I have an engine noise in my recently purchased used 2000 Chevy Silverado. I have the 5.3 engine with 126,000 miles. When first started after setting overnight or all day while at work, I can hear a dull knock for about 10 to 15 seconds. If you drop it into gear, (automatic) and leave at idle, it sounds very much like a diesel engine knock. It carries 60 psi oil pressure, (dash gauge) from the get go. I never here the noise any other time. The engine runs good, doesn't smokeand doesn't seem to use oil. Could I possibly have a lifter that is bleeding down? If so does anyone know of any oil additive that might solve this problem or is it best to bite the bullet and replace the lifters.
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mine has done it since i bought it around 118,000. there are a lot of articles on this if you google it or even search the forum. it's piston slap due to gm changing the way their assembly line manufactures pistons to fit individual pistons. they used to match each piston to each cylinder, but eventually they just started mass producing pistons that were the exact same size....for some reason they don't all match up exact with the cylinders they are placed into because of this and a lot of our trucks get piston slap because of it. after enough oil gets to the top of the engine it stops the noise...gm says it's not a big deal.
they used to match each piston to each cylinder, but eventually they just started mass producing pistons that were the exact same size.
Where did you read that? That doesn't even make sense. If that were the case, how would you ever buy a set of pistons to rebuild a motor? Do you have any idea how long it would take to produce motors if you had to custom make every piston for a specific cylinder? Of course they're all the same size.