My moms 05 5.3 started making a ticking/knocking sound when you first start it up, then it seems like it goes away, or used to. It seems like it is getting a little worse now and you can hear it while driving around town, but not on the highway, i think because of the noise. Truck is bone stock with 150K miles. It seems like its coming from the drivers side at the top of the engine, but you can hear it best from the top of the wheel on the drivers side.
heres a vid:
http://www.youtube.com/watch?v=Rs5z0BqfAxY

 

Start with pulling the valve covers... What were you doing when it started making the sound??

 

Just started it up one morning and it started doing this. Yeah we"ll pull the covers off and check it out.
I was thinking maybe a lifter?

 

sure sounds like a lifter

 

hmmmm my truck has made a similar but much quieter sound for a while now. same tempo. buddy of mine asked about it last night fearing it might be his truck. 6 liter is cheaper than cam, lifters, and all the gaskets. hmmmm, anyone got a good deal they know of???

 

I think im going to get a 6.0 for my truck then just put my 5.3 into this truck. Then everyone wins

Ill be on the hunt for an lq9 very soon also

 

Watch the oil pressure when you start it up. see if the pressure is lower when it ticks than it is when it doesn't. May need to add some lucas if so.

 

lifter, valve spring or rocker is my guess... by pulling the valve cover you can eliminate the spring and rockers

 

I've seen a cam lobe grind down and a lifter getting trashed and making that noise. But i would pull the valve cover and make sure everything is tight.

 

I had that same ticking noise, ended up being a worn cam lobe and lifter wheel.