Coolant Thermostat - Doosan DX140R Shop Manual

Coolant Thermostat

General Information
The thermostat controls the engine coolant temperature. When
the coolant temperature is below the operating range, engine
coolant is bypassed back to the inlet of the water pump. When
the engine coolant temperature reaches the operating range, the
thermostat opens, sealing off the bypass, forcing engine coolant
to flow to the radiator or heat exchanger.
An incorrect or malfunctioning thermostat can cause the engine
to run too hot or too cold.
Never operate the engine without a thermostat. Without a
thermostat, the path of least resistance for the coolant is
through the bypass to the water pump inlet. This can cause
the engine to overheat.
A missing check ball can cause the engine to run cold,
resulting in engine damage.
The thermostat contains two check balls to vent air past the
thermostat when it is closed. This is needed for the cooling
system to fill.
Some off-highway applications use a thermostat with
NOTE:
one check ball. When servicing a thermostat always
be sure to replace with the same part number.
Though an incorrect thermostat will physically fit, it
will lead to improper engine operation.
QSB4.5 Engine
CAUTION!
CAUTION!
Figure 175
Figure 176
Figure 177
SP001671
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