Question 149Motor Plants - QMED

The correct answer is B) allow for an increase in water volume as the engine warms up. The expansion tank in a diesel engine's closed cooling system is designed to accommodate the increase in water volume that occurs as the engine warms up and the coolant expands. As the engine heats up, the water in the cooling system expands, and the expansion tank provides the necessary space to absorb this increased volume without building up excessive pressure in the system. This helps maintain a constant head (pressure) on the cooling system. The other options are incorrect because they do not accurately describe the primary purpose of the expansion tank. Reducing water temperature (A), reducing water turbulence (C), and providing an air-cushion (D) are not the main functions of the expansion tank in a diesel engine's closed cooling system.