Thanks to all for your ideas. After replacing the thermostat with a heavy duty one, replacing the old radiator cap, the bottom hose(replaced a molded with a flex hose) to get more stability under pressure, It appears that the problem has been solved. Once again I learn that you never, never, never put old stuff back in. Just replace it and save yourself the time of re-doing it. Zak [Non-text portions of this message have been removed]