Expansion tanks accommodate coolant volume changes due to temperature fluctuations within a vehicle’s closed cooling system. Typically constructed of polyamide or polypropylene, these pressurized reservoirs maintain system pressure and prevent air ingestion. Integral baffles within the tank de-aerate coolant, minimizing cavitation and corrosion. Level sensors or vent ports may be incorporated for monitoring or pressure regulation. Expansion tanks are commonly located in the engine compartment and are specific to vehicle make and cooling system design.