How To Tell If Your Furnace Heat Exchanger Is Cracked

Heather Robbins
by Heather Robbins

Don’t ignore your instincts if you suspect your gas furnace has a cracked heat exchanger. Not repairing a damaged heat exchanger in a timely manner can cause serious health issues for your family. Among the toxic gases released into the air is carbon monoxide. It’s important to check to see if it’s cracked and then stop all use. But, how do you tell if it’s broken?

To tell if your heat exchanger is cracked, you will need to look for the signs. If water collects at the base of your furnace, or there’s excesses soot or strong smells coming from your furnace, it’s most likely cracked. Also, if the fire is yellow or there’s any corrosion, you most likely have a cracked exchanger.

In the U.S., hundreds of deaths are caused by cracked heat exchangers and carbon monoxide poisoning. You should regularly inspect and maintain your HVAC system if you want your family to be safe. In this guide, we’ll discuss the heating system’s heat exchanger components.

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How Does A Heat Exchanger Work?

When it is cold outside, a heat exchanger in a gas furnace warms the air inside to keep the house warm. Coils and tubes of the system are used to loop constantly and heat the air passing through it.

As the furnace connects to the chimney vent, the heat exchanger system begins at the burner assembly. A metal chamber surrounds the heat exchanger so that your entire home can be held at a comfortable temperature. The furnace’s combustion gases are channeled into the heat exchanger chamber to heat the metal walls.

While your system is running, the return ducts in your home are sucking in cold air and passing it along with the heat exchanging unit. Through ducts, you will receive warm air from the heat exchanger wall once it is heated up. On the other hand, the heat exchanger will emit combustion gases into a vent that channels them outside the house.

Signs Your Heat Exchanger Is Cracked

When you look at the heat exchanger on your furnace, it’s difficult to tell whether it’s damaged or not. So be aware of the cracks in the heat exchanger. How do we tell if our heat exchangers are bad? For more information, keep reading.

Water Collects

You may find water on the floor at the furnace’s base even if there is no condensation issue. This may indicate a problem with the heat exchanger. If you want to discover the root cause of the case, you should contact a local HVAC contractor.

Leaks around the furnace can also result from cracked heat exchangers and other factors. If your furnace is connected to a humidifier, it could leak. If the internal drainage system of the HVAC system is clogged, this could also be a cause.

Strong Smells From The Furnace

The heat exchanger of your heating system may be cracked if it produces a strong and unpleasant smell. A significant characteristic of the fumes is that they typically smell like formaldehyde; they are incredibly toxic when inhaled.

A formaldehyde-like odor is indicative of a broken furnace so contact a professional HVAC contractor today. You may put yourself in further danger or risk further harm if you ignore the problem.

There’s Excess Soot

There will be a lot of soot created in your furnace when there is a lot of carbon in the heating system. This is commonly referred to as incomplete combustion, which is when the furnace fails to burn the gas entirely.

It may be due to several reasons, such as faulty burners, for the fuel to not burn completely. An exchanger with a cracked surface may also contribute to increased soot production in the heating system.

Fire Looks Yellow

It is normal for furnace flames to be blue in color. The constant blue flame on your furnace indicates that the furnace’s heat exchanger functions correctly, so there’s no need to be concerned.

It can, however, indicate that the burner is dirty or that the heat exchanger has cracked if your furnace produces a yellow flame. If, however, the flame is yellow and also flickers, the chances are high that the furnace has further damage.


There is a high probability that your furnace’s internal components also wear out when the external components start showing wear. You may also have cracked heat exchangers.

As the furnace cools and heats, stress cracks develop on the components, which occur when the components contract and expand intermittently. Furthermore, exposure to fumes with chlorine or moisture can corrode the furnace components.

Reasons Your Heat Exchanger Cracked

Cracks in heat exchangers are caused by a variety of causes:

  • Excessive Heat: It is common for furnaces’ heat exchangers to crack when they are overheated. In a heating system with slow airflow, heat can build up and eventually cause it to malfunction. Maintaining the furnace regularly will improve airflow, which is why you should do so.
  • Furnace Age: Heat exchangers of furnaces usually last 15 years. You are likely to find cracks in the heat exchanger if your gas furnace is about that age. It is best to prepare a replacement in case it breaks so that you don’t experience any inconveniences.
  • Dust Accumulation: Filters, blowers, and coils can become clogged when dirt and dust accumulate in the heating system. Because of this, the system will not be able to gain enough airflow. A furnace that is overheated will perform less efficiently.
  • Rusting Of Metals: Moreover, corrosion or rusting are significant causes of heat exchanger cracks. Metals corrode and can cause cracks in heat exchangers if they are exposed to rust. The components of your system can develop cracks if you haven’t maintained them properly.\
  • Alternate Heating And Cooling: Constant heating and cooling can also cause a heat exchanger to crack. The metallic wall of the chamber will also expand and contract continuously as the exchanger heats and cools intermittently. This will lead to the metal component wearing down and cracking.

Risks Of Cracked Heat Exchangers

Heat exchangers that are cracked can pose a great deal of risk. In addition to endangering your health, you will also cause further damage to the system. These are some of the risks associated with a cracked heat exchanger in a nutshell:

  • Poisonous gases: A cracked heat exchanger can release toxic gases if fuel oil, propane, or natural gas are used to heat a home. Many health problems can be caused by fossil fuel gases like carbon monoxide and carbon dioxide. When it leaks out, carbon monoxide gas produces headaches, nausea, vomiting, and dizziness. Carbon monoxide, in large amounts, can cause heart complications if prolonged.
  • Efficiency. The efficiency of the furnace will also be affected by a cracked heat exchanger. The furnace becomes burdened by heating your entire house with the warm air escaping from the chamber. You will be unable to maintain a comfortable indoor temperature as a result.

What To Do If Your Heat Exchanger Is Cracked

You shouldn’t try to fix your furnace yourself if you believe that the heat exchanger has been damaged. The next step is to contact a professional HVAC contractor to inspect the furnace once the symptoms of the furnace heat exchanger crack have been verified.

  • Do not use the furnace. You’re putting yourself at greater risk if you continue to use the furnace despite showing signs of a cracked heat exchanger. As long as toxic gases leak into your home, you will suffer from health problems. Shutting down the furnaces is the most effective way to prevent this.
  • Replace the part. If your heat exchanger is cracked, you will need to replace it since you cannot repair it. It is crucial to take into account, however, that the system is quite old. As an example, if the furnace lasts for about 15-20 years, you can replace the whole thing.
  • Call a professional. Consult an experienced HVAC technician before attempting to replace a cracked heat exchanger or purchase a new furnace. Experts will offer advice on how to maintain your furnace. The maintenance schedule will even be provided to you.

How Much Does A Heat Exchanger Cost?

In order to replace a heat exchanger, you’ll need around $650 to $1200 to buy and install the new exchanger. Therefore, installing an old heat exchanger on a new furnace will not be cost-effective. A brand new heat exchanger can cause the furnace to fail otherwise.

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Final Thoughts

If a heat exchanger in your furnace is cracked, the chances of it failing are high. In addition, it is a health hazard that may cause your family to be poisoned by carbon monoxide. By maintaining the furnace regularly, you can prevent this from happening. However, if it cracks, you must replace it immediately.

This is a job that’s the best fit for a professional, as it’s vital that the part is replaced correctly. Therefore, it’s a good idea to call at least three different HVAC specialists to compare prices. That way, you get the best deal for your money. Check to ensure they have good reviews, too, so you can trust you’re in good hands.

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Heather Robbins
Heather Robbins

Heather is a passionate writer who loves anything DIY. Growing up, she learned everything from home repairs to design, and wants to share her tips with you. When she's not writing, she's usually hiking or searching for her next DIY project.

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