Strange groaning noise behind dash

[DTS419]

Hi,

2001 Silverado. The last couple mornings it has been cold here in PA. I have been hearing a strange low rattling that sounds almost like a groan coming from somewhere behind the instrument panel. It is very sensitive to the throttle and the noise intensifies by even slightly increasing the throttle. After about 10 minutes when the truck is warmed up, the noise goes away. I have reached and looked around under the dash but haven't noticed anything that is loose or rattling. I also just had the knock sensors replaced and drivers side exhaust manifold gasket replaced at dealership. Could this be related?

[Jsdirt]

You could be hearing a small exhaust leak between the manifold and exhaust pipe, since you mentioned the manifold gasket was just replaced. It sounds small enough that when it heats up enough, it seals up.

 

I'd bring it back to them & have them check it out. Won't cost you anything but your time.