Strange noise from bottom rear of engine

[dammad]

My 08 Yukon Denali is making a very strange noise very shortly after start. It was running fine after a recent oil pump change/upgrade (high capacity) to resolve low oil pressure concerns. But now it is making the noise from this video.

Given the noise is loud and unexpected, I've not left the vehicle running much so can't tell if it disappears when warmed up. I did quickly check that the noise is not from the water pump or anything driven off the serpentine belts.

Any ideas? Help! Praying it is not catastrophic!

 

[Fless]

Sounds a bit like the starter isn't quite disengaging.

 

[rdezs]

That is concerning. And you're sure it's not coming from outside the engine? It does seem to match crankshaft RPM at idle. Did you follow the procedure to center the oil pump? Melling says to tighten two opposing bolts barely finger tight, rotate the engine twice, and then torque them down. It's about the only thing I could think of related to the work you did.

 

[rdezs]

Regarding the starter .... Did you use new starter bolts and install to the proper torque?

 

[rdezs]

It's the correct pitch of sound like something's touching the flex plate for sure

 

[j91z28d1]

Sounds a bit like the starter isn't quite disengaging.

yeah, starter drive touching the fly wheel is what it sounds like to me too

 

[strutaeng]

I had a similar issue on my 06 LQ4 a few months ago, but much louder. I did some checking, but finally crawled under there and it was pretty obvious. The little gear on the starter didn't retract and made a horrendous metallic sound. New (remanufactured) starter and I sent it.

I took a video but have never uploaded it to YT...

 

[Geotrash]

My 08 Yukon Denali is making a very strange noise very shortly after start. It was running fine after a recent oil pump change/upgrade (high capacity) to resolve low oil pressure concerns. But now it is making the noise from this video.

Given the noise is loud and unexpected, I've not left the vehicle running much so can't tell if it disappears when warmed up. I did quickly check that the noise is not from the water pump or anything driven off the serpentine belts.

Any ideas? Help! Praying it is not catastrophic!

+1 to "It's the starter!" Common issue.

 

[Doubeleive]

My 08 Yukon Denali is making a very strange noise very shortly after start. It was running fine after a recent oil pump change/upgrade (high capacity) to resolve low oil pressure concerns. But now it is making the noise from this video.

Given the noise is loud and unexpected, I've not left the vehicle running much so can't tell if it disappears when warmed up. I did quickly check that the noise is not from the water pump or anything driven off the serpentine belts.

Any ideas? Help! Praying it is not catastrophic!

likely the starter or the catalytic converter material came apart inside the cat.
a stethoscope will determine which one it is.