Cool/Heat: Will the expansion tank empty?

[Hawklover]

On a Studebaker Avanti...........if one removes the heater hose (manifold end) from the line that feeds the inlet of the heater control valve, will this trigger the expansion tank to empty?

Thanks

[WCP]

Yes. Drain off some from the radiator to drop the level to that of the mid-manifold. With the thermostat closed, the surge tank will slowly drain or bleed into the manifold.