What is the purpose of expansion plugs (frost plugs) in an engine block?

Expansion plugs, commonly known as frost plugs, serve the critical function of sealing off openings that are created during the manufacturing process of the cylinder block. These plugs are inserted into holes left in the engine block for various reasons, such as providing access for machining processes during manufacturing.

Over time, as the engine operates, it can be exposed to freeze-thaw cycles, which can create internal pressures. The primary role of these plugs is to prevent coolant leaks by filling in these openings, thus maintaining the integrity of the engine's cooling system and ensuring that the engine operates effectively without the risk of losing coolant. By sealing these openings, expansion plugs help protect the engine from potential damage that could occur due to fluid loss or contamination.

The other choices do not accurately describe the role of expansion plugs. They do not enhance engine performance, prevent overheating directly, or support the weight of engine components. Instead, their main purpose is specifically related to sealing and maintaining the structure of the engine block.