Chasing a ghost (knock)

[Oldsteel68]

03 Z71 5.3 90K Ive had a knock which sounds like lower end to me for the past few months. Havent had time to worry about it. But now Im caught up with things and tonight it drove me nuts to the point where I was in my street for 4 hours listening with a long screwdriver.

When I first start the truck after its sitting for a while, i get some lifter noise which seems to quiet down after about 30 seconds. I then got out of the truck and listened through the wheel well.. I still hear it.. Open the hood and take a listen from up top, dont hear it.. Back to the wheel well, hear it.. Grabbed a flashlight and a screwdriver, went under the truck.. I hear it. Screwdriver on oil pan -not louder. Side of block -not louder Bellhousing -not louder Felt around for exhaust leaks, burned the $%^# out of my arms, didnt feel any leaks.. Also checked valve covers, water pump, alternator...

WHAT IS THIS KNOCK??

I just drained a qt and dumped in a lucas, took it for a spin, topped off with 93 octane gas (i know its not nessasary, but was just praying...) May just be all in my head, but I almost want to say it got worse with the lucas.... Any ideas??

Last oil change i put 10w40 mobil 1 and delco filter hoping it would quiet it down. Last night i added the lucas.

I only hear it at idle near the wheelwell, or when parked next to a car, wall or fense..

Thanks

 

[blueflamed03]

start up clatter is normal. There are some looser tolerances on these, but are you using any oil? Having to add any? No SES light? No mechanical issues other than hearing a faint knock?

 

[TheYuk]

Which wheel well do you here it from? Mine makes the same kind of noise and I narrowed it down to the a/c compressor.

 

[M3PO]

start up clatter is normal. There are some looser tolerances on these, but are you using any oil? Having to add any? No SES light? No mechanical issues other than hearing a faint knock?

Agreed, my '02 Z71 did this on cold start up for the 3 years I owned it. I think if you do a search on it, you are one of many, and many believe there is no problem.

 

[Kman]

Are you hearing piston slap?

Make a noise like this?
http://www.youtube.com/watch?v=4Aaz5wNM3vI