Jw, it has a 4 lb pressure cap and doesn't appear to be leaking, but I guess if it's just drawing in air you wouldn't see anything. Would that still cause the rolling boil that I had last Saturday when the water was boiling out of the overflow reservoir?

1950 Chevrolet 3100 (Ol' Roy)

1939 Packard Standard Eight Coupe (The Phantom) | 1956 Cadillac Coupe de Ville (The Bismarck) | 1964 Ford Galaxie 500 coupe |1966 Ford Mustang (Little Red) | 1969 Pontiac GTO (The Dishpit) I 1979 Ford F-100 | 1976 Ford F-150 (Big Red) | 1995 Ford F-150 (Newt)