Things have been just dandy until this weekend, when I started the Yukon up after sitting all night in the garage. What I heard horrified me; it sounded almost like a diesel for a few seconds!! Now it's happening almost everytime I start it up after it's had a good cooldown period. I'd heard GM had this problem with some of the newer smallblocks, but I thought it was mostly 2000-2001 models? Anyone else still having this problem with their 5.3??? What is GM doing about it?

somw would call it piston slap

ALL the Vortec 8 cylinders are included in GMs bulletin about valvetrain rattle or tapping.

GM is not doing anything about it as there is no "problem". The motor is made with such close toleranaces that under cold conditions there are many components that "tick" or "tap" There is no contact being made with any components just with carbon build-up or valve guide "stick".

Hope this explains it.

No problem huh? Then maybe you should read this....

http://www.pistonslap.com