When the pressure in the cooling system exceeds the maximum value, what does the radiator cap do?

The functionality of the radiator cap is crucial in maintaining an optimal pressure within the cooling system of a vehicle. When the pressure exceeds the designed maximum value, the radiator cap serves as a safety valve, allowing excess coolant to be diverted to the expansion tank. This mechanism prevents the system from experiencing excessive pressure, which could lead to potential damage or failure of various components, such as hoses or gaskets.

The expansion tank acts as a reserve for the coolant that expands due to increased temperature and pressure. By directing excess fluid to the expansion tank, the system can accommodate fluctuations in temperature and pressure without compromising the integrity of the cooling system. This operation helps to ensure that the engine remains at an appropriate temperature and continues to function efficiently.

In contrast, other options do not accurately reflect the role of the radiator cap in this context. Instead, its primary purpose is to manage pressure and coolant levels effectively, ensuring the cooling system operates safely and efficiently.