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Loud humming noise when idling in cold temps

Taylor_S

By Taylor_S
in 6.6L Duramax Diesel (L5P)

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Taylor_S New Member

Taylor_S

Posted
Posted (edited)

We recently purchased a 2022 GMC Sierra 3500HD diesel, and just noticed a loud, repetitive noise while idling. It starts, stops, and starts again in a rhythmic timing. It sounds like it’s coming from the air intake area, but I’m no mechanic so I’m not sure what it is. It doesn’t do it consistently, and I notice it more on colder days (30F or below) when letting it warm up in the morning. I’ve found similar discussion which mentioned it being the fan clutch, but others say they’ve replaced it and the sound continues. Is this just an annoyance or something that will wreck the vehicle if it’s not addressed? We haven’t even made the first payment on it yet so I’m pretty distraught over a potential costly repair. It only has 9k miles on it and is practically brand new. This truck was purchased to haul my living quarters horse trailer all over the country, so this has me concerned as I don’t want to have any major issues while on the road with a loaded trailer. 

Edited by Taylor_S
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ArrowsmithPML Enthusiast

ArrowsmithPML

Posted
Posted

Diesels make all sorts of noise in the cold. But around -2 C / 30  F there shouldn't be any significant noise with the exception of the wrong fluids, lose filters (check the air filter seat and housing) and the fuel pump and filter (on the frame rail below the fuel filler location).

 

These trucks need to be plugged in at -10 C to ensure the DEF tank doesn't freeze. I plug my '21 in for nearly 4 months straight but...

GMCustomerService Senior Enthusiast

GMCustomerService

Posted
Posted
On 3/21/2025 at 6:34 AM, Taylor_S said:

We recently purchased a 2022 GMC Sierra 3500HD diesel, and just noticed a loud, repetitive noise while idling. It starts, stops, and starts again in a rhythmic timing. It sounds like it’s coming from the air intake area, but I’m no mechanic so I’m not sure what it is. It doesn’t do it consistently, and I notice it more on colder days (30F or below) when letting it warm up in the morning. I’ve found similar discussion which mentioned it being the fan clutch, but others say they’ve replaced it and the sound continues. Is this just an annoyance or something that will wreck the vehicle if it’s not addressed? We haven’t even made the first payment on it yet so I’m pretty distraught over a potential costly repair. It only has 9k miles on it and is practically brand new. This truck was purchased to haul my living quarters horse trailer all over the country, so this has me concerned as I don’t want to have any major issues while on the road with a loaded trailer. 

We would like to learn more about this mysterious sound coming from your Sierra, Taylor. So that we can assist, we ask that you send us an email at [email protected] with your full VIN, mileage, and the name and address of your dealership. Once we have this, we can reach out to the team at your dealership directly! By sending us a message, you consent to the information you provide being monitored and recorded by GM or those acting on GM’s behalf, subject to the GM Privacy Statement: https://www.gm.com/privacy-statement.

  • 3 weeks later...
Crazy Canuck Enthusiast

Crazy Canuck

Posted
Posted
On 3/21/2025 at 9:20 AM, ArrowsmithPML said:

Diesels make all sorts of noise in the cold. But around -2 C / 30  F there shouldn't be any significant noise with the exception of the wrong fluids, lose filters (check the air filter seat and housing) and the fuel pump and filter (on the frame rail below the fuel filler location).

 

These trucks need to be plugged in at -10 C to ensure the DEF tank doesn't freeze. I plug my '21 in for nearly 4 months straight but...

I could be mistaken but I don't believe the DEF is heated when plugged in.  DEF freezes at -11C and it just freezes until the heater thaws it (powered by the truck when running).  It does not expand like water.  Agree though when cold, the Diesels make all sorts of noise as the idle up, drag the torque converter or whatever.

newdude Senior Enthusiast

newdude

Posted
Posted
On 3/21/2025 at 9:20 AM, ArrowsmithPML said:

Diesels make all sorts of noise in the cold. But around -2 C / 30  F there shouldn't be any significant noise with the exception of the wrong fluids, lose filters (check the air filter seat and housing) and the fuel pump and filter (on the frame rail below the fuel filler location).

 

These trucks need to be plugged in at -10 C to ensure the DEF tank doesn't freeze. I plug my '21 in for nearly 4 months straight but...

 

 

DEF heater has nothing to do with the block heater.  The DEF heaters are their own thing that are powered by the truck when running.  Heater in the tank and then one or two in the fluid supply line.

Sonny R Enthusiast

Sonny R

Posted
Posted

I am having the same sound. No good answer on what it could be. Sounds like a cow mooing. Goes away once the engine warms up. Very aggravating noise.

Maher Usman New Member

Maher Usman

Posted
Posted
On 3/21/2025 at 4:34 PM, Taylor_S said:

We recently purchased a 2022 GMC Sierra 3500HD diesel, and just noticed a loud, repetitive noise while idling. It starts, stops, and starts again in a rhythmic timing. It sounds like it’s coming from the air intake manifold area, but I’m no mechanic so I’m not sure what it is. It doesn’t do it consistently, and I notice it more on colder days (30F or below) when letting it warm up in the morning. I’ve found similar discussion which mentioned it being the fan clutch, but others say they’ve replaced it and the sound continues. Is this just an annoyance or something that will wreck the vehicle if it’s not addressed? We haven’t even made the first payment on it yet so I’m pretty distraught over a potential costly repair. It only has 9k miles on it and is practically brand new. This truck was purchased to haul my living quarters horse trailer all over the country, so this has me concerned as I don’t want to have any major issues while on the road with a loaded trailer. 

Could be the fan clutch, but since it's mostly on cold mornings, it might just be normal. If others have replaced it and the noise still happens, it could be something like the turbo or air intake. With only 9k miles, you’re probably still under warranty, so get it checked out. It’s likely not a big issue, but better to be safe, especially with towing.

GMCustomerService Senior Enthusiast

GMCustomerService

Posted
Posted
On 4/9/2025 at 5:23 PM, Sonny R said:

I am having the same sound. No good answer on what it could be. Sounds like a cow mooing. Goes away once the engine warms up. Very aggravating noise.

Have you connected with your dealership regarding this noise concern, Sonny? They are our eyes and ears in the field, and are best equipped to take a look and address your concerns. We are happy to act as an extra layer of assistance, and we ask that you reach out via email to [email protected] we can help. We look forward to your email. By sending us a message, you consent to the information you provide being monitored and recorded by GM or those acting on GM’s behalf, subject to the GM Privacy Statement: https://www.gm.com/privacy-statement. 

  • 2 months later...
Sonny R Enthusiast

Sonny R

Posted
Posted

Yes, brought it to a GM dealer one morning. Cold temps, engine was not warmed up and it was "mooing". Tech said he never heard that before. That was this past winter. Hot now and the cow has left for the summer.

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