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How to Tell If My Heat Exchanger Is Cracked

Heat exchangers play a pivotal role in your gas furnace, allowing heat generated by combustion to create warm air for your home. A cracked heat exchanger can pose serious risks, including a carbon monoxide leak and carbon monoxide poisoning. In this guide, we'll explore how to identify if your furnace's heat exchanger is cracked and why prompt action is crucial.


Understanding the Furnace Heat Exchanger

Before diving into the signs of a cracked heat exchanger, let's briefly understand its function. The heat exchanger is a vital part of your furnace or heating system. Its primary role is to transfer heat from the combustion process to the air that circulates through your home. It consists of a series of tubes or coils where hot combustion gasses flow. If the heat exchanger cracks, it can lead to dangerous consequences.


Cracked Heat Exchanger Symptoms

Visible Cracks or Holes

One of the most apparent signs of a damaged heat exchanger is a visible crack or hole. One primary cause is the natural wear and tear to the heat exchanger's walls that occurs over time due to the repeated cycles of heating and cooling during normal operation. This thermal stress can eventually weaken the metal, making it susceptible to stress cracks. A clogged air filter can even cause heat exchanger cracks due to overheating the system.


Corrosion is another factor, especially in older gas furnace systems or those exposed to moisture. The corrosive effects gradually eat away at the metal, compromising its integrity. Poor maintenance practices, such as neglecting regular inspections and cleanings, can contribute to the accumulation of debris and soot, further accelerating the deterioration of the heat exchanger. Additionally, manufacturing defects or poor installation can also play a role in the development of cracks in heat exchangers.


Strange Furnace Noises

Unusual sounds emanating from your furnace cabinet can be indicative of various issues, and a cracked heat exchanger is one of them. A cracked heat exchanger can produce unusual noises due to the disruption of the combustion process within the furnace. When the heat exchanger is compromised, the integrity of the combustion chamber is compromised as well.


As the cracked metal expands and contracts with the temperature changes during operation, it may create popping or banging sounds. The irregular flow of combustion gasses through the damaged exchanger can lead to hissing or rumbling noises. These atypical sounds serve as audible indicators of an underlying issue and should not be ignored.


Carbon Monoxide Detector Alarms

Carbon monoxide is a colorless, odorless gas that can be emitted if there's a crack in the heat exchanger. A cracked heat exchanger poses a serious risk of triggering a carbon monoxide detector due to the potential leakage of this odorless and colorless gas. The heat exchanger's role in a heating system involves facilitating the transfer of heat from combustion gasses to the air circulated in the home. When the heat exchanger is cracked, it can allow combustion byproducts, including carbon monoxide, to escape into the air that circulates through the system.


Carbon monoxide detectors are designed to sense elevated levels of this gas, and if a crack exists in the furnace heat exchanger, it becomes an avenue for the escape of carbon monoxide into your living spaces. The activation of the carbon monoxide detector serves as a crucial early warning system, alerting homeowners to the presence of this potentially lethal gas and prompting immediate evacuation and professional intervention to rectify the heat exchanger issue and prevent further health risks such as carbon monoxide poisoning.


Soot Buildup

A cracked heat exchanger can disrupt the combustion process, leading to the production of soot. This fine, black powdery substance is a byproduct of incomplete combustion and is typically expelled through the flue system. However, a bad heat exchanger allows the soot to escape into areas where it shouldn't be, accumulating in and around the furnace. Not only does this compromise the efficiency of the heating system, but it also serves as a visible red flag, signaling the need for immediate attention.


Inefficient Heating

A cracked heat exchanger can compromise the efficiency of your heating system and its ability to distribute warm air. If you notice a decline in your furnace's performance, such as uneven heating or the inability to reach the desired temperature, it's worth investigating the condition of the primary heat exchanger.


When the furnace's heat exchanger is cracked, it disrupts the efficient exchange of heat, causing a decline in the overall performance of the furnace. The crack in the heat exchanger can allow heat to escape or interfere with the combustion process, resulting in reduced heating capacity. Homeowners may notice uneven heating, persistent cold spots, or an inability of the system to reach the desired temperature.


A Change in Flame Color

A notable change in furnace flame color can serve as a visual cue indicating a damaged heat exchanger, particularly the presence of a crack. Under normal circumstances, the flame in a properly functioning furnace should burn blue. However, when a heat exchanger is compromised, it can alter the combustion process.


A cracked exchanger can introduce irregularities in the mixture of air and fuel, leading to incomplete combustion. Incomplete combustion often manifests as a change in flame color, with the flame appearing more yellow than blue. This color change is a result of the release of excess carbon monoxide, a byproduct of incomplete combustion.



A cracked heat exchanger can contribute to condensation around your furnace due to the disruption of the normal combustion process. The heat exchanger is responsible for transferring heat from combustion gasses to the air circulated throughout your home. When it develops a crack, it allows excess air to enter the combustion chamber, affecting the air-to-fuel ratio. This imbalance can lead to incomplete combustion, producing water vapor as a byproduct.


Why Prompt Action Is Essential

Cracked heat exchangers can be a very dangerous problem for homeowners, which is why it's so important to take action as soon as you notice any of the above signs from your furnace heat exchanger and call for furnace repairs.


  • Safety Concerns: The most critical reason to address a cracked heat exchanger promptly is safety. Carbon monoxide gas leaks can be life-threatening. The immediate evacuation of your home and contacting a professional for repairs is crucial if you suspect a cracked heat exchanger.

  • Preventing Further Damage: Ignoring the issue can lead to more extensive damage to your heating system. What might start as a small crack can worsen over time, potentially resulting in the need for a costly replacement of the entire furnace.

  • Energy Efficiency: A cracked heat exchanger can compromise the efficiency of your heating system, leading to increased energy consumption. Addressing the issue promptly not only ensures your safety but also helps maintain the energy efficiency of your home.

Steps to Take If You Suspect a Cracked Heat Exchanger

  1. Evacuate Immediately: If your carbon monoxide detector alarms or you notice any signs of a cracked heat exchanger, evacuate your home immediately. Do not ignore the warning signs.

  2. Contact Professionals: Call Boothe’s Heating, Air, Plumbing, Drains & Electrical or another reputable heating service immediately. Professionals have the expertise and equipment to assess the situation and perform the necessary repairs or replacements.

Additionally, there are a few important steps you can take to prevent issues with cracked heat exchangers and gain early warning of any problems.


  1. Schedule Regular Maintenance: Preventive measures are key to avoiding issues with your heat exchanger. Schedule regular maintenance with a qualified technician to ensure your heating system operates efficiently and safely.

  2. Install Carbon Monoxide Detectors: If you don't already have carbon monoxide detectors in your home, consider installing them. These devices can provide an early warning of potential issues with your heating system.

Understanding how to tell if heat exchanger is cracked is essential for the safety and efficiency of your heating system. Regular inspections, prompt action, and investing in preventive measures can go a long way in ensuring the well-being of your home and family. If you suspect any issues with your heat exchanger, don't hesitate to contact professionals for a thorough inspection and necessary repairs. Your peace of mind and safety are worth the proactive effort.


If you suspect your heat exchanger is cracked, schedule furnace repair service with Boothe's today. Our team will examine your heat exchanger to catch any issues and perform the necessary repairs to protect your family and ensure proper heating.