Final answer:
The thermostat will start to open at its rated temperature, not necessarily when the water boils, and should be fully open at this temperature to ensure maximum coolant flow and efficient engine temperature management.
Step-by-step explanation:
When discussing the operation of a thermostat in an automotive cooling system, we are dealing with a component designed to regulate the temperature of the engine by controlling the flow of coolant based on the temperature of the engine itself. Person A's claim that the thermostat will start to open when the water boils is not accurately stated. The thermostat begins to open not necessarily at the boiling point of water, but rather at the temperature for which it is rated, which may vary based on the design of the vehicle's cooling system.
Person B's assertion that the thermostat valve should be fully open when the temperature equals the rated temperature stamped on the thermostat is correct. The thermostat is designed to be fully open at its rated temperature to allow maximum coolant flow, helping to manage the engine's heat effectively and prevent overheating.
Therefore, regarding the thermostat operation, it is crucial to understand that it behaves relative to its predetermined opening temperature rating, rather than strictly when water reaches its boiling point. This ensures the engine operates within its optimal temperature range, promoting efficiency and longevity.