How to Flush a Heater Core the Right Way

During the cold winter days, your car's heater is an essential in keeping you warm while driving! Like your vehicle's air conditioning system, it improves the comfort while you're on road trips or on your way to work. But what exactly does your car's heater have that makes its power up efficiently? That's where your car's heater core comes along. If ever your vehicle's heater isn't working as well as it usually does, then it may be time to check the core to flush it out.

But what does flushing mean? Read on as we show you what you need to know about your heater, as well as how to flush a heater core.


What is a Heater Core?

A heater core is part of your car's cooling system, a small radiator that dispenses heat. It keeps your heater and defroster working by circulating coolants throughout the little tubes it has.

The heater core is behind the dashboard on the passenger's side, housed and buried under everything else to keep it protected and working.

Heater Core

Photo by Autohausaz

The heater core works by using water and an antifreeze mixture, which then uses engine heat to distribute the warmth into the atmosphere. The heater core collects this warmth and gives some of that heat into the cabin, forcing air through the vents of your air conditioning system.

You'll be able to control it through the thermostat, controlling the valve or the doors of the heater core. You can even have dual climate functions where the driver and passenger have different temperatures for comfort.

Why Flush Your Heater Core

It's important to flush your heater core to enjoy your heater and appropriately defrost the inside of your car. That way, you and your passengers are comfortable and will be able to ride without feeling freezing, especially during cold weather.

Flushing your heater core is relatively easy, though you may need a friend for help if you are a beginner. It saves money instead of using a mechanic, only taking an hour or so of your time.

How to Know When to Flush Your Heater Core

Before you know how to flush a heater core, you will need to know when it needs flushing first. Here are the telltale signs you need to unclog it:

Vehicle Fogs

If your vehicle fogs up with condensed windows, then your heater might have a leak which spills hot vapor into your vehicle.

Heater core

Sticky and Sweet Smell

If your radiator fluid is leaking coolants, then it would smell sweet and humid. You can smell it in the cabin of your car, or underneath.

More Coolant

If your vehicle needs more coolant and radiator fluid, then it may be from your heater core leaking. The passenger side may incur moisture so that you can check that out as well.

Dead Heater

A telltale sign of your heater core not working is if it gets colder in your car and the heater doesn't properly function. You will need to check for other signs to know if the core is leaking.

Overheated Cooling System

If your engine is overheating while the air conditioning system distributes cold air into the cabin, then it's a serious condition that can either be through the fault of your heater core or other components in your car.

If you feel like your car is overheating, then have it checked immediately.

What You Need to Flush Your Heater Core

To flush your heater core, you will need to prepare the following materials:

  • Barb Fitting Adapter
  • Bucket
  • Clear Tubes
  • Garden Hose ⁃
  • Safety Gloves and Glasses ⁃
  • Pliers ⁃
  • Rags

When purchasing a hose, make sure you know the size your hose needs to be when adding coolant into the heater core. You can find information from your vehicle's repair guide, or from trusted sources online and friends who are knowledgeable about cars.

Heater Core

How to Flush a Heater Core

To flush your heater core completely and have it running regularly again, here are the steps you'll need to follow:

Heater Core

1. Prepare the AdapterScrew the adapter and attach it to the tubing to reverse the direction of your heater core's fluid flow. This removes any sediment that may cause the problem.

2. Check for Heater Core HosesYou can find these two thick hoses near the firewall, a metal wall found inside the vehicle and engine area. Look at the passenger's side, where the heater core is located.Look for the inlet and outlet hoses, identifying which is which. The inlet hose is warmer than the latter (if the engine is hot).

3. Prepare EngineWhen flushing your heater core, make sure that the engine isn't cold, since it is dangerous dealing with hot coolant.

4. Remove HosesUsing your pliers, pull the clamps back. You can spray silicone lubricant if it's hard to pull them out.Twist the hose to remove it. Do not damage the outlet port and prepare rags in a case of spillage.

5. Attach Garden HoseAttach the garden hoses to both ports (garden hose on the outlet and drain pipe on the inlet) and make sure there is a bucket to collect any spilled coolants and sediments.

6. Flush Out Heater CoreTurn the water on, but not completely. Keep on flushing the heater core until the water that comes out of it is clear. After, begin draining the heater core by interchanging the pipes to the inlet and outlet. Turn the water on again and flush.If the clog still isn't fixed after a few flushes, then radiator cleaner is needed. If it needs cleaning, pour radiator cleaner inside the heater core and leave it for half an hour. Flush with water again to rinse any radiator cleaner out.

7. Assemble Back TogetherDisconnect the Tubes and reconnect the hoses of your vehicle's heater core. Using the pliers, secure the clamps of your hoses and clean any spilled antifreeze and coolant.

Check your heater through testing the vehicle with a short test drive. You will know the heater core has been successfully flushed if there is warm air coming out after using the heater.It's best to regularly flush your heating core to avoid any problems with warmth and condensation in your car. If ever the problem persists, then you may need to take it to the mechanic for further assistance.

In Conclusion

Heater cores are an important part of your car's cooling system, as you won't be able to enjoy warmth without it! That's why it's important to know how to flush a heater core to prevent it from breaking down during the cold season.

My aim is to make sure this article informs you the importance of your heater core and how to flush it out in times of trouble. If you feel like your heater core shows signs of trouble, follow this procedure and enjoy the functions of your heater properly today!

So if you have any questions or have any more tips about how to flush a heater core, then please post your thoughts down at the comment session. Your opinions will be very much appreciated!

Tom Nguyen

I’m Tom, and I’m avid fan of automobiles! I love cars and learning more about how to tweak and repair them to make them look and perform better. Through a lot of projects and research, I make it a point to share my knowledge to other car enthusiasts like me.

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