knock/ marbles sound on startup

i bought a 3.1 liter '99 monte carlo that only has 27,000 miles on it and is in excellent condition the only reason it was getting rid of was the guy wanted something that can haul a large boat. anyhoo everytime you start the car up weather it be hot or cold there is a slight knocking sound or i guess more of a couple marbles getting knocked around in metal. Its not a loud sound and it only lasts a split second right after you let go of the key. and the sound appears to be coming from the left side of the engine compartment right under where you add brake fluid at. I dont know much about vehicles so thats why im here. did i buy a lemon? or is it a simple problem to fix? the car was bought at a dealer only a couple days ago. it has a bumper to bumper warrenty with it. can i nail them with the lemon law if the engine needs overhauled or do you think the warrenty will cover it? its a ford warrenty since it was bought at a ford dealer. thanks

There is probably a pushrod problem or there is something under a valve cover.
Take it back.

It's called piston slap,checkout www.gm pistonslap.com

That website was nothing but junk and popups.

if the extended warranty was transferrable to you, the new owner, get your car in ASAP. I agree it sounds like piston slap, and that's big $$$$.