Burst?

The most common cause of radiator bursts is overheating. Usually, overheating occurs as a result of clogged coolant passages.

The blockage prevents the proper circulation of coolant through your radiator and into your engine. As your engine works harder, it needs more coolant to dissipate heat.

So if you don’t get rid of that clog or fix whatever’s causing your car to overheat you can literally cook your car’s engine. Eventually, you will have a blown head gasket or cracked cylinder head on your hands.

Damaged Radiator Tank

Sometimes it’s as simple as driving over something that punctures your radiator tank. Other times, if your vehicle is old, you might notice cracking or bulging under its exterior this can be caused by heat expansion and contraction of the metal over time.

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If you drive an older car and see that your radiator is damaged or badly rusted, take it into a shop for repair or replacement. If you hear any hissing noises from underneath your hood, immediately pull over and park somewhere safe.

Overheating Due To Water Leak

Let’s say you have a little crack in your engine and coolant leaks out. That liquid will be drawn into your car’s cooling system and pass over hot metal parts, which transfer heat into it keeping everything under control.

But if that flow of coolant is halted, or leaks into places where there is no metal for it to absorb heat from, then you could run into trouble. The best way to avoid overheating due to water leaks is to keep an eye on your vehicle’s radiator.

Leaking Head Gasket

A leaking head gasket is often to blame for radiator leaks. If your car’s radiator is running hot and losing coolant, check your engine for signs of a leak. A cracked cylinder head or cracked lower intake manifold can also cause overheating.

Check under your hood, or open your vehicle’s oil cap while it’s idling; if you see bubbles coming from these two areas, one of these is probably your problem.

Bad Radiator Cap

The radiator cap keeps your vehicle’s engine cool by releasing excess pressure from inside of it. Over time, your radiator cap can develop tiny holes that let pressure escape and cause the cooling system to fail. This will lead to overheating and eventually, damage caused by overheating.

If you see steam coming from under your hood or see an immediate temperature rise when you press on the gas pedal, chances are your radiator cap is leaking. Replace it as soon as possible!

Radiator Corrosion

The heated metal expands, so many automotive radiators are made of brass. The problem is that brass corrodes when it’s exposed to air and water.

As these materials oxidize, they create a build-up of solid material inside your radiator that restricts its cooling flow. This can cause overheating, which leads to cracking and often, total failure of your car’s radiator.

Clogged Radiator

If your car overheats, it may be because of a clogged radiator. Clogged radiators tend to happen when too much gunk builds up on your car’s cooling system. And there are lots of ways you can cause problems with your radiator.

Driving with an old or damaged water pump will cause issues, as will adding too much coolant. Leaving food or other objects near your radiator is another way for stuff to get clogged in your cooling system.

Faulty Thermostat

A faulty thermostat will cause your car’s engine to overheat. The excessive heat causes pressure to build up within your radiator until it finally bursts. Check out our guide on how to replace a radiator thermostat for tips on removing and installing one of these components.

Which Radiators are Most at Risk from Bursting?

While every radiator is at risk of bursting, it’s true that certain designs put your radiator more at risk than others.

For example, pressure relief valves are designed to safely release extra pressure from radiators, but many drivers have found themselves on the wrong end of a burst radiator because they didn’t realize there was an issue with their vehicle and failed to check for telltale signs of an approaching leak.

What to do if Your Radiator Has Burst?

If your car radiator has burst, you’ll want to move it out of traffic and call for assistance. While you’re waiting, turn off your engine, remove any luggage or objects blocking your radiator, and open any windows if possible.

To prevent further damage and potential injury you should also raise your hood to avoid a buildup of heat inside your vehicle.

How to Avoid the Radiator Bursting?

The radiator is one of your car’s most important components because it’s what keeps coolant flowing through your engine block and into your car’s heater.

It doesn’t take much damage for things to start going wrong so it’s important that you do everything you can to keep your vehicle running properly. If you notice any signs of damage, such as overheating or coolant leaks, get it checked out right away.


Although radiators are often thought of as safe and reliable, they can still burst. To avoid having your radiator explode while you’re driving, stay away from substances that could potentially damage it.

Coffee is too acidic for your radiator, especially if you’re drinking several cups on a daily basis. Be sure to keep citrus fruits out of your car (and your trunk). And, whatever you do, never try to repair a busted radiator with duct tape!