Engine cooling system air venting arrangement

An air venting arrangement for the cooling system of an automotive type engine that includes a radiator coolant inlet connected by tubing hosing to the engine, the engine having a coolant outlet housing mounted to the engine in communication at one end with the engine internal coolant flow passages and the other end connected to the hosing for flow of hot coolant to the radiator, the outlet housing containing a thermostat horizontally movable to open and close the outlet in response to coolant temperature changes from a predetermined level,

• the housing having a horizontally oriented inlet portion sealingly receiving the thermostat therein and a horizontally oriented outlet portion connected to the hosing, and a housing connecting segment connecting the portions and extending in a diagonally upward direction from the inlet portion to the outlet portion, a bypass passage extending through the wall of the housing diagonally upwardly from an inlet point adjacent the uppermost outer diameter of the inlet portion containing the thermostat to a point within the connecting segment at a location vertically above the inlet point to the passage to assure a bleed of air through the passage from the coolant bypassing the thermostat, and check valve means in the bypass passage movable by gravity to a position opening the bypass passage in response to the presence of an air pocket in the bypass passage to vent air from the engine to the radiator and movable to a closed sealing position in repsonse to the force of coolant flow against the valve to prevent flow of coolant to the radiator through the bypass passage.