TM10-3950-672-24-2
An incorrect or malfunctioning thermostat can cause the
engine to run too hot or too cold.
As described in the coolant discussion, a jiggle pin fitted
to an opening in the thermostat flange is used to vent air
during filling of the coolant system.
After the engine is vented and filled, the jiggle pin acts
as a check valve to block the flow of coolant through the
opening during engine operation.
Note: A missing jiggle pin can cause
the engine to run cold.
With the jiggle pin sealing the opening, most of the flow
to the radiator is controlled by the thermostat in
response to the engine coolant temperature.
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