Coolant Boiling In The Car: What To Do? (Explained!)

Many people have experienced this problem. Some people might not have experienced this yet, but as early as now, car owners must know what to do if your coolant is boiling inside your vehicle. There can be a lot of possible reasons why the coolant of your vehicle is boiling. 

So what do you have to do if your coolant is boiling in your car? There are plenty of reasons why your coolant is boiling in your vehicle. With that, the first thing that you should do is to determine the cause why your coolant is boiling in your vehicle. 

Your radiator can be clogged, your coolant to water ratio might not be balanced, your engine fans might not be working, you might have a blown head gasket, you might have trapped air, or you might have a faulty radiator cap. There can be many reasons. 

Each reason must be checked and diagnosed if it is the reason why your coolant is boiling. You can do the elimination method. List down all the possible reasons and then check one by one and see if it is the problem. 

And so this article is made to discuss these possible reasons. We will also be talking about what to do if your coolant is boiling. Let us start.

Coolant Boiling In The Car

Why Is My Coolant Boiling?

There are many reasons why your coolant is boiling. But the principal reason is that you have a blown head gasket. The air pressure inside your cylinder heads will be transferred to the cooling system. 

The escaped air will cause bubbles and boiling in your coolant or antifreeze reservoir. Some people would also mistake the bubbles for boiling. 

Is It Normal For Your Coolant To Boil?

No. The bubbles or the boiling is not normal for your coolant. It is terrible for your vehicle if your coolant is boiling. 

If you have boiling coolant, it is essential to know what the problem is. This can cause overheating of your engine. You can also have a blown head gasket. 

You need to take a look at your engine temperature gauge to see if your coolant is boiling. You can diagnose your car by checking it thoroughly. 

What To Do When Your Coolant Is Boiling?

If your coolant is boiling, you should immediately find the cause so that you can immediately fix it. The water will be cooled down if it passes into the radiator. The radiator will be fed with air, and it will be driven by a belt attached to an engine. 

If the water is boiling, this means that there is a problem in the system. It can also simply mean that the water level is too low and will require topping up on occasion. The fan belt can also be broken. 

You need to check if it is loose and it is slipping. The water pump can also have a blown seal. It might be leaking water too. 

You need to find out first what is the reason why your coolant is boiling. If you have to find the cause, have it fixed based on why it is broken. 

How Do I Stop My Coolant From Boiling?

The first thing you need to do is that you have to know why the coolant is boiling. Suppose you have already found out why you can now replace the part where the problem is. You need to make sure that the other sections are also diagnosed. 

You can stop your coolant from boiling if you already know the cause of it. The average cost for a head gasket can be around $500 to $850. The repair cost is why many people sell their cars instead of fixing them. 

So the only way to fix your coolant from boiling is to know the reason why. There are many possible reasons why your coolant is boiling. If the reason is a blown head gasket, you can repair it and have it replaced. 

Why Is My Coolant Boiling But The Car Not Overheating?

It is not normal to find bubbles on your coolant or if your coolant is overheating. Even if your engine is not overheating with all the boiling coolant, it is still not normal. 

And the issue here is not that your engine is not overheating; it can be that your engine is not overeating. It’s just a matter of time when your engine starts to overheat. The 

Coolant Boiling After Car Turned Off: What To Do?

Some people would do this. They would buy the replacement cap. They will wait for their vehicle to cool off and replace the oil cap with a new one. 

They will also top off the coolant. Some people would save themselves all the trouble and consult an expert. They would bring their vehicle to a mechanic. 

What Are The Symptoms Of Boiling Coolant?

You can experience some overheating. There will also be bubbles in your coolant or your antifreeze reservoir. Check also for white smokes that will come out of the exhaust. 

There can also be billowing steam that would come under the bonnet. If you find these things, check your vehicle. 

Can You Hear Coolant Boiling?

The bubbling or the coolant boiling can mean that there is air pressure inside the coolant building. A blown head gasket can cause this. 

As mentioned, a blown head gasket is the most common reason why your coolant is boiling. The coolant leaks can be in one or more cylinders in the engine. It can also be burned off. 

The compression from the cylinder will force the air back into the head gasket of the coolant system. The air will then make its way to the overflow tank, and this is where you can hear the bubble or the boiling, and you can even see some foam at the top of the coolant. 


In summary, coolant fluid must remain in good condition to benefit your engine like it should be given. Some people experience that their coolant is boiling. 

A lot of things can cause the boiling coolant. You have to know the sole cause of the boiling to know how to fix it.



Image credits – Canva

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My name is Hank, and I've been in the automotive industry for 27 years. I've been working in my own auto repair shop for the last 13 years, and now I want to help you here, on my blog. Let me know if you have any questions. Read more