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  1. #1

    Default Advice? Knocking

    i have a 2000 silverado that i bought about a month now with 102k. i had just changed the oil about a week ago. then about 3 days after that it started knocking, but it started to get cold too, with 10+ inches of snow.
    is this piston slap? if so what can i do to fix it?

    how many of you guys recommend seafoam? is it really safe?

  2. #2


    no my friend put that in his skylark and it blew up a week later

  3. #3

    Join Date
    Feb 2008
    Red Wing, Minnesota, United States


    never had a problem with seafoam, nor have i ever heard of anyone on this sight having a problem with it, just search seafoam, there have been TONS of posts about it
    99 K1500 Suburban LT "THE BEAST"
    Hypertech III, K&N, true dual

  4. #4


    used it on my truck. works great!

  5. #5


    Is this a knock or a rattle when cold? These engines have zero piston skirts and from the first year they came out at 20k plus miles there was a large number of cold engine piston rattles. The condition doesn't seem to effect longevity but it does sound terrible for the first several minutes of operation. It was discovered that removing carbon from the piston did reduce the noise for a short period of time. If you have a knock that is a different issue, a knock will usually get worse as the engine gets warmer while the rattle I refer to will go away as the engine warms up.

  6. #6


    If it only happens when the eng is cold it is common and doesn't effect the eng. Like the previous post it is a carbon build up issue.

  7. #7


    also common in the newer gen engines is oil pump drive noise, by your desciption, i would guess put 10w30 in motor instead of 5w30. try to stick to the 5w, as this will help quiet the noise quicker. many of these trucks around here have the common noise, mine included, since 30k. running strong at 165k synthetic always since 30k quieted it down. good luck.

  8. #8


    thanks alot guys, much appreciated

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