Coolant Reservoir: Description and Operation

Figure 2-Coolant Pressure/Recovery Bottle:

The coolant bottle consists of two chambers. The pressure chamber keeps the coolant free of trapped air, provides a volume for expansion and contraction, and provides a convenient and safe method
for checking and adjusting coolant level at atmospheric pressure. It also provides some reserve coolant to cover minor leaks, evaporation or boiling losses. The overflow chamber allows coolant recovery in case of an overheat. An overflow hose connects the pressure chamber to the overflow chamber.

NOTE: Coolant will normally be in the pressure chamber side of the coolant bottle. The overflow chamber should normally be empty