34 Ford Radiator Leak?

[The Art Doctor]

Water expands about 3% when heated to around 180*F. This is why in old cars "it will find its own level". If you just leave it alone the excess will push out and what remains is 3% less than over full. If you keep filling it up it will keep pushing that 3% out. New cars do this too, that is what the recovery tank is for. In a closed pressurized system when it cools it creates a vacuum that sucks the coolant from the recovery tank back into the radiator.