I recently noticed a LOUD cold start knock that my truck appears to have developed. It only happens after the truck's sat overnight or without being run for a while. It's loud enough to have given me pause ... but it's gone in 20-30 seconds as oil gets to moving around and the vehicle commences its warm-up. Doing some reading, online, it appears that this is 'normal' for 5.3L Vortecs ... and that it isn't harmful. I'd like some confirmation of that from sources I trust, hence this post. I've also read that Seafoam may help. Now, I've never been a believer that dumping some brand of snake oil into the tank can help, but I've read enough about Seafoam to know some, here, have used it and claimed positive results. Do folks, here, think it'll make a difference? If so, what's the best way to use it for this issue? I've read about people dumping it in the tank, about them using a vacuum line to get it into the engine, about putting it in the oil ... I'm just not sure what the best way to 'feed' it to the engine might be for this issue -- if it's even worth doing. Opinions from those with this issue and/or Seafoam wanted. (Others considered, as well!) -- Surreal P.S. [MENTION=54249]RayVoy[/MENTION] and [MENTION=51590]Pikey[/MENTION] I'm particularly interested in your input as to what I should do and how I should go about it.