a halftrack thermostat is never closed. the thermostat does not block the flow as most modern engines are setup, the halftrack thermostat has a sleeve that slides in another part of the housing supplying the pump with water circulated through the engine or when it is warmed up through the radiator. using a modern thermostat would block flow when cold (which is ok) but when warmed up instead of being directed through the radiator it would both recirculate through the engine and go through the radiator which may cause overheating problems. a modern engine is one way in and one way out through the thermostat. a halftrack engine is one way in and two ways out.
