What Should You Do When There’s Foam In Radiator?

So, you allow the car to cool off for some time due to overheating. Moreover, you even take out the cap of the radiator to ensure the flow of water. But, instead of seeing a water flow, you’re now seeing white foam in radiator.

What could’ve caused this issue? And what should you do when there’s foam in radiator?

Well, leftover chemicals and airlocks can cause foaming in the radiator. And yes, the foaming of the radiator is an issue. But you shouldn’t worry as we’re here for you. In fact, we’ve even shown ways of fixing this issue in this article.

foam in radiator

Moreover, we’ve discussed what leads to this problem in the first place. We’ve also instructed on what you should be doing to tackle this situation. Furthermore, there’s also an FAQ session in the end that’ll clear off most of your confusion about this problem.

So, what are you waiting for? Let’s jump right in.

What Causes Foam in Radiator Reservoir?

So, how can you identify the factors behind the foaming of the radiator? Is it the engine oil or is it a bad head gasket? Whatever the case is, if you have knowledge about the factors, you can take early precautions.

So, without further ado, let’s look at some of the factors that contribute to this problem:

● Cooling System Corrosion

At times, if you have a bad concentration of coolant with the corrosion, it can cause a problem in the radiator. This means if you add in a new coolant, it’ll still mix along the corrosions of the cooling system.

Hence, you need to make sure that you flush the system a lot of times until you see clear water. Otherwise, no matter how much new coolant you put in, it’ll still mix with the corrosion. And this will cause foam in radiator coolant.

● Worn Out Chemicals

When you purchase a coolant from the market, you’ll notice that it has an “anti-foaming” property in them. But still, why does it lead to foaming of the radiator?

Well, if the chemicals are worn out, they won’t work properly. Similarly, if the coolant’s foaming particles are worn out, it’ll contribute tofoam in radiator water.

● Less Concentrated Coolants

Yes, you heard it right. It’s important to have a good concentration of the coolant. But why is it so?

If you have less concentrated coolants, they’ll boil the water. As a result, the boiling of water will cause bubbles to form. This will eventually lead tofoaminess in the radiator.

● A Blown Up Head Gasket

Around 40% of the time, a blown-up head gasket is taken to be the main culprit of foams inside the radiator. If your gasket is blown up, it’ll cause a lot of problems. It can cause the leakage of gasses inside the coolant system as well.

To replace a gasket is an expensive option to look into. But, if that’s the issue, you’ll have to eventually change or repair it.

● Leakage Of Combustion Gas

Yes, it’s true that combustion gasses too can leak into the coolant system. This can also cause the forms inside the radiator. But how can you be sure if leakage is happening?

You can identify whether the leakage is happening in the radiator by the following steps.

1. Start the engine. But, make sure it’s cold and not heated before.

2. Remove the fan-belt of the engine. Also, make sure it isn’t wrapped with a crank pulley.

3. After this, remove the radiator cap.

4. Add in water and make sure that the amount is enough.

5. Make sure that the amount of water you’re putting in is causing it to reach the surface.

6. Now, throttle the engine several times. At this time, keep an eye out on the water of the radiator.

7. Watch the radiator’s top. If the water on the top has bubbles forming on them, it means combustion gas is leaking.

8. As you’ve removed the fan-belt before, the only way bubbles can form is through a combustion leak.

Apart from this, make sure that you’ve removed the thermostat of the upper hose before starting this test. Not all cars have a thermostat in them, but if your car has one, remove it.

● Other Factors

By now, you’ve known head gaskets and worn out chemicals to be the main reasons behind the foaming of the radiator. But wait, let me tell you something.

Sometimes, even airlocks and old antifreeze can cause foams to build up in the radiator. If someone puts washer fluid in the reservoir of the anti-freeze, it also causes white foams.

Many times, people don’t even realize these factors and change up other factors that don’t contribute.

On the other hand, even if you have a bad radiator, it can still cause your radiator to foam. How is it you may ask?

Well, a bad radiator cap means it’ll allow air to pass inside your radiator. As a result, the air getting inside will cause foam in radiator overflow

The Fixing Guide

So, you’ve known all the factors that lead to the foaming of the radiator by now. But, don’t worry. Just because your radiator has foams and bubbles in them, it’s not the end of the world.

In fact, you can fix this issue quite easily with some simple methods. That being said, let’s look at what preparations you’ll need before solving this issue.


Yes, you’ll require some tools for the job. However, all of these tools are available and affordable. So, you can purchase them online or from the local shops at a convenient price. Let’s take a look:

After you’re done managing the tools, let’s look at the simple methods that we’ve prepared for you:

Method 1: Blown Up Gasket Repair

As you might already know, around 40% of the time, a blown-up gasket causes the foams inside a radiator. That being said, let’s look at the steps on how you can solve this issue:

Step 1: Firstly Check the Engine Oil & Radiator Cap

Before trying to fix the issue on the gasket, check the engine oil and the radiator cap. This is because you’ll need to be sure if that upper or backward hose is causing the problem.

If you check the dipstick and there’s no moisture in them, your oil has no foam formed in them. Similarly, if you check the radiator cap and it’s dry then there’s no white foam in radiator coolant.  

Step 2: Scrape or Wipe off the Impurities of the Blown Part

You’ll notice inside the gasket that there are impurities like oil that have formed. These parts actually contribute to the leakage of the gas in the gasket. Even though they’ll look like rust, you can wipe those off easily.

Use a bit of cleaner and clean it. However, don’t overdo it. Also, never put any kind of bandage or other materials to wipe off the particles.

Method 2: Getting Air Out Of The Radiator

By now, you should know that if there’s air inside your radiator, it can also contribute to foams forming as well. So, it’s essential that you get all the air out of the radiator. Here’s how you can do it:

Step 1: Put the Funnel Attached to a T-shirt

Firstly, put a funnel on the radiator cap and attach a t-shirt to it. The t-shirt mainly catches all the dirt and debris.

After that, pour in fresh coolant through the funnel into the radiator cap.

Step 2: Start the Car

Following the previous step, start the engine of your car. By doing this, you’ll notice that the air is coming out of the radiators. The air comes out in the form of bubbles. So, it’ll be easy to notice that.

Step 3: Close the Cap

Lastly, the air will come out of the radiator cap. But wait, before you end the process, close off the cap tightly so that no more air enters inside the radiator.

Method 3: Clearing the Cooling Air System

The air system needs to be cleared. This is because the system gets mixed with corrosion to form foams inside the radiator. Even if you put a new coolant inside the radiator, it’ll still get mixed with the corrosion.

If you want to get rid of the foam in radiator, then pay attention.

So, let’s clear the cooling system by following the steps below:

Step 1: Start the Engine

Firstly, turn on your car by starting the engines. Keep the engines on and go to the front. You’ll see bubbles in the radiators.

Step 2: Keep the Engine On & Notice the Air Bubbles

After you keep the engine on for some time, you’ll notice the air bubbles working their way up on the radiators.

Step 3: Flush and Refill in Fresh Coolant

By pouring in fresh coolant in and out, the bubbles start to form in the radiator. Also, keep the engine on and the bubbles will eventually come out themselves.

Thus, by pouring in fresh new coolant, you’re eliminating any bit of rust or impurities in the radiator. You can also refer to this method as the radiator flush. However, make sure to check out if there’s no heat after the coolant flush.

Frequently Asked Questions

What does it mean when your coolant is foamy?

It means that your engine is hitting the combustion cycle and it’s heating up to form the coolant.

Is it worth fixing a broken gasket?

Yes, if you don’t want to replace the gasket, you can fix them.

Wrapping Up

That’s all we have for you. Hopefully, by reading this article, you’ll now know what to do when there’s foam in the radiator.

At the end of the day, make sure the radiator caps are tight and you’re not using worn-out chemicals. So, why don’t you try these methods for yourself? Good Luck.

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