37 Cadillac-New rebuild, foaming antifreeze

[boothandco]

Anyone got any ideas on what could be causing this?  It's got good compression, install was done by good mechanic, but If I drive it Even 2 miles, it foams half of the antifreeze out of the overdraft tube.

[Bobby B]

Did you bleed it to get some air out? It's easy to overfill the Flathead radiator. You don't need to fill it to the top because it WILL overflow until it seeks the correct amount of coolant. If you think you didn't overfill it, a pressure check of your cooling system, and/or a compression check, would be in order. Keep us Posted. Good Luck!
                               Bobby

[LaSalle5019]

What I would do to verify I don't have a head gasket leak or crack in the block, both of which can allow cylinder pressure to enter the cooling system, is apply air pressure through the spark plug hole in each cylinder and listen for any bubbling with the radiator cap off. You can typically do this with a compression tester and adapt an air air hose in place of the gauge.  That will at least eliminate one area of concern.
Scott

[James Landi]

Another approach to Scott's diagnostics is to simply fill the radiator with coolant ALMOST to the top.  As he mentioned, a minor leaking head gasket or crack in the cylinder head or worst yet the compression side of the engine block will show as a steady stream of bubbles coming up through the engine coolant in the almost filled radiator.  ALas, I've had this occur, and the engine ran very well because the leak was relatively insignificant with respect to the compression in the cylinder.  Let's all hope and pray that you DON"T have that problem, and it's simply that your coolant system is not entirely filled .  James