knocking noise

[Bentleymartin]

hey guys i have a 2005 Tahoe ls 4x4 with 123xxx. I have noticed a knocking noise on the top of the motor like under the vortec plastic shield thing. it sounds like a wood pecker. Also i have heard a knocking noise coming from the passenger rear like in the cargo space. Any ideas what these could be?

 

[tonymac617]

When does the knocking occur? Start up? During driving? and lastly does it go away after a while or is it constant?

 

[Bentleymartin]

constant but you cant hear it while driving only when your outside the vehicle

 

[tonymac617]

Could be piston Slap.

 

[Unstable]

What if the tapping goes away and only happens after it in idle?