i think there was a big step up in ICE cooling technology when manufacturers relocated the thermostat to the bottom rad hose with the top coolant rail feeding directly via top hose to rad unobstructed. The temperature sensing side of stat faces the rad and when partially or fully open feeds main coolant flow into a mixing chamber which also accepts bleeds from bypass and heater return, with its output feeding adjacent water circulating pump inlet. This configuration seems to allow better response to large changes in engine power demands, especially if stat is ECU controlled.
