Skip to Content

Furnace Making Loud Rumbling Noise? 5 Common Causes + Fixes

Even though a furnace can last well over a decade, these devices are not without their problems. Even newer furnaces can start to create rumbling noises that can keep you up at night. A furnace making a loud rumbling noise is something you do not want to ignore.

A furnace is makinga loud rumbling noise if the burners or pilot light are dirty, there’s debris on the draft inducer motor, the panels are loose, or there’s a crack in the heat exchanger. Fixes include cleaning the furnace, screwing the panels back into place, and replacing the heat exchanger.

This article will help you understand why your furnace is making a rumbling noise. I’ll go over the most common causes, including one that can lead to dangerous effects if not taken care of. I’ll also tell you how to fix each issue so that you can sleep peacefully at night. 

The Burners Are Dirty

We begin by considering some of the more common problems behind a rumbling noise in the furnace. This is also one of the simpler factors to fix, making it a good starting point. 

When gas is sent to the ignitor, the ignition process will create flames on the burners. The burners then maintain the flames to keep your house nice and toasty. 

Over time, debris from dirt and gases start to collect on the burners. This can cause the small holes in the burners to get blocked. 

When the airflow becomes blocked, there isn’t enough gas passing through for a flame to be created. 

The result is an interference with the combustion process, which creates a loud rumbling noise. 

How To Fix

If you already clean your burners and other parts of the furnace regularly, this might not be the problem. However, if you haven’t cleaned the furnace’s interior recently, this is a good place to start: 

  1. Turn the furnace off and locate where the burners are located. 
  2. Open up the panels on the furnace to get access to the burners. 
  3. Remove the burners.
  4. Use a vacuum cleaner with a brush attachment to clean the burners. The brush should be soft to avoid damaging the burner. 
  5. Once vacuumed, move on to compressed air. This helps to remove debris in the harder to reach areas of the burner. 
  6. Turn the burner around and give it a shake to get rid of even more debris. 

This video walks you through the steps to clean furnace burners:

The Pilot Light Is Dirty

Some furnaces still use a pilot light to assist with the combustion and ignition process. This generally accounts for older furnaces, as newer models use alternative methods for the combustion process. 

If your furnace has a pilot light, it’s a possible cause behind the furnace’s making a loud rumbling noise. If the pilot light isn’t adjusted correctly or there’s a collection of debris on top of it, it can cause all sorts of noises.

How To Fix

A visual inspection of the pilot light will usually be enough to determine if it’s the cause behind the unpleasant rumbling sound. See if the flame is lower than it should be. Also, take note of any visible debris on the light. 

It’s relatively common for soot to accumulate on the pilot light, a black, flaky substance.

Here’s how to clean a pilot light:

  1. Remove the pilot light from the furnace to clean it. You may need to use a wrench. 
  2. Use a wire brush to clean the pilot light. Don’t push too hard with the wire brush. You simply want to remove the debris that has collected on the pilot light. 
  3. Some people find that a metal file is useful too — particularly for the pilot light’s smaller areas. 

Below is a video that shows you how to clean a pilot light: 

There’s Debris on the Draft Inducer Motor

If the rumbling sound only occurs when you start the furnace up, you should take a closer look at the draft inducer motor. 

The draft inducer motor is an important part of the furnace. It’s connected to the heat exchanger and the flue pipe. Gases produced during the combustion process are pushed toward the draft inducer motor. These gases are then sent through the flue pipe, ensuring the toxins don’t enter your home. 

When the draft inducer motor is dirty, it may not effectively push the combustion gases toward the right direction. This will not only cause a rumbling sound but can also lead to toxic gases entering your home. 

How To Fix

Before you begin, start by removing the draft inducer motor from the furnace. Look for a build-up of debris on the motor. Use an appropriate tool to remove this. 

You can use compressed air to blow out smaller particles. 

Take note that the draft inducer motor may be faulty. If there’s no visible debris that may block the flow of gases, consider the possibility that the motor itself is the issue. In this case, consider getting a replacement. 

Here’s a video that explains the replacement process:

The Panels on Your Furnace Are Loose

There are multiple panels found on a furnace. When these panels become loose, they can create a rumbling sound while the device is turned on. The sound will likely be more bothersome if the panels are completely loose. In most cases, however, the panels have a screw that is loose — but not out. 

How To Fix

The solution here is rather simple. You have to check all access panels on the furnace to see if there are loose connections. Use a screwdriver to fasten the screws on all panels. 

There’s a Crack in the Heat Exchanger

When the heat exchanger is cracked, carbon monoxide can enter your home. This is a dangerous problem that can lead to a safety hazard. Consider the possibility of a crack in the heat exchanger when there’s a rumbling sound coming from the furnace.

How To Fix

If there’s a crack in the heat exchanger, it’s best to replace the component. Safety should be a priority for looking at a furnace. Trying to repair the crack can lead to more problems in the future. 

If you decide to replace the heat exchanger, it’s generally best to seek a professional’s services. The heat exchanger needs to be unplugged from the rest of the system, then loosened and removed. Once this is complete, a new heat exchanger is placed into the furnace and then rewired accordingly. 

Summary

A heat exchanger with a crack can be why a furnace makes loud rumbling noise and tends to be a harmful issue. Other reasons for the furnace making this noise can be related to loose panels on the device or certain parts packed with debris and soot. 

Some of these causes can be rather dangerous, which is why you should consider getting the help of a professional.

Author

  • Steve Rajeckas

    Steve Rajeckas is an HVAC hobbyist with an avid interest in learning innovative ways to keep rooms, buildings, and everything else at the optimal temperature. When he's not working on new posts for Temperature Master, he can be found reading books or exploring the outdoors.

As an Amazon Associate, we earn from qualifying purchases. We may also earn commissions if you purchase products from other retailers after clicking on a link from our site.