2021 Duramax, what the heck is this sound?

Bighig · November 9

Hey guys!
First post, I'm sure I did it wrong, move me if needed!
Long time stalker here. Normally I some poor soul has had to deal with my issue and fixed it, but I can't quite find what exactly is going on through any forum I've seen.
Today I got up for work and remote started my truck. It ran for about 5 min before I went out to push snow off. It was about 30 degrees out. It was high idling the whole time. I then heard a very obvious groaning sound coming from the front of the engine bay, toward the fan and shroud as far as I can tell. Kinda sounds like a lawn mower or leaf blower on the videos I took and is less obvious than it is in person.Something vibrating or rubbing? I only hear it at idle outside the truck. It either doesn't happen or isn't loud enough while driving. Can sort of here it in the cab while idling.
Any ideas? Stopped by the local diesel shop and they've never heard it before.

https://youtu.be/fu2WAYbbfSc?feature=shared

bruceb58 · November 9

I don't think I have ever been able to hear the sounds someone is concerned about watching/listening to these videos. I can't hear it with yours either.

Does it go away when completely warmed up?

Edited November 9 by bruceb58

Bighig · November 10

On 11/9/2024 at 11:41 AM, bruceb58 said:

I don't think I have ever been able to hear the sounds someone is concerned about watching/listening to these videos. I can't hear it with yours either.

Does it go away when completely warmed up?

It's only there when it high idles, so yes, when it returns to regular idle RPM.

gemarsh · November 11

I know when mine goes into elevated idle, it sounds like the fan clutch engages, but it's more of a roar of air. Takes a few minutes to engage.

Wait till it's around 0°F and the ecm stalls the tranny to warm it up! It's kinda fun setting outside of the truck in the shop for 15 minutes listening and watching the truck do it thing.