Page 384 of 1082
02-38
Engine oil
Coolant
Coolant and oil flows ▶
Cylinder head
Cylinder block water
jacket
Coolant pumpCoolant pipe
Thermostat
Supply line to cylinder head
Oil pumpSupply line to PCJ
Main bearing
Oil filter assembly
Page 427 of 1082

08-4
Problem Possible Cause Action
Coolant
level is too low
Coolant
temperature is
too high
2. INSPECTION
Leak from the radiator
Leak from the coolant auxiliary tank
Leak from the heater core -
-
-
Leak from the water inlet cap
Leak from the thermostat housing -
-Reconnect the hose or replace the
clamp
Change the hose -
- Leak from the coolant hose connections
Damaged coolant hose -
-
Change the gasket
Change the water pump -
- Leak from the water pump gasket
Leak from the water pump internal seal -
-
Tighten the bolts to the specified
torque
Change the cylinder head gasket -
- Incorrect tightening torque of the cylinder
head bolts
Damaged cylinder head gasket -
-Change the water inlet cap gasket
Change the thermostat sealing -
-
Coolant leakage (Coolant level is low)
Improper coolant mixture ratio
Kinked coolant hose -
-
-Add coolant
Check the coolant concentration
(Anti-freeze)
Repair or replace the hose -
-
-
Defective thermostat
Defective water pump
Defective radiator
Defective coolant auxiliary tank or tank
cap -
-
-
-Change the thermostat
Change the water pump
Change the radiator
Change the coolant auxiliary tank or
tank cap -
-
-
-Change the radiator
Change the coolant auxiliary tank
Change the heater -
-
-
Cracks on the cylinder block or
cylinder head
Clogged coolant passages in the
cylinder block or cylinder head -
-Change cylinder block or cylinder
head
Clean the coolant passage -
-
Clogged radiator core -
Replace the sensor or repair the
related wiring - Improper operation of cooling fan -Clean the radiator core -
Defective temperature sensor or faulty
wiring -Replace the cooling fan or repair the
related circuit -
Page 431 of 1082

08-8
3. CAUTIONS
If 100% of anti-freeze is added, the water pump vane can be damaged and thermal conductivity can
be decreased resulting in poor circulation in the cooling system which leads to overheated engine.
Use of non-recommended coolant could cause damage to the cooling system and overheating of the
engine.
Opening the coolant reservoir cap while the engine is running or hot can cause burns by hot steam o
r
water.
To open the coolant reservoir cap, wrap the cap with a wet towel or thick cloth after the engine is
cooled down sufficiently.
If cool water is added to the heated engine, the engine or radiator can be deformed.
The anti-freeze in the coolant can damage the painted surface, so avoid the contact of the coolant to
the painted body.
The anti-freeze and water should be mixed in proper mixture ratio. Never add only water when
adding coolant.
If the anti-freeze content is too low, the coolant can be frozen while the engine can be overheated if
anti-freeze content is too high. -
-
-
-
-
-
-
-
Page 432 of 1082
08-92112-01
4. LAYOUT
Water Pump Assy
Bolt
Water Pump Pulley
Bolt
Thermostat Assy
Bolt
Coolant Outlet Port Assy
Bolt 1.
2.
3.
4.
7.
8.
9.
10.Coolant Pipe Assy
Bolt
Bypass Hose
Clamp
Deaeration Pipe Assy
Bolt
Bolt Deaeration Hose
Clamp 11.
12.
13.
14.
15.
16.
17.
18.
Page 435 of 1082
08-12
Water pump
The water pump is driven by the engine drive belt and supplies
the coolant to each area of the engine.
Coolant reservoir
Thermostat
When the engine coolant
reaches 90℃, the thermostat
starts to open (fully open at
100℃) and lets the coolant
flow to the radiator to maintain
the engine temperature.
1. OVERVIEW
The coolant system is to keep the engine temperature stable.
2. COMPONENTS
Page 437 of 1082
08-14
3. COOLANT FLOW DIAGRAM
Heater
return Water pump
Thermostat
Bypass
Page 438 of 1082
08-152112-01
Coolant outlet port
to radiator
to water pump (bypass)
to cabin heater
to coolant reservoir
Coolant temperature
sensor mountinh boss
from cylinder head
Gasket A:
B:
C:
D:
E:
F:
G:
Coolant outlet port
Page 483 of 1082
15-18
6) Cooling Fan Control
(1) Overview of Cooling Fan and A/C Compressor
The cooling system maintains the engine temperature at an efficient level during all engine operating
conditions. The water pump draws the coolant from the radiator. The coolant then circulates through
water jackets in the engine block, the intake manifold, and the cylinder head. When the coolant reaches
the operating temperature of the thermostat, the thermostat opens. The coolant then goes back to the
radiator where it cools. The heat from automatic transaxle is also cooled down through the radiator by
circulating the oil through the oil pump. There are two cooling fans (180W+120W) in G20DF engine. ECU
controls the electric cooling fans with three cooling fan relays to improve the engine torque and air
conditioning performance.
(2) Components
Refrigerant pressure
sensorCoolant temperature
sensorG20DF Engine
ECURelay box in engine
compartment
A/C compressorCooling fan moduleT-MAP sensor