What action involves applying pressure to the radiator cap?

The action that involves applying pressure to the radiator cap is associated with cooling system pressurization. In a vehicle's cooling system, the radiator cap plays a crucial role by maintaining the system's pressure. When the engine heats up, the coolant temperature rises, and the liquid expands. The radiator cap seals the cooling system, allowing it to build up pressure, which in turn raises the boiling point of the coolant. This high pressure prevents the coolant from boiling excessively and helps maintain an efficient engine temperature.

Pressurization is essential for effective heat transfer and preventing overheating, which can lead to engine damage. If there were no pressure, the coolant would boil off at a much lower temperature, leading to the risk of engine failure. Therefore, the interaction between the radiator cap and the cooling system is fundamental for ensuring that the system operates correctly under varying engine conditions.