2015 Yukon 5.3 4x4 Cold Start Noise.

[jay67chevy]

Mechanic has had the truck in the shop twice. Can’t find the culprit and suggests it coming from the top end at startup due to oil flow back.

I’m going crazy trying to find the noise elsewhere. No missing bolts on exhaust, can’t find any exhaust leaks, noise goes away after 30secs and a whippering remains during acceleration for the first min or so of driving. She runs smooth and strong after it warms up. 200k on the odometer.

I thought the sound is coming from the starter and sprocket maybe not retracting all the way back in, but that idea got shut down by this mechanic.

Here’s a video link.

 

[jay67chevy]

Here’s one more during the first min or so until it warms up.

 

[Fless]

WAG: starter not retracting fully?

 

[MobileHomie]

The video from outside sounds like an exhaust leak, the noise goes away once the manifold heats up and closed the gap. Older ford 460s are famous for this trait. The interior, dunno, unless it is exhaust whistling out the manifold flange.

 

[stockmaster]

Hi @jay67chevy have a 2017 suburban with 5.3 that has the exact same symptoms. Any updates on the diagnosis? Curious before I start to take apart the block.