1999 GMC 2500 5.7 Knock from Hell....

Discussion in 'Engine Performance + Maintenance' started by Dylan Pope, Feb 22, 2020.

Car Parts
  1. Schurkey

    Schurkey I'm Awesome

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    Jan 14, 2018
    The Seasonally Frozen Wastelands
    First thing that comes to mind: did they use abrasive discs (Surface Conditioning Discs) to clean the gasket surfaces when they did the engine work previously? These are much like "scotchbrite" pads, but somewhat more coarse, and intended for use with power tools.

    For that matter, did the tech working in the next service bay to your engine use them on "his" engine? The abrasive particles get airborne and travel everywhere.

    Where I worked, we called 'em "cookies". They're Velcroed to a backing disc, then spun with a drill or die grinder. They're fabulously effective at removing baked-on gaskets. They're also great at removing the top layer of metal from the casting, and for spewing microscopic abrasive (aluminum oxide, I think) EVERYWHERE including into the engine, where they're carried by the oil system and destroy bearings/journals, cams, lifters, piston skirts, etc. I haven't used them for decades, in part because I came to the same conclusion that the Big Guys did: The abrasive particles are harmful to the engine.

    The AERA has a service bulletin warning of their use, as does GM.

  2. 54vicky

    54vicky OBS Enthusiast

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    Nov 10, 2019
    oakville ontario
    sorry to hear I would use stronger words if mine.

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