It happens to many of us sooner or later: during a routine checkup, your doctor says they believe your stomach pains are due to a clogged radiator.

No, wait — sorry. We got this article confused with a “So You’ve Been Eating Too Much Red Meat” article we’ve been meaning to write.

It’s highly unlikely that a clogged radiator will make your stomach hurt — but it can put a serious hurting on how well your car functions. Below, we’ll reveal the signs that you might have a clogged radiator, as well as show you exactly what you need to do to remedy the situation.

What Does Your Radiator Do, Anyway?

If you’ve ever spent time inside a car’s engine, then you know two things to be true: Wayne Szalinksi has his shrink-ray working again, and it gets really hot in there.

All that heat can cause the components to become overheated and damaged, which is why your car pumps coolant through the engine. This keeps everything in nice working order, but it creates another problem: it makes the coolant incredibly hot.

The radiator is designed to solve this problem. It disperses the fluid, making it easier to cool, and exposes it to the outside air, dissipating the heat.

Once the fluid is cool, it’s sent back to the engine to resume its job chilling everything out in there.

How Do Radiators Become Clogged?

Now that you know how a radiator works, you can understand how a clog can really gum up the works. After all, if the fluid can’t circulate easily, the heated coolant will be stuck inside the engine block, where it will likely do more harm than good.

But how did the radiator get clogged in the first place? Was it something you did? Seriously, what did you do???

The answer most likely is that you neglected to change your coolant, or you left your car sitting in one place for too long.

A car engine is a filthy place. It’s full of dirt, gunk, grime, rust, and a bunch of other stuff that you don’t want to know about.

Some of that sediment will eventually make its way inside your radiator fluid, and over time, more and more gunk will accumulate. This can lead to a clog, especially if you’ve let the coolant get old or let it sit too long.

6 Signs You Might Have a Clogged Radiator

If a clog forms inside your radiator, you’ll notice that your car will start to malfunction in a few different ways. You might notice all or just a few of these, but the important thing is not to ignore any of them.

1. Your Car Begins Overheating

If there’s a clog that prevents your coolant from circulating properly, it’s not surprising that your car would start to run hot. The coolant will be unable to move freely through the radiator or engine block, and that prevents it from dissipating the heat.

As a result, things will start to get quite toasty underneath your hood, and your thermostat (or possibly your check engine light) will be your first sign that something is wrong.

2. The Internal Heating Starts to Go

While things are getting hot in the engine, the inside of the car might be quite cold. That’s because when you turn on your car’s heater, it draws much of that hot air from the engine.

If your radiator is clogged, though, it could interfere with the entire heater core, cutting down on the amount of warm air that comes out of your vents.

To make matters worse, this warm air will build up inside your engine, causing it to overheat even more.

3. You Notice Coolant Leaks

If the radiator fluid gets stuck inside the radiator, the fins can start to become corroded. This could then lead to coolant leaks.

If you notice fluid pooling under your car if it’s been parked for awhile, you should get it checked out immediately. Even if your radiator isn’t clogged, it could still be damaged, and that shouldn’t be ignored.

4. You Notice Gunk in the Reservoir

This is a pretty clear-cut sign that you might have a problem on your hands, and it usually accompanies a coolant leak.

If the clog has been causing a leak, your car will probably alert you to the fact that your radiator fluid levels are low. Anytime you have to refill the reservoir, take a moment to inspect the fluid that’s already in there.

If it’s full of sediment or other junk, that means your fluid is on its last legs. It might not have caused a clog yet, but it’s only a matter of time until it does

Fun fact: the horror that a car owner feels when they see sediment in their radiator fluid tank was the inspiration for the hit 1992 film, Reservoir Clogs (we’re so sorry).

5. Your Water Pump Goes Out

As mentioned above, clogged radiators are often due to a buildup of sludge and sediment inside your radiator fluid. That gunk can do more than just jam up your radiator, however.

It can also damage the water pump, as the fluid that travels to the pump will be contaminated and lack its usual anti-corrosive and lubricating qualities.

It’s important to note that this nasty fluid can damage the water pump even before it clogs the radiator, so if your pump goes out, you should take a long, hard look at the condition of your coolant.

6. Your Head Gaskets Become Damaged

A clogged radiator can damage more than just your water pump. In fact, it can bring harm to parts that have nothing to do with the cooling system at all.

The head gaskets are especially vulnerable to heat damage, so if the clogged radiator causes your engine to overheat, they could start to leak or even break. Your cylinder head could crack as well, and that’s not a cheap repair by any means.

How to Fix a Clogged Radiator (Or How Much It Will Cost to Have Someone Else Fix It for You)

If you’ve noticed any of the signs above, it’s time to take action. Fixing a clogged radiator is relatively cheap and easy — and it’s certainly cheaper and easier than waiting for something to go seriously wrong due to your engine overheating.

The process is called “flushing your radiator,” which is a term you may have heard and pretended to understand before. It basically means that you’ll need to drain the existing coolant, pour some cleaning fluid in the system, and then add new coolant.

As we said, this is a fairly easy procedure, but it still requires some know-how. If you don’t even know where your radiator is or what it looks like, you may be better off leaving it to the pros.

Then again, if you’ve always wanted to learn how to do your own car maintenance, this is a good starter project.

How to Flush Your Radiator

Before you begin, you’ll need to assemble a few tools:

• A funnel
• Gloves
• A drain pan
• Wrench or ratchet
• Soap and water

You’ll want to park your car on a level surface and block the wheels so that it doesn’t roll at an inopportune time. We recommend jacking the vehicle off the ground to make things easier, but that’s not completely necessary.

Also, make sure the car has been off for a few hours. Coolant is designed to wick away heat from the engine, after all, so it’s going to be hot when it comes out — and if it comes in contact with your skin, you’re going to think it should be called “burnant” instead (again, we’re so, so sorry).

1. Clean the Radiator

You should start by scrubbing the radiator with soap and water, paying special attention to the area around the radiator cap.

Make sure to get all the dirt and grime that you see; the idea is to make sure that you don’t accidentally knock gunk into the radiator once you’ve flushed it, thus defeating the purpose of doing it in the first place.

2. Inspect the Radiator While You’re There

Once you’ve got your radiator nice and shiny, you’ll be in prime position to check it out and make sure it’s not cracked or damaged in any way. Be on the lookout for rust and corrosion as well, and see if the hoses are damaged.

If your radiator is broken, you’ll need to replace it before you continue, as any coolant you pour in will just leak out anyway.

3. Put the Drain Pan Under the Radiator

You’ll need to catch all that old radiator fluid as it drains out; for one thing, dumping it is illegal in many places, and for another, it’s poisonous to animals.

You’ll also need to take the fluid to a proper waste disposal site when you’re done, and keeping it in a drain pan will make it easier to transport.

4. Drain the Radiator

There’s a drainage valve at the bottom of the radiator with a bolt on it. Take your wrench or ratchet and open the bolt.

This will allow the fluid to drain, so you might want to wear gloves for this part, as the ethylene glycol in the antifreeze can cause skin irritation.

Once the fluid has finished draining, replace the bolt.

5. Flush the System

Refill the coolant reservoir with clean water or a special flushing fluid like this one from Prestone. Then, turn your car on and let it run for at least 15 minutes.

Running the engine will send the fluid circulating through the radiator, dislodging any caked-on sediment that didn’t drain out with the old fluid.

Turn the car off after about 15 minutes and let the engine cool. Then, repeat the drainage procedure you performed in step 4.

Remember to make sure that the drain pan is still in place before you drain the system again, and even more importantly, remember to remark, “Ooh, look at all that gunk!”

6. Refill Your Coolant

After the water or flushing fluid has drained (and after you’ve replaced the bolt on the drainage valve), use your funnel to fill the reservoir up with coolant according to the manufacturer’s specifications.

Before you do this, though, you should realize that some antifreeze, like this offering from Peak, comes pre-diluted. Other antifreeze is sold in a concentrated form, and it needs to be mixed with distilled water in a 1:1 ratio.

Once you’ve filled the radiator up again, leave the cap off the reservoir and run your car for 15 minutes with the heater turned all the way up. This removes any air pockets that might have formed inside the system.

After the 15 minutes are up, turn the car off, replace the radiator cap, and pat yourself on the back. Congratulations — you just flushed your radiator!

Can’t I Just Pay Someone to Do It for Me?

Flushing your coolant is fairly easy, but it’s a messy job that can take a few hours. If you’d prefer to just pay someone to do it for you, it will most likely cost between $100 and $150.

However, in addition to paying for a mechanic’s labor and expertise, that money will also cover the cost of the antifreeze and the flushing fluid, plus the expense of disposing of all the waste.

Can You Drive With a Clogged Radiator?

If you suspect your radiator might be clogged, you shouldn’t drive your car anymore than is absolutely necessary. We’d recommend driving straight to your mechanic’s shop, unless you’re going to flush the system yourself.

As we’ve already seen, a clogged radiator can cause your car to overheat, the gaskets to blow, and even the cylinder head to crack, all of which will be considerably more expensive than a simple coolant flush.

How to Prevent Your Radiator From Becoming Clogged in the Future

If you don’t want to run the risk of having a clogged radiator in the future, then the best way to avoid it is by having your coolant system flushed and the fluid replaced regularly.

Luckily, this shouldn’t be too much of a hassle, as it’s only recommended to flush your radiator every 5 years or 100,000 miles.

Also, don’t leave your car sitting for too long without running it, as that can allow all that sediment to pool and rust inside the radiator. This can cause a clog the next time you fire up the engine.

Final Thoughts

Whether it’s in your toilet or your radiator, a clog is never a good thing. A clog in your radiator can cause your engine to overheat, as well as potentially damaging any number of the parts inside.

Fortunately, clearing out a radiator clog is both cheap and easy, so as long as you catch it in time, it shouldn’t be too much of a problem.

The same can’t be said about the clog in your toilet, however. That’s one problem you can’t flush your way out of.