6. Cooling system
113
Thermostat
General Information
The thermosatat maintains water temperature in the engine
consistently and prevents heat loss to improve heat effi-
ciency of the engine.
When the coolant temperature is below the normal tempera-
ture, 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 radi-
ator.
DV2213099A
Check of the thermostat
1. Check whether the wax pellet and the spring are
damaged or not.
2. Put the water temperature controller into water and heat
the water slowly to check water temperature controller
operation.
3. The water temperature controller is normal in the
following case: it starts to be open at the water tempera-
ture 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 damage part
inside and outside of the hose.
• The wax pellet type thermostat shows slower
response to the change of cooling water than the
bellows type thermostat. This happens because the
heat capacity of the wax pellet type water tempera-
ture controller is larger than that of the bellows type
water temperature controller. Therefore, 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 engine in an overloaded condi-
tion 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 temperature
controller, replace it with a new one.
1. Heat exchanger 3. Coolant pump
2. Bypass valve 4. Coolant pipe
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