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Furnace Making Groaning Noise? 3 Common Causes (+ Fixes)

Your furnace makes all sorts of noises, many of which are completely normal. You’ll hear most noises when the furnace starts up and perhaps during the heating cycle. However, you need to realize when something serious is at play, and a groaning noise is something you shouldn’t ignore. 

Your furnace is making a groaning noise because the metal sheets on your furnace stretch from hot air, the bearings are worn out, or certain parts are under stress. You don’t have to worry about sounds caused by metal panels, but you should identify and replace the part making the groaning noise.

This article will give you an overview of common reasons for a furnace to make a groaning noise. I’ll also go over the methods you can implement to fix these problems to eliminate the groaning noise. 

The Metal Sheets Stretch From the Hot Air

We have to consider everything that can cause a groaning noise.

Let’s start with one of the more common reasons you may hear a groaning sound from the furnace — the stretching of metal parts. This may sound strange, but consider a situation where the weather is freezing. Maybe you only run the furnace at specific times. When the furnace is off, the cold temperature affects the metal panels that house the furnace. 

Once you turn the furnace on, the air heats up in and around the furnace. As heat builds up, the metal sheets stretch. This can create unpleasant sounds that you might describe as groaning.

How To Fix

There isn’t really a fix for this particular scenario. However, you must still ensure that this is the reason for the groaning – you don’t want to accidentally miss a problem that can lead to damage in the future:

  • Consider when you hear the sound. Take some notes, as this will give you a reference to determine if the noise happens only during heating cycles or startup.
  • Consider whether the sound is present after you start up the furnace following a period of inactivity. If this is the case, consider the weather conditions over the past few days. 

If temperatures were extremely low in the past few days, and you hear the groaning sound as the furnace is heating up, you solved the mystery. Expanding metal sheets are creating the sound. 

Unfortunately, you can’t do much about the groaning sound in this case. The noise shouldn’t last long, though, as the materials will stop making a sound once the heat has been distributed. If the sound remains, make further investigations to determine if something else is at play. 

Bearings Are Starting To Wear Out

There are multiple motors in a furnace system. These motors are connected to different types of fans. The blower motor is a good example. The blower motor rotates the blower fan. As the fan blows, it distributes air from the burners toward the ductwork. 

Bearings are mechanical parts used to assist with the rotation of fan blades. These parts are small but can cause significant problems when they break or wear out. These parts are situated between the motor and the fan. Note that all fans in your furnace have bearings — so you should check all of them. 

As bearings wear out, the cushioning that touches the motor’s moving metal parts gradually fades away. This exposes the bare metal parts. The metal-on-metal grinding sound produces the loud, constant groaning noise that won’t go away.

The sound may be more alarming, louder, and sharper if multiple bearings are worn out.

How To Fix

When bearings wear out, don’t attempt to repair them. Even though your furnace is made of heavy-duty materials, they still wear out eventually after years of use. The best way to fix this issue is to replace the broken fan bearings.

However, you first want to confirm that it’s the bearings causing the problems, not something else. Here’s how:

  1. Turn off your furnace.
  2. Open the main compartment.
  3. Check the bearings in all motors. This includes the blower, the inducer, and the motor attached to the flue line.
  4. Look for signs of corrosion. Even minor signs of damage or deterioration are sufficient to replace the bearing.

When a bearing wears out, replace it entirely. You should replace bearings regularly to ensure adequate functionality.

The video below shows you how to replace a bearing in the blower motor:

Stress on Furnace Components

Another possible reason for the groaning noise is excessive stress on furnace components. This is a tough one, as it can be challenging to determine. 

Different parts are under pressure as the furnace runs. When you leave the furnace on for extended periods, it builds up a lot of heat, and moving parts can face overheating issues. 

It’s often a minor problem with one part. For example, a misalignment between two parts can put more pressure on one part than the other, resulting in a groaning noise.

How To Fix

Since there are many parts in the furnace, it can be challenging to pin down the noisemaker.

You should consult with a professional for this fix. However, you can take a few initial steps before getting an HVAC expert on the job. 

Start by determining where the sound originates. Even though the sound may seem like it radiates through the entire furnace or HVAC system, you should still be able to determine where it’s coming from exactly if you listen closely. 

This can give you an idea of what part of the furnace is affected and creates an opportunity for assessing specific components. 


A groaning sound causing sleepless nights is the last thing you want in your home. The groaning sound may be related to worn-out bearings on the motor that need to be addressed before further damage occurs.


  • Jake Alexander

    Jake is a freelance writer from Pennsylvania who enjoys writing about science and sports. When he's not writing for Temperature Master, he can be found watching the NFL or playing basketball with his friends.

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