Liberty 4WD V6-3.7L (2009)
Coolant Reservoir: Description and Operation
Operation - Pressure System
PRESSURE SYSTEM
As the engine warms, the coolant in the closed system expands. The pressurized bottle accepts the expanding fluid. Then, when the thermostat opens and
a high demand for coolant is placed on the system, the pressurized surge tank side of the bottle can supply the temporary additional volume of coolant
demanded by the system. Once the water pump catches up with the flow demand, the tank returns to equilibrium. A separate compartment in the bottle
accepts the overflow coolant which is then drawn back into the primary side of the bottle when the engine and coolant cool down
The advantage of the pressurized system is that any excess air in the cooling system is routed to the top of the bottle via a vent hose at the thermostat
housing to the bottle. This air accumulates at the top of the pressurized volume in the bottle (the highest point in the system) and is forced out of the
system through the pressure cap. This keeps the system properly deaerated and maintains pressure in the cooling system to prevent water pump
cavitation.
