My Rio engine G4ED has a cooling system I have not encountered before. The thermostat is connected to the lower radiator hose and the upper hose is unrestricted. The thermostat has a bypass valve that is attached to the bottom. Does anyone know the purpose of the bypass valve on the thermostat? The thermostat is the same size as a small block chevy's except for the bypass valve. I'm not understanding the purpose of the bypass valve.