How to Deal With Air in Heater Core?

If you ever notice a gurgling sound from under the dashboard of your car every time you run? It could be a sign of blocked air bubble in the heater core of your cooling system. If you have tried several times but still not be able to unclog the heater core, reading all useful information in this article will help you.

In general, airlock does not allow a heater system to work normally, thereby leading to overcooling. During the winter season, this is a common problem when a heating system in your car depends on coolant. What you just need to do is bleeding it out in a suitable way.​

What Does Air in Heater Core Mean?

Whenever you open a coolant system during leakage or repair, the air is highly likely to replace the coolant. As a result, air would be locked in the heater core of a cooling system and prevent hot coolant from coming into the heater core. There are five possible reasons why this problem happens:

  • Bad radiator cap.
  • Leakage in the control valve.
  • Lack of attention and care when refilling coolant.
  • Possible leakage in hosepipes.
  • Blown-up head gasket.

The air in heater core would eventually oxidize the coolant, which leads to corrosion over time. As a result, it will eat away and perforate the aluminum layer of the heater core. Therefore, it is really important to keep your system air-free so that you can operate your car safely.

Recommended for You: 

How to Remove Airlock from The Heater Core​?

To remove air from a heater core, you need the following tools: eye mask, protective gear, and device to jack the car.

The first thing you need to do is fixing the causes of the problem that have been mentioned earlier. Otherwise, it might keep recurring in the future. The following are some easy methods for you to deal with this problem:​

Method 1: Burp the coolant system

For many people, this method is quite similar to the way we bring our kid to bed after hearing his burp. If you are living in any areas near a mountain, take out your car for a mountain driving and then park it on a slope or an inclined ground. If not, jack the car so that its front portion is in a higher position compared to the trunk. You should do the following steps:


  • Find a coolant bottle.
  • Slowly remove the cap of the radiator and some coolant to make sure that it doesn’t bubble up.
  • Run the engine and let it warm up for a while.
  • After reaching the operation temperature, the valve of heater will automatically let the coolant flow into the heater core, which pushes out all air bubbles.
  • Stop the car from 15 to 30 minutes.
  • Keep a look on the level of coolant in radiator. You would notice burping and bubbling action by the coolant frequently. After this action disappears, slowly put the coolant.
  • After abound 20 minutes, you would see a constant coolant flow without any burps or bubbles.
  • Close the cap of the radiator.

Method 2: Apply radiator pressure tester

This method can by used for small issue with the airlock.

  • Run the engine and then let it reach the operation temperature.
  • Loosen the outlet clamp of the heater core.
  • Use radiator pressure tester to pressurize the radiator.
  • You would see the flowing of coolant from the loosened hosepipe. After the bubbling sound subsides, tighten the clamp.
  • Check for the amount of coolant in the radiator and then fill it accordingly.

Method 3: Use a combination of water and antifreeze

    • Fill up the radiator with the mixture of 30 percent distilled water and 70 percent antifreeze. You could use a tester to check the level of antifreeze.
    • Apply the allen wrench on the hosepipe. When you see bubbling water, loosen the wrench to allow the bubble come out.
    • Continue to add the mixture till all of the bubbles have disappeared and you notice a constant mixture flow in the heater core.

This method is actually similar to method 2. But it will depend on the needed tools that you are carrying.

Method 4: Set up flush kit

  • Go to any accessory shops and find flush kit fixture, which is made with a garden hosepipe connection, then install it in the heater hosepipe’s outlet.
  • Open the garden hosepipe connection’s cap and fill up the radiator with coolant.
  • Once the coolant has flown out of the fixture, immediately shut the opening garden hosepipe. The coolant flow during the opening will make sure to carry away all air bubbles.
  • Check for the coolant amount and secure the cap of the radiator.


In most situation, an airlock in the heater core always means that there would be potential problems (non-serious or serious) with your vehicle in the future. Therefore, you can keep many issues from occurring by paying special attention to it. The simple methods and useful tips mentioned above to solve the problem with the airlock in a heat core on your own. You do not have to look for any automobile mechanic when you do it effectively. Now drive your lovely car on the road without any noisy sounds. After all, it is an essential part of your family and also needs thorough maintenance and care as well.


What If Your Vehicle Smells Like Burning Rubber?

How to Deal With Problems in PT Cruiser Transmission?


1 thought on “How to Deal With Air in Heater Core?”

  1. Would an exhaust smell be coming from the heater core.Exhaust system seems ok. It happens with the a/c and heat (this happens occasionally)


Leave a Comment

Your Auto Space