Liberty 2WD L4-2.4L VIN 1 (2005)
Coolant Reservoir: Description and Operation
COOLANT RECOVERY CONTAINER
COOLANT RECOVERY NON-PRESSURE SYSTEM - 2.4L
DESCRIPTION
This system works on the principal of a closed and completely deaerated system using thermally generated pressure. The bottle acts as a reserve
coolant source to keep air out of the system but must have a specified minimum amount of coolant in the bottle at all times. The expansion and
contraction of the coolant in the pressurized closed coolant loop allows the reserve bottle to accept and give up excess fluid via a hose from the
radiator neck. It provides:
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A non-pressurized reserve coolant tank volume for expansion and contraction of coolant.
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A pressurized cap on the radiator. This keeps the main loop of the cooling system at an elevated operating pressure and prevents coolant boiling at
lower temperatures. It is the highest point in the 2.4L.
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Reserve coolant is included in the non-pressurized tank in enough quantity to account for minor leaks and evaporation or boiling losses, and to
keep the return line back to the radiator full at all times. Failure to do so could allow air to be sucked back into the radiator as the engine and
engine coolant cool down and the coolant volume contracts.
OPERATION
As the engine warms, the coolant in the closed system expands and builds up pressure against the radiator pressure cap. When pressure, on occasion,
exceeds the rated pressure of the cap, the coolant forces the lower seal open and allows the expanded coolant volume to flow into the hose leading to
the external coolant bottle. The bottle accepts the expanding fluid. This allows the main circuit to remain full of coolant with no air. Then, when the
engine is in an environment where it is transferring less heat, or it is shut off and starts to cool down, the coolant also begins to contract. As it
contracts, it begins to create a vacuum in the enclosed space of the radiator cap and filler neck that starts to draw coolant back into the radiator from
the external coolant bottle. The coolant flows into the radiator through a bleed hole in the lower area of the radiator pressure cap. This method of
operation requires that the bottle have a minimum amount of coolant in it at ambient temperatures, as it would be highly undesirable for the radiator
vacuum to suck in air from a depleted coolant bottle.
The advantage of the coolant recovery bottle is cost. The system is much less sophisticated then a pressurized bottle system but puts a premium on a
successful coolant fill that contains no air. The coolant bottle cannot be allowed to run dry. If it does, air could be sucked into the system, the water
pump could cavitate and the cooling system be destroyed or severely damaged.