Loud Knock when Cold HELP!!!!!
Thread Starter
Staging Lane
Joined: Feb 2005
Posts: 56
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Loud Knock when Cold HELP!!!!! Ok here is my delima. My truck is a cammed LS6 sonoma with patriot dual gold valve springs and trp pushrods. It has supposedly had a bottem end put in it due to a spun rod bearing. My problem is when i got the truck it didnt make this sound and now it does. Its like a metal to metal banging on the drivers side that goes away once the truck is warmed up a little. Only does it when I start it after it has cooled down. Any ideas what i will need to make this sound go away? Truck drives fine doesnt smoke and the sound goes away it just sounds like my piston is in a hole to big for the piston itself. Its a scary sound I have awesome oil pressure 80 psi when cold 40 when idleing warm. I dont burn oil it stays clean. I dont overheat. I just want to know what the issue may be so i know where to start looking.
sounds like piston slap (the bore is too large for the piston so it "slaps" up against the sleeve). it goes away once the pistons warm up and expand to operating temperature. its a big problem with some lsx motors, ls1 espy. nothing to worry about tho, just don't pound on it when its cold and you'll be fine 
as long as you let it warm up without beating on it it's usually pretty benign. as far as making it go away...there's really no permanent solution without fixing the bore-to-piston clearance problem. a different oil might help (search some), but that's about it.
The infamous GM Cold Start Knock (CSK). Won't hurt anything but your pride when you start it in front of your friends and it sounds like a POS. Haha! I can say this and chuckle cause my 99 Z-71 has done this since I bought it at 8Xk and its sittin on 177+K miles right now. Still runs like the day I bought it. Put your right foot on the floor and don't worry about it!!
