Yea, you have nothing to loose, putty it up, or use a sealer on it. If the first sealer don't work, try another. I know that the JB weld will work. On tractor engines I do drill both ends of the crack so it does not spread, v it out, and spread it on. The sand paper sounds like a great Idea, I put duct tape over it to texture it (remove it when dry), same idea as the sand paper.
KB
