Coolant Recovery Systems: Operation
WARNING: This page does not describe the selected car, but rather 16 other vehicles, including the 1984 Plymouth Turismo, 1984 Plymouth Reliant, 1984 Plymouth Horizon, 1984 Plymouth Gran Fury, and 1984 Dodge Rampage. However, it is still accessible from the selected car via links, so may be relevant.
As coolant temperature rises and pressure in system exceeds pressure relief valve of radiator cap, excess coolant flows into overflow bottle. As engine cools and coolant contracts, a vacuum is formed in the system. The vacuum draws coolant, stored in overflow bottle, back into radiator. In a properly maintained cooling system, the only coolant losses will be through evaporation.
NOTE:
Overflow bottle captures & releases coolant according to temperature