My 2002 8.1 knocks when it is cold but after it warms up it goes away. Anyone else have this problem? What is the cause?? Thanks for the replies!!

CSK (Cols Start Knock) is very common on the 6.0 gas. GM's position is that is causes no long term damage and is "normal" for these engines. At first they did replace some engines, but then those came back with the same knock. I called up GM Customer Service and complained - nicely - and talked to a wonderful lady that set up an appointment at the dealer for me (actually called them on 3-way with me) so they could diagnos and document the condition. Then she called back saying the dealer confirmed it to be CSK and she sent me a GM Component Replacement Warranty good for 6yr/100,000 miles on the engine. This was just after I bought my truck used and about 3 weeks before the factory warranty ran out. I also bought GMPP Major Guard extended warranty - now my truck is pretty much covered to 88,000 miles and 2008.

Well, couldn't edit the above post so ........

My truck only does it when you first start it up. I just let it sit and "warm up" until it gets up to temp before I pull out. Had to adjust to that way of doing things as I was used to firing my old Z-71 5.7 up and pulling out. On those occasions that I am in a big hurry and just *have* to pull out right away, I keep the revs low until she gets up to temp.

My 8.1 does the same thing, has for a long time, not really a knock though, more like when you change your oil and first start it up before oil pressure starts to rise.
I have tried different types/weights of oil, from 5w30 to 15w50 and it makes less noise with 5w30, however, i generally run 15w40 during the summer and when it gets a quart low, top it off with a quart of 15w50, keep in mind that i drive in 100 plus degree temps a lot and GM doesn't recommend the use of 15w50. The noise usually stops after a minute or so though.......before i back out of the drive. Just your normal GM piston slap is what a dealer will tell you. Can't be all that bad or i'd have trashed it by now, especialy doing things like i did last weekend, when i was killing bugs on the back bumper of a white dodge pushing him along down the road, seems he could not get to 90mph as quick as i wanted to, it was a 2 lane road and he just had to soot me when we were going out of town so i helped him pick up a little speed.

Super-Pro... I havn't heard of an 8.1 with "carbon knock" that the 5.3 and 6.0 engines had, but I suppose it is possible too..What GM did for these was to take the plugs out...fill each cylinder with GM's Top engine cleaner (I'm almost positive this is the same thing as Sea-Foam is) put the plugs back in and let it sit over night..the next day, fire it up..(This cleaned the piston tops and such off) Might be worth a try on your truck if you're ambitious...

My 01 8.1 never made any racket other than out the dual exhaust...

yep same here, go away when warmed-up. after that is full throttle.

When I had my 2001 HD 4x4 6.0 it knocked all the time and I tryed a bottle of injector cleaner carbon reducer at every oil change and a bottle about mid way between oil changes and the knock went away.I told a friend of mine as he had the same problem to try what i did and his knock went away also. Dont worry about engine damage as my brother-in-law has a 6.0 knocker and he has over 140,000 miles on his truck and it runs just like he bought it.

NOT A PROBLEM?

BETTER CHECK THIS WEB SITE OUT!

WWW.PISTONSLAP.COM (http://www.PISTONSLAP.COM).

THIS IS WHY I SOLD MY 99 (SLAPING) SILVERADO,

All more reason to have nice sounding loud exhuast on the truck.

Knocking that you hear is mostly due type of piston(hpyercrap) used and wrist pin type(i.e. non-floating type) Piston shinks more when it cool so the piston has "extra clearance for a short while until warm when it expands. plus non floating wrist pin lends itselfs to making the piston "rock" which you hear as knock.

Ah if we only could have all the bells and whistles, forged stroker cranks, oliver rods, mahle forged pistons with the latest in coating and gas port technology. :ro)

oh well, could be driving a ford right now, and have no power at all, wheres the class-action lawsuit for that?? ):h

I like 8100hammer's solution..........loud dual exhaust, couple that with the radio turned up............what was it you said you were hearing?