Expansion Tank
Expansion Tank
When the engine is heated, the coolant expands to fill any available space (usually in the radiator ). Before the introduction of coolant expansion tanks, the excess coolant was forced out of a vent tube and on the ground. The expansion tank collects the coolant so that when the engine cools off, the resultant vacuum sucks the coolant from the tank back into the radiator .
An expansion tank is one part of a complex overall car cooling system that’s designed to keep the engine operating at exactly the right temperature.
In the sealed cooling system that’s present on most cars, it is partially filled with air. The air in the expansion tank provides a ‘cushioning’ effect that allows the heated coolant to expand without causing the cooling system to fail. This is to prevent the system from becoming over-pressurised as the coolant heats up and expands.
An expansion tank is designed so there is space in the tank for the coolant to expand. If an expansion tank is overfilled it will discharge coolant when the system is at operating temperature.
