Subaru 2002 Impreza Service Manual page 180

COOLING CIRCUITS
Coolina
B: TURBO MODEL
The cooling system operates in three different phases depending on the temperature of the engine
coolant.
0
1st phase (thermostat closed)
When the engine coolant temperature is below 76°C (169"F), the thermostat remains closed. The
coolant flows through the bypass and heater circuits.
This permits the engine to warm up quickly.
0
2nd phase (thermostat open)
When the engine coolant temperature is above 76
-
80°C (1 69
-
176"F), the thermostat opens.
The coolant flows through the radiator where it is cooled.
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3rd phase (thermostat open and radiator fan operating)
When the engine coolant temperature sensor sends a signal indicating a temperature above 95°C
(203°F) to the ECM, it causes the radiator fan (or fans) to operate.
When the engine is stopped after high-speed operation, vapor produced in the turbocharger cool-
ing section flows from the coolant filler tank to the reservoir tank where it condenses back into wa-
ter.
Water is then absorbed by the coolant filler tank as the engine cools down.
C..
. .
T'
I
(1) Radiator
(2)
Engine coolant reservoir tank
(3) Thermostat
(4) Throttle body
(5) Heater core
(6) Coolant filler tank
(7) Turbocharger
NF0483
(8) Oil cooler
(9) Cylinder head RH
(1 0)
Cylinder jacket RH
(1 1 ) Cylinder block RH
(12)
Cylinder block LH
(1 3) Cylinder jacket LH
(1 4) Cylinder head LH
CO-4