And the first time the engine gets hot, the patch cracks and the oil pressure behind it helps to pop it out. Does epoxy (which is plastic) have the same rate of thermal expansion as the base metal? The porous case alloy can never be fully degreased enough to get plastic to bond to it. It can be like a damp sponge that's soaked with oil, connected to a never-ending source of plenty of more hot oil. Even welding around an oil galley may not work for long, so why would you think fiber-reinforced plastic would hold better? I know it won't. Don't waste time trying. I wouldn't want to wander more than a couple blocks from home with this setup..........
Mike B. ----- Original Message ----- From: "Glen Hadley" <[EMAIL PROTECTED]> To: "Air-Cooled Volkswagen Discussion List" <[email protected]> Sent: Sunday, October 21, 2007 9:34 AM Subject: Re: [vintagvw] Repairing the VW crankcase. > The idea of backing up the epoxy is excellent. > Let me suggest something that I've used before > that works very well for a 'pressure patch'. I've > used it both on oil and on radiators: > > Mix up the epoxy, very well, and prepare the case > much as suggested. Then, mix a strong, absorbent > fiber into the epoxy, much like fiber reinforced > cement. The resulting mixture should be completely > wetted by the epoxy, with some epoxy left over, > but about half fiber by volume. It sounds crazy, > the the best fiber for this application that I > have found is to take a cheap tampon (yes, the > ones ladies use-a new one, of course!) and shred > the fiber out of it. It is super-absorbent and > will soak up the liquid epoxy, then provide a > strong reiforcement as it sets up. Some patches > I've made this way have lasted for years with > pressure applied. > > YMMV-- HTH!! > > glenh :<) > > Sharkey's Garage wrote: > >> While this method might work in the above instances because the epoxy is >> sandwiched between metal and the head gasket itself, it's only purpose is >> as >> a gap filler. Your application would require that the epoxy hold back >> oil >> that is constantly under varying pressure. Naturally it would be better >> to >> try and make the repair from the "inside" so that the pressure forces the >> repair material "into" the crack, but you appear to have no choice but to >> try and repair it from the "outside". >> >> I suppose if you could somehow "back up" the repair with something else >> that >> is bolted or screwed to the case surrounding the crack, the repair >> material >> would act more like a gasket. That way, the pressure would be partially >> taken up by whatever was backing up the epoxy. > > > _______________________________________________ > vintagvw site list > [email protected] > http://lists.sjsu.edu/mailman/listinfo/vintagvw > _______________________________________________ vintagvw site list [email protected] http://lists.sjsu.edu/mailman/listinfo/vintagvw
