cletis there are a lot of really good suggestions here. I think this is what I would do. drill the ends of the crack to keep it from spreading. Then I would drain the cooling system including the block. Then I would cap off the upper hose outlet. Attach shop vac to the Lower hose and see just how much air you suck through the crack. If it is a lot then you will need a smaller source of vacuum. If it only sucks a little then fine. I would then mix up some epoxy and apply using the vacuum to help "draw" the epoxy into the crack. Good luck and let us know what you end up doing.
