6. Cooling system
121
Thermostat
General Information
The thermosatat maintains water temperature in the
engine consistently and prevents heat loss to improve
heat efficiency of the engine.
When the coolant temperature is below the normal
temperature, the thermostat is closed and the coolant is
bypassed and directly flows into the water pump. When
the coolant temperature reaches the normal temperature
or is higher than the temperature, the thermostat is fully
open and the bypass circuit is closed. So the coolant
flows into the radiator.
DV2213099A
Check of the thermostat
1. Check whether the wax pellet and the spring are
dam
aged or not.
2. Put the water temperature controller into water and
heat the water slowly to check water temperatur
e
cont
roller operation.
3. The water temperature controller is normal in t
he
f
ollowing case: it starts to be open at the water
temperature of 82°C and it is fully open at the water
temperature of 97°C.
DV2213100A_E
4. Check if there is any foreign substance in the water
temperature controller.
Note) Clean the inside of the water temperature controller
with an air gun.
5. Check if there are any foreign substance or damag
e
par
t inside and outside of the hose.
• The wax pellet type thermostat shows slower
r
esponse to the change of cooling water than th
e
b
ellows type thermostat. This happens because
the heat capacity of the wax pellet type water
temperature controller is larger than that of the
bellows type water temperature controller. There-
fore, to prevent rapid increase of engine coolant
temperature, you must first operate the engine at
idle until the engine is fully warmed up. When the
weather is very cold, do not operate the engi
ne
i
n an overloaded condition or at high speed after
starting the engine.
• When draining water from the engine cooler or
injecting water to the engine cooler, work slowly
to let the air in the cooler is fully exhausted.
• When a defect is found in the water temperatur
e
c
ontroller, replace it with a new one.
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