Bubbling Sound In Car [Why + How To Fix]

Low coolant level, the air in the coolant system, and blown-out head gasket are the caveats responsible for the bubbling sound in car. 

Among them, air trapped in the coolant system is the most common reason behind the gurgling sound. Improper bleeding when replacing the coolant system is the main reason that causes the air to trap and produce gurgling noise. 

Bleeding the air from the coolant system will be an easy fix. Apart from these, you should also address other problems like blown-out head gaskets, and air in the heater core and treat them to quiet the gurgling noise. And this guide will break down the ways of stopping the bubbling noise. So, keep reading. 

Bubbling Sound In Car [Reasons + Solutions]

Don’t know what causes your car to make the gurgling noise? Then, stay in tune till the end of this chapter to know all the reasons behind a bubbling sound. 

Note: You can also read how to fix Groaning Noise when reversing.

1. Low Coolant Level

Too low a coolant level is the reason that causes your car to make a bubbling or gurgling noise. Because of the low coolant level, the coolant starts flowing back into the heater core when you start the engine. And the water pump begins circulating the coolant. 

The heater core is at the highest position compared to other components in the coolant system. If the coolant level is too low in the coolant system, it will drain the heater core first when you shut the engine off.

And it leaves a space that will refill on the restart, which produces a gurgling noise. In specific words, the void will be refilled by air and it creates an air pocket, which is responsible for the gurgling sound. 

To avoid this issue, we recommend you check the coolant level frequently. Whenever you hear the gurgling noise, inspect the coolant and refill it with fresh coolant if needed. 

2. Air In The Coolant System

Gurgling sound in-car dashboard! It’s common to hear the bubbling sound under the dashboard when there is air in the coolant system. 

Improper bleeding of the air out of the system is the main culprit behind the trapped air in the coolant system. 

You can easily avoid this problem by bleeding the air properly. Just unscrew the radiator reservoir tank. Then, connect it to your latch on the hood. Now, start squeezing the lower radiator hose to force the air through the system. Of course, you should open the bleeder valves to let the air bleed out. 

3. Head Gasket Gets Blown Out

Bubbling indicates the air pressure is building in the coolant system. And a blown-out head gasket is the caveat that causes this issue.

When the head gasket gets leaked, the coolant will make its way into one or more cylinders in the engine. But the heck is- you can’t see the leak as the coolant gets already burned off.

The cylinders then force the air back through the head gasket into the coolant system and air makes its way up to the overflow tank where the bubbling sound produces. 

Either repairing or replacing the blown-out head gasket is the only solution to stop the bubbling sound. You don’t need to spend a fortune to repair or seal the leaky head gasket.

What you need to do is- just pour a sealant into the radiator and run your engine at idle for half an hour. We recommend you watch the below video to know how to do it correctly. 

Alternatively, you can replace the blown-out head gasket to solve the issue permanently. And it will cost you over $1000 to fix the problem. 

4. Air Gets Trapped In The Heater Core

Coolant generally makes its way through the heater core when you run the engine. If the air gets trapped in the heater core, it will create a bubbling or gurgling sound.

Either way, excessive amounts of antifreeze circulating through the heater core can cause a bubbling noise.

If the noise is from the air trapped in the heater core, we recommend you bleed the system. Otherwise, you should drain out the excess coolant from the system and fill it according to the suggested level.  

5. It’s Normal

Most often it could be a ‘no-problem’ situation. It’s pretty normal when you shut the engine off, for the compressed coolant & gasses in the AC to continue squeezing through the expansion valve.

In short, hearing the bubbling noise from some cars that have expansion tanks as part of the cooling system is normal. 


How do I fix bubbling coolant?

A faulty radiator cap can also cause a bubbling noise. You can easily overcome this issue by replacing the bad radiator cap. First off, flush away all the coolant from the system and replace the radiator cap. Then, drive your car for half an hour, which will stop the bubbling. 

What are the signs of a blown head gasket?

You can observe the following signs if the head gasket gets blown out: 
1. Bubbles up coming out of the radiator and the coolant tank
2. Keep losing coolant without any leaks.
3. Engine gets overheated 
4. The tailpipe will release white smoke

Can a bad water pump cause bubbles in the radiator?

Yes, a bad or failed water pump can also cause bubbles in the radiator. When the water pump seal gets damaged, it allows the air to enter the water pump. It causes bubbling when the air gets into the inlet neck. To avoid this issue, just fix the water pump seal or replace the water pump itself if it gets leaked. 

Can I drive with a blown head gasket?

Technically, you can drive your car with a blown head gasket. But you can’t run the engine quite long. It will cause the coolant to leak and the engine gets overheated. If you drive the car for a long time, it will cause further damage to your engine. You can fix the blown head gasket by pouring a sealant like K-seal into the radiator.


As the air in the coolant system is the main culprit, we recommend you start with bleeding the air out of the system.  

Then, treat the other issues we mentioned. If you fail to stop the gurgling noise after trying out all the possible ways we described, it’s time to bring your car to a professional. 

Otherwise, you may fall into big trouble, which will cause you to spend a fortune to fix the issue. 

About John M

John contributed as a technical head at an automobile company just 2 years after his post-graduation in Automobile Engineering. He loves to lead a free life, so he left his job & started blogging. Now, he does research on every automotive problem, part & product and seeks a better solution & best products & shares his findings with his readers to help them as well as to minimize their struggle.

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