8 Heating System Noises & What They Mean

February 19, 2021
new furnace install carrier smarthouse

The best kind of heating system is one that quietly keeps your St. Louis home comfortable all through the winter months. But unfortunately, that doesn’t always happen, and when your furnace, boiler or heat pump starts running into issues, you’ll often be able to hear something isn’t right.

Expert HVAC technicians, like the team at SmartHouse Heating and Cooling, have lots of experience diagnosing malfunctioning heating systems, but the average homeowner doesn’t. So, if you’re hearing a new noise coming from your heating system and aren’t sure what it means, check out this useful guide to common heating system noises and what can cause them.



If you hear a banging sound when your furnace turns on, it’s likely the sound of a delayed ignition caused by dirty burners that need to be cleaned. On the other hand, if your furnace makes a banging noise when it shuts off, it’s likely to be the result of your ductwork contracting as the metal cools back down.


A gas furnace making a loud hissing or whistling sound is often the sign of a dirty air filter or an air leak.  If changing your air filter doesn’t stop the noise, schedule a furnace repair call from a SmartHouse technician, who will find and close up any leaks.


A clicking furnace sound could be caused by:

  • Pilot light not functioning correctly
  • Electrical issues
  • Worn motor bearings


A rattling sound from your furnace could be as simple as a loose screw or panel, but it could also be the sound of a cracked heat exchanger, which is a serious problem and could lead to carbon monoxide leaks in your home.



If limescale builds up on your heat exchanger, it will get too hot, creating steam bubbles that “pop” and make a banging (or sometimes a whistling) sound. This is called kettling, and you’ll want to call a professional specializing in boiler repair to fix the issue.


A gurgling boiler sound—you’ll hear this running through the pipes in your home—is usually the result of air bubbles trapped in the pipes. This issue can also affect the boiler’s ability to heat your home, so you’ll want to have it addressed sooner rather than later.

Heat Pumps


A clanging “metal on metal” sound coming from your heat pump is usually an indication that something’s happening with your fan blade. It could be that a blade has bent, or it could be that a piece of debris is stuck in the unit.

Loud humming

Loud humming noises from your heat pump are not a good sign. Whether an electrical component in your unit has worn out or you’re hearing the sound of a seized fan motor, you’ll want an HVAC technician to take a look at your system and identify the problem.

Take the Guesswork Out of Heating System Troubleshooting with SmartHouse

The problem with trying to diagnose the issue with your furnace yourself is there are many different reasons why your furnace, boiler, or heat pump could be making a strange sound, and while some issues are more common than others, it’s not smart to make guesses or roll the dice when it comes to heating your home. The best thing you can do to get your heating system working quietly again, and avoid expensive and inconvenient breakdowns, is to call in a heating and cooling system professional.

SmartHouse Heating and Cooling’s NATE-certified HVAC technicians have the training and experience to get to the bottom of any heating problems you might be having in your home. From heating repair to furnace tune-ups, our team can help make your Brentwood or Clayton home comfortable again quickly.

Is your St. Louis heating system making a strange new sound? Call or contact us today and schedule an appointment with the local HVAC experts at SmartHouse.