on cold start up my 8.1 bangs like a diesel for about 2-3 minutes and dealer said it is a problem w/ carbon accumulation on top of pistons. said they were cleaning pistons in beginning but not anymore because it just builds up again fast. is this detonation? any opinion if it is damaging my motor? I have heard there is litigation now in fed court as to pistion slap for pre 2003 motors. Is this pistion slap? Help!!!

My 2003 8.1L also sounds terrible on start-up and is eating some oil.

Doing an oil consumption test now and keep complaining to GMC about the clatter.

Good news is that the truck has plenty of pulling power.

mine is using excessive oil also, but still plenty of power. still want answers & help thnx!!

sounds like they are bsing you,if carbon on top of the pistons was causing noise you'd here it all the time plus a stock motor is going to have at least .060 thousandths clearence between deck surface in the head if not more,there would have to be a TON of carbon!!! I would guess piston slap,once the skirt expands and clearence tightens up the noise woiuld go away,Smitty

Seems to me there was an issue with the piston slap in the 6.0 and 8.1's for a while. Something about metric sized pistons and rings with a conventional standard bore that ended up with irregular clearances and a little cold slap.

piston slap,
had a tahoe that did the same thing ,they gave me a little booklet on the problem saying it was normal and that no abnormal wear and tear on the motor would accure BS!

Same here with my 454 Suburban, "Not a durability issue".
I *****ed and complained and got nowhere. First they gave me carbon build-up story, then told me I needed a different oil filter of all things.

It's a bunch of crap. Too much clearance someplace, plain and simple. GM junk in opinion, I'm done with GM.

Yup, you got piston slap. Carbon cleaning helps until it builds up again. I tried Mystery Oil with every fill up and that helped too, but a short term fix. Got too expensive per gallon to keep that routine up. Long highway runs also help clean out carbon.

I have 112K miles on my 2001 5.3 Yukon. Mine chatters like a banshee on cold startup but I use no oil and runs as strong as the day I bought it new. So, I tend to beleive if you keep up your maintenance it's not a durability issue. Just tell folks you have a diesel when you crank it in the AM.

I have a 2002 6.0L gas and reported it to the dealership while under warranty. I then contacted GM customer service directly. I did end up getting an extended warranty out of them for the engine only for 7 years 100K miles I think? You might want to check out the other forums relating to pickups. I believe I found the contact information on one of them...fullsizechevy.com or pickuptruck.com. My truck doesn't burn a drop of oil even on long trips pulling the boat around. I've heard it's a matter of engineering as they made the engine with lots of play and or cheap piston skirts...apparently only a couple of the skirts are coated to avoid this "knock" sound we've all experienced. All in all I could not be happier with my truck though!

thnx for all the ideas/suggestions and any others are greatly appreciated!!! I run mobile 1 and the dealer also told me to use ac oil filter to solve the problem. Like that would do it, but I tried, but no change. I am not afraid of the motor and it runs and pulls like new. I actually love the motor except for the sound at start up. The vehicle is the best I have ever had and would buy a dozen more. I would rec to anyone. Is anyone scared of the potential carbon build up?