Page 247 of 828

08-4
2. INSPECTION
Problem Possible Cause Action
Coolant level is
too low- Leak from the radiator
- Leak from the coolant auxiliary tank
- Leak from the heater core- Change the radiator
- Change the coolant auxiliary tank
- Change the heater
- Leak from the coolant hose
connections
- Damaged coolant hose- Reconnect the hose or replace
the clamp
- Change the hose
- Leak from the water pump gasket
- Leak from the water pump internal
seal- Change the gasket
- Change the water pump
- Leak from the water inlet cap
- Leak from the thermostat housing- Change the water inlet cap
gasket
- Change the thermostat sealing
- Incorrect tightening torque of the
cylinder head bolts
- Damaged cylinder head gasket- Tighten the bolts to the specified
torque
- Change the cylinder head gasket
Coolant
temperature is
too high- 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
- 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 - Clean the radiator core
- Improper operation of cooling fan - Replace the cooling fan or repair
the related circuit
- Defective temperature sensor or
faulty wiring- Replace the sensor or repair the
related wiring
Coolant
temperature is
too low- Thermostat is stuck open - Change the thermostat
- Improper operation of cooling fan - Replace the cooling fan or repair
the related circuit
- Defective temperature sensor or
faulty wiring- Replace the sensor or repair the
related wiring
Page 248 of 828
08-51520-00
1) Coolant Level Check
Park the vehicle on level ground and apply the parking brake. Stop the engine and wait until it is
cooled down.
The coolant level should be between the MAX and MIN mark on the coolant reservoir.
Check the coolant level. If the level is below the “MIN” mark, immediately add coolant. 1.
2.
Scalding hot coolant and steam could be blown out under pressure, which could cause
serious injury. Never remove the coolant reservoir cap when the engine and radiator are hot.
Avoid any direct contact of the coolant to the painted body of the vehicle. -
-
MAX
MIN
Page 249 of 828
08-6
2) Leak Test
Release the pressure in the system by
loosening the pressure cap of the coolant
reservoir slightly. Then, remove the pressure
cap completely. 1.
Never open the cap until the coolant
temperature becomes under 90℃ to
prevent any burn.
Add the coolant so that the coolant level is
between MAX and MIN mark on the
coolant auxiliary tank.
Connect the tester to the tank filler and
apply pressure (1.4 bar).
Check all the coolant hoses, pipes and
connections for leaks when the pressure of
the tester drops, and replace or tighten, if
necessary. 2.
3.
4.
3) Thermostat
Immerse the thermostat into the water. Heat
the water and check the valve opening
temperature.
Valve opening
temperature 90±2℃
Page 250 of 828

08-71520-00
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 or 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 251 of 828
08-8
Oil filter module
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.
Water pump
The water pump is driven by the engine drive belt and
supplies the coolant to each area of the engine.
Coolant reservoir
Long life coolant is used.
1. SYSTEM DESCRIPTION
1) Overview
Water pump
Impeller vane Sealing
Page 252 of 828
08-91520-00
Electric fan
Circulates the fresh air forcibly to exchange
heat with the radiator core fin.
Radiator
Releases heat through fins and cools down the hot
coolant as the coolant passes through the tube of
the radiator core.
Coolant temperature sensor
Measures the coolant
temperature and sends the
result to the engine ECU.
Page 265 of 828
10-4
Glow plug control unit
(GCU)
1. OVERVIEW
The pre-heating system for D20DTR engine has the glow plug to the cylinder head (combustion
chamber), and improves the cold start performance and reduces the emission level.
The pre-heating resistor (air heater) is used to heat the intake air.
This enables the diesel fuel to be ignited in low temperature condition.
The ECU receives the information such as, engine rpm, coolant temperature, engine torque, etc.,
through CAN communication during pre-heating process; and the pre-heating control unit
controls the pre-heating, heating during cranking and post-heating by the PWM control.
Glow plug
Glow indicatorEngine ECU (D20DTR)
Page 268 of 828

10-71413-00
4) Operation
Glow plug is installed in the cylinder head. It enhances the cold starting performance and reduces
the exhaust gas during cold starting.
(1) Operation
Duty control area:
Between 5 and 100%
Frequency: 20 Hz
Duty ratio = (RMS voltage)²
(Battery voltage)² 1.
2.
3.
Pre-Glow: Step 1 ▶
If normal communication with the ECU is established 2 seconds after the power is supplied to the
IGN terminal from the battery, the GCU supplies the battery power to raise the temperature of the
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47009b008f008c0047008c0095008e00900095008c0047006c>CU before starting.
Pre-
heatingCoolant
temperature-30°C -25°C -20°C -10°C -5°C 0°C 20°C
Operating time
28 s 25 s 15 s 5 s 2 s 2 s 0 s
Operating
conditions- IGN: ON
- B+: below 15.2 VStop
conditions- Time-out
- IGN: OFF
- when engine cranking
If the input power (VB) is 11.5 V or less, the GCU supplies the battery power for arrival time
(T1).
If the input power (VB) is greater than 11.5 V, the GCU supplies the voltage of 11.5 V for arrival
time (T1). 1.
2.
- The time for pre-heating is controlled by the ECU.
The time for pre-heating by coolant temperature can vary slightly depending on e.g. other
vehicle operation elements.