If you're talking gaskets, I would suggest not doing that. It acutally makes things harder to seal, and was an old "trick" that people used to do just to skip the cleaning and prep process, which is something my dad used to call "half assing it!"
If you want to make sure something does not leak, remove the old seal (ALL OF IT) clean, grind, scrape, wire brush, etc., whatever you need to do to get the mating faces PERFECTLY CLEAN! Then clean again with acetone or whatever your favorite degreaser is. Then clean it again with degreaser. Then maybe clean it again. Get the hint?! Next, depending on the application I will typically use purple Permatex, or Indian Head Permatex, or, whatever the correct gasket sealant is for the application. Follow the directions for application. Lastly, bolt up the appropriate pieces and torque to specs.
By following these steps you are actually making a better gasket installation than was done at the factory, as all factory installed gaskets were done dry, with no sealants. Cork gaskets should seal dry, but the installation of Permatex products greatly enhances this, and makes up for some of the imperfections that may have occurred over the years. Also, the sealants will "help" if for some reason the surfaces are not perfectly clean, or a drop of oil runs across a surface and you don't notice it. Regardless, if you take your time, this is the best way to seal things.
Last edited by gitractorman on Tue Mar 12, 2013 6:35 am, edited 1 time in total.