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How Do I Get Rid Of The Air In Heater Core?

Getting a gurgling noise from under your dash each time you start your car? You have probably got an air bubble locked in the heater core of the cooling system. Have you tried several possibilities but still not been able to get rid of the air in the heater core? These simple tricks will help you out.

Airlocks do not allow your heater system to work, thus resulting in overcooling. This is a major problem during winter when the heating system works on the coolant. Air getting locked into your heater core is a very common scenario. You just have to bleed it out the right way.

How Does an Air Lock Happen?


There is a chance of air displacing the coolant whenever you open the car’s coolant system during a repair or leakage. Thus, the air gets locked in the heater core of the cooling system. This airlock prevents the hot coolant from reaching the heater core.

The following are the possible reasons, why air gets locked inside the heater core:

  • Lack of care and attention during coolant refill
  • Poor radiator cap
  • ​Inbuilt leaks in hoses
  • ​Head gasket being blown up
  • Leaks in the control valve of the heater

The air in the heater core causes oxidation of the coolant. Hence, makes it very corrosive over time. This eventually eats away the aluminum surface of the heater core, thus causing perforations in it. Therefore, keeping your system air-free is very important for the safe operation of your car.

How to Bleed Air from Heater Core?

Here are some tricks to get rid of the air in the heater core of your car.

  • What you need: Protective gear, eye mask, and tools to jack your car.
  • Skills required: Basic skills such as starting your car, jacking it up, pouring coolant, and cleaning the mess are required.
  • Heads up: You might be subjected to second-degree burns, as you are going to handle hot coolant. Hence, using protective gear is highly recommended. Also, dispose of the coolant properly on the ground. Do not allow kids or pets to be near you when you are going to perform the below actions.

To get rid of the airlock from the heater core, you need first to fix the issue that caused this problem. The reasons mentioned above could have been a reason for causing an air bubble. Hence, we recommend you to solve that first. If you leave the airlock unattended, the problem may keep recurring.

Method 1: Burping the Coolant System

The analogy of this method is similar to how we put the child to sleep after hearing its burp. If you live in San Francisco or somewhere near the mountains, take your car out for a mountain drive. Park it in an inclined manner on a slope. If you do not have this facility, jack your car such that the front portion of it is elevated compared to its trunk. Follow the below steps:

  • Get your coolant bottle and have it ready.
  • Remove the radiator’s cap slowly and remove some coolant, so that it does not bubble up.
  • ​Start the engine of your car and allow it to warm up for a while.
  • ​Once it reaches the operating temperature, the heater valve automatically allows the coolant to flow through the heater core. This action pushes the air bubble outside.
  • ​Leave the car idle in this state for 15-30 minutes.
  • ​Keep a watch on the coolant level in the radiator. You will be able to see bubbling and burping action by the coolant occasionally. Slowly add the coolant once you find that the bubbling action has subsided.
  • ​After around 20 minutes, you should see a steady flow of coolant without any bubbles or burps.
  • Close the radiator cap.

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Method 2: Using Radiator Pressure Tester

This is another method, which works best for minor issues of the air lock.

  • Start the engine and allow it to reach the operating temperature.
  • Loosen the heater core’s outlet clamp.
  • ​Pressurize the radiator by using a Radiator Pressure Tester.
  • ​You can see that the coolant will start flowing from the loosened hose. Tighten the clamp at this point after the bubbling noise subsides.
  • Check the radiator for coolant level and fill it appropriately.

Method 3: Installing Flush Kit

air in heater core

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This method includes the following steps.

  • Install one of the flush kit fixtures, which are available in motorcycle accessory stores, in the outlet of the heater hose. This fixture has a garden hose connection.
  • Open the cap of the garden hose connection and fill the radiator with coolant.
  • ​As soon as the coolant flows out of the fixture, close the garden hose opening. The flowing of coolant through this opening ensures that the air bubble has been carried away.
  • Check for coolant level and secure the radiator cap.

Method 4: Use of Antifreeze and Water Mixture

If you have the Factory Service Manual (FSM) for your car with you, this method would be suggested in that.

  • Fill the radiator with a mixture of 70% antifreeze and 30% distilled water. You can use a tester available on the market to test the concentration of antifreeze in the mixture.
  • Use an Allen Wrench around the hose. As you see water bubbling up, loosen the wrench to let out the bubble.
  • Keep adding the mixture until all the bubbles have subsided and you see a continuous flow of the mixture through the heater core.

This method is similar to Method 1 in a way. But it depends on the necessary items which you carry.


Air in the heater core also indicates that there are possible serious or non-serious issues that may occur with your car in the future. Therefore, looking into it at the right time can prevent many problems from occurring. The above methods enable you to look after the issue of the airlock inside the heater core all by yourself.

Isn’t it simple? You need not run looking for a car mechanic when you can easily do it yourself. Now get your lovely lady on the streets without any noise; after all, she is a part of your family and needs utmost care and maintenance.