Thermostat Water Outlet Assembly THERMOSTAT Technologically advanced designs use bleed notches, check valves, and other methods to assist in releasing air from the cooling system.Quality construction ensures exact fit and a long, trouble-free life. Stainless steel bridge with channel-design for strength and rigidity. Stainless steel piston for longer life and more efficient operation. Brass cover and guide for heat motor piston for more efficient operation. Stainless steel mounting flange designed to properly fit and seat the thermostat in outlet casting, resulting in better performance. Channel constructed stainless steel spring frame for extra strength and durability. Stainless steel spring provides precise operating compression to quickly reach optimal engine operating temperature, resulting in better gas mileage.