Suzuki Grand Vitara XL-7 Service Manual page 260

COOLANT DEGASSING TANK
The degassing tank (1) consists of a "see-through" plastic tank, a
hose and a degassing tank cap (2).
During operation, the coolant circulates inside of the degassing
tank constantly. As the coolant warms up and expands, the coolant
level in the degassing tank rises. On the other hand, it lowers as the
coolant cools down and contracts. When the pressure applied to
the inside of the degassing tank constantly exceeds the specified
value, the pressure is relieved through the degassing tank cap.
Thus, the radiator is kept filled with coolant to the desired level at
all times, resulting in increased cooling efficiency.
Coolant level should be between "FULL" (3) and "LOW" (4) marks
on the degassing tank.
Coolant should be added only to the degassing tank as necessary.
WATER PUMP
The water pump (1) is driven by timing belt (2).
The water pump can not be disassembled.
THERMOSTAT
A wax pellet type thermostat is used in the coolant outlet passage
to control the flow of engine coolant, to provide fast engine warm
up and to regulate coolant temperatures.
A wax pellet element is hermetically contained in a metal case, and
expands when heated and contracts when cooled.
When the pellet is heated and expands, the metal case pushed
down the valve to open it.
As the pellet is cooled, the contraction allows the spring to close the
valve.
Thus, the valve remains closed while the coolant is cold, preventing
circulation of coolant through the radiator.
At this point, coolant is allowed to circulate only throughout the en-
gine to warm it quickly and evenly.
As the engine warms, the pellet expands and the thermostat valve
opens, permitting coolant to flow through the radiator.
Thermostat functional spec."1.5_C (2.7_F)
Temp. at which valve begins to open
Temp. at which valve becomes fully open
ENGINE COOLING 6B-3
83_C (181_F)
95_C (203_F)