Piston slap? Wasn't there a big stink about it years ago? It's from the piston skirt hitting the cylinder wall due to too much clearance. The noise stops once the piston expands to operating dimensions. I'm not sure if there's anything you can do about it.
yea it sounds more like the piston skirt prob. the oil pressure jumps up as soon as it fires up only weird thing is it only started doing it about a yr ago ive had the truck since 07 and it only had 50,000 miles on it i dont know i may just wait till it pops and try to find a 6.0 to put in it
Mine does the same thing on start up. Usually worse when it is cooler outside. Knocks for about 20-30sec and then I'm good to go. It worried me for a while and then after reading the forum, I found out I was not the only one with the same issue. I just let it warm up and the go.
I have or should say had it too..I went to dealer and said this is not normal at any rpm, or weather an engine is cold or hot.I have a 2011 silverado with a 6.2 , Mine knock for about 5-10 minutes and I live in florida so how cold can an engine be here.Anyways they were going to replace cam and lifters per GM..but i knew that was a joke answer.They pulled the heads and guess what.#8 cylinder was completely scored.So they ordered a new crate engine to put in my truck.Dont let anyone ever tell you that engine knock is normal..its usually only one or 2 cylinders that have the cold engine knock.So when someone tells you that noise is normal tell them that ,that must mean the other cylinders are running abnormal
I just joined the forum, and I see that it's been a while since you posted this problem with engine knock at start up, but if you still own the truck this will help. I installed a Bosch oil filter that has a check valve in it. It keeps the oil up in the engine where it needs to be at start up. Knocking since new, the noise is virtually gone on my 01 Suburban with 230K on the 5.3 engine. The check valve is not 100% though, and if the truck sits for a couple days the oil eventually seeps back into the pan and the knock returns. But if you drive it today the knock will not be there tomorrow when you start it up.
I recently told a friend who own an 01 GMC Sierra with the 5.3 and had the same noise. He put the Bosch filter in and told me that the knocking ceased in his truck as well. When I first bought the truck new I took it to the dealer and asked about the knocking noise. They printed up a memo from GM stating that the knocking noise was "normal". Can you believe that? I still have that memo somewhere. Go to CarComplaints.com and see how common this problem is, though.