I'm posting this because everything I have found about knocking sounds appear to be related to RPM or load. I have a 04.5 LLY with 42k. I have a noticable knocking sound that occurs right at 190 f as the engine is warming up and lasts for only a short period of time. Before that temp or after that temp there's no noise. Also it doesn't happen all the time maybe several times a month but is always at that temp. The dealer says the top end is dirty and needs to be cleaned??? They could correct this by injecting a cleaner into the cylinders and letting it set over night for $100. Sounds like a load of BS to me. Has anyone else notice this sound at this temp?

Thanks

have 04 with 15000 miles bought it new had noise since it was new took it back 3 or 4 times changed different things now dealer give me a report from gm they say ALL duramaxs does this and it is normal and dont try to fix it that a new engine would not fix it