With the overflow plastic jug a new radiator cap I drove 15 miles and later 15 miles back with no problem. Whoever said start with the simple things was right--what I should have done right at the start was the thermostat the cap and the overflow jug. Now I know-- but every case is a mystery until you track it down. I hope I have it solved at last.
Happy Thanksgiving everyone and thanks for all your help.
