Just another thought, while you are leak cking, look in the radiator for a bubble trail as you ck each cylinder, at a hundred psi, it will show a leak, might even blow the cap off, if you don't take it off. Those aluminum rads, are only good for about 40 psi, then they swell the tubes, closing off any air flow over them, another good thing to give a visual, if the fins look all kinda wiggly, look carefully at the tubes. Bob