1972 Mercury Marquis Cooling System Problem

[ThomasBorchers]

Hello,

I recently bought a 1972 Mercury Marquis. Runs great but I have a problem with the cooling system.

I can drive on the freeway, then in the city with stop and go traffic.... no problem. The overheat light is not glowing and it runs around 185°F. But... when I shut of the engine, the water is going out the overflow. So long, until the water level is half of the radiator.

But I can't hear, that it is boiling... I cleaned the sytem recently.

I have the correct 13 lbs cap but I know, that someone has removed the thermostat.

So my question is, why the water blows out of the system after shutting of the engine after 3 or 4 stops.

Kind regards

Thomas