How to Purge the Air from the Heater Core in your Car

When the air gets stuck in your heater core, you will have issues like a gurgling sound under your dash. Keeping it that way can cause a lot of trouble for your car in the long run. So, if you have air in your heater core, you will need to purge it as soon as possible.

Don’t know how to do it? It’s okay; I am here to help you out with that. I will go through the complete procedure of purging air from your heater core. Without wasting further time, let’s get going with it.

What causes the air in the heater core?

There are typically several causes for air to get stuck in the heater core. This doesn’t happen instantly for anything you do. It’s a continuous process that leads to the issue. Here’s what happens.

Whenever you open your car’s coolant system for any purpose, some air enters the heater core. This air gets locked inside the cooling system. Now, this issue can happen because of various reasons.

An obvious one is unaware or careless while refilling the coolant. It’s essential to pay attention to your coolant refill system and see if any air is getting locked inside or not. Aside from that, having a poor radiator cap can also cause this issue to happen.

If you have leaks inbuilt with the hoses, then that’s also a probable cause for this issue. Another primary reason to look out for is a blown-out head gasket. This can cause leaking in the coolant, which may lead to this problem.

Lastly, if you have any leak in the heater control valve, you will face this issue. Any stuck air in the coolant system can damage the whole thing over time. Issues like corrosion happen when you don’t attend to the problem as quickly as you can.

This eventually results in damaging your engine beyond repair. That means you have to spend a lot of money to get that fixed. So, you have to get rid of any air from your heater core as soon as you can to solve the problems.

Related: car overheats when AC is on

How to get rid of the air in the heater core

Now, there are various methods that you can try out to get rid of air from the heater core. Try one or the other if any of them fails. And if none of them work, then you have to opt for professional help. Also, make sure not to do overdo things by yourself without knowing what you are doing. This may permanently damage the engine.

Let’s look at the different methods you can try to get rid of air from the heater core.

Method 1 – Burp the coolant system

This is a method that works quite well for purging air from your heater core. You can do this one using the following steps –

  • First of all, you have to lift the front part of your car in some way. You can either use an area with a slope to keep the front elevated or jack it.
  • Now, get your coolant and prepare it for operation.
  • You have to remove the cap to bring out some coolant to stop it from bubbling up.
  • Then, start up the engine and let it warm up for some time. As soon as the operating temperature comes up, the coolant starts flowing through the heater core. It causes the air bubbles to push outside.
  • After that, leave your car idle for about 20 to 30 minutes.
  • Then, check up on the radiator and see the coolant level. Once the coolant stops bubbling or burping, start adding coolant slowly.
  • In the beginning, there will be some burps and bubbles, but after 20 minutes, everything should flow smoothly.
  • Finish up the process by closing the radiator cap.

Method 2 – Use pressure tester for radiator

If you have minor problems due to the airlock, this is an excellent method to follow. It’s quite easy to do with a radiator pressure tester. Here’s how you do it.

  • You have to start up the engine and get it to operating temperature.
  • Then you have the loosen the outlet clamp of the heater core.
  • Next up, starting pressurizing the radiator. This is where you will need the radiator pressure tester.
  • Now, you will see the coolant flowing through the hose. When the bubbling noise of this process starts lowering, you can start tightening the clamp.
  • Finally, check up on your radiator and see how much coolant you will need to refill.

Method 3 – Use flush kit

This is a very convenient method of purging air from your heater core. It brings simplicity to the process and makes it very easy to do. Just follow these steps-

  • Get a flush kit from an automobile store, or you can look it up online. It comes with a garden hose connection.
  • Now, take off the garden hose cap and then use the coolant you have to fill up the radiator.
  • When the coolant starts flowing through the hose, you have to close the opening of the hose. The coolant flow drives away the air bubbles stuck inside through that opening.
  • Just like the previous method, check up on your radiator for the coolant level and refill it.

Related: auto air conditioner temperature


To sum up, these methods should be enough to purge the air in the heater core. You can try out any of the methods that suit your needs. But don’t be ignorant about this issue because it can lead to some severe damage to your car engine in the future.

Also, if the methods mentioned above don’t work, you might have some other issues. In that case, opt for a professional car mechanic to look into the matter. Otherwise, the basic air stuck in the heater core problem is easily solvable at home, and anyone can do it.

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