How To Tell If Your Heater Core Is Bad Or Clogged?

The heater core is part of a cooling system for a car. It appears and works like a smaller version of a radiator, which circulates through the little tubes and radiates heat into the cabin. It also ensures the proper functioning of the defroster and is connected to the air conditioning system that is organized in a similar way.

When the motor of a car warms up during operation, heat is absorbed and circulated by the antifreeze/coolant, which cools it under the boiling point through and through the radiator heat sink. When it goes bad, it can cause a lot of trouble. Learn about how to tell if your heater core is bad or clogged in this article.

How Do A Heater Core Functions?

The core heater is only a smaller version of the heater, but it uses the heat from that coolant in order to warm the interior of the automobile rather than being used to perform engine cooling duty. Essentially, coolant is discharged from the rest of the cooling system.

The heat is activated within the vehicle via a valve opened to allow hot coolant to flow into the heater core (for some vehicles), or by the hot heater core, a door is opened. Typically, the coolant at about 200 degrees can provide your feet or the misty windshield with large amounts of heat. By means of blend doors that mix outside air with hot air, the systems moderate the temperatures.

If you do know how to turn on a heater inside the car, you check our article which describes it in detail.

How To Tell If Your Heater Core Is Bad Or Clogged?

While the heater core is a basic mechanism, major difficulties may arise if it is not. The location of the element, which is normally behind the dashboard, can also mean a very pricey replacement. Here are the common ways to tell about a clogged heater core-

1. Poor Car Heater Performance


A faulty heater core will lead to poor heat performance in the cabin. Anything which prevents coolant flow through the center can prevent the heater to toast the cabin (e.g. exterior leakage or interior obstruction). In some circumstances, a heating core is just tired and starts leaking over time.

However, some cases can also lead to an early demise of the heater core. The heater’s core tubes are heated by the engine, and the blower engine pushes air into the inside of the car through the core pins. It can also be used to warm you up and defog the windscreen or to freeze it.

2. Low Coolant Level

If the core heater leaks are serious enough, the coolant pressure becomes lower than the required amount. As said, normally the heating core is behind the dashboard of your car. If you see the accumulation of the coolant on the floor of your car, it almost makes sure the core of the heater leaks.

External leaks from the radiator pitch, or from the radiator’s connections. A defective seal on the cap, where the pressurized coolant might seep off, is used to seal the radiator cap. Internal leaks in places such as the engine head gasket where coolant might flow.

3. Mist On The Windshield

The coolant of your automobile goes through the heater core, whenever you modify the climate control. Your car fan will then force the air through the heater to blow through the air. And look, warm air flowing through the interior of your car. Let us talk back to the topic when your heater core leaks, the coolant pool blows through the core.

Together with the heat of the fan when the heater core leaks. Coolant in this stage is somewhat grassy and nasty. That your front windscreen is sprayed into the windshield leaves behind a foggy movie. Coolant may be less chemical and nicer but you should not really try to taste it.

4. Engine Overheating

One of the biggest symptoms that you’ll find while learning how to tell if your heater core is bad or clogged. A low coolant level (from a leaking heater core) can produce surges and damage to the engine. Even a blocked heating core can block coolant flow sufficiently for overheating.

The clogged core can also stop coolant circulation and potentially damage the engine. Even a stuck heater can inhibit the adequate circulation of coolant, which causes your motor to run hot.

How To Test For A Clogged Heater Core?

Since the core of the heater is normally placed below the dashboard, it can be difficult to test it. However, a few ways can be used to check for heater and blockage core leakage. You should make sure that the remainder of the cooling system works properly before testing the heater core.

Use an infrared thermometer to test the heater core once you have ruled out other problems with the cooling system. You can only do an inferior release of the test with your hands when you do not have access to such a tool.

How Dangerous Is Coolant Leak Inside Cabin?

You should also know about this while learning how to tell if your heater core is bad or clogged. Serious consequences might occur when your engine is too warm or too cold, therefore maintaining this system is very important.

The Agency for Toxic Substances and Disease Registry states that it is not deemed dangerous in tiny quantities (ATSDR). On the other hand, the ingestion of ethylene glycol and methanol is dangerous and toxic. It only takes a little anti-freeze to intoxicate the human body and cause life threats.

Cost Of Replacing Heater Core

The substitution of the core can be costly and normally costs between $564 – $927 for the components and work. The pieces are not expensive, they usually cost $80-$234, however, the location of the heater core implies that the cost of labor is sometimes fairly high. You can also bypass the system cheaply.


In harsh winter weather such as that of New York, knowing about how to tell if your heater core is bad or clogged can be really handy. If you still have any questions, then let us know about them in the comments.

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