The water outlet is the connection between the engine and the upper radiator hose through which hot coolant from the engine is pumped back into the radiator. The water outlet has been called a gooseneck, elbow, inlet, outlet, or thermostat housing. Generally, it covers and seals the thermostat and, in some cases, includes the thermostat bypass.
Inspect the coolant outlet (thermostat) housing for leaks or damage. Aluminum housings often suffer electrolysis damage.