This is a metallic valve. It contains a liquid which automatically converts into 60°C to 65°C. It is fixed in the water exhaust passage of the water cooling system. This valve remains shut and. it does not allow the engine water tc enter back the radiator till the temperature of the engine is low. The moment the engine’s temperature rises above the normal, this valve opens and the hot water of the engine starts going into the radiator where it gets cool.