Yanmar 4LHA-HTP Operation Manual page 532

Chapter 6 Cooling Water System
6. Thermostat
6-4 Thermostat inspection
Remove the thermostat cover on top of the fresh water
pump and take out the thermostat. Clean off scale and
rust and inspect, and replace if the characteristics
(performance) have changed, or if the spring is broken,
deformed or corroded.
Part No. of thermostat
Thermostat cover
Gasket
Thermostat
Packing
Fresh water pump body
121850-49810
i-15
6-5 Testing the thermostat
(1) Put the thermostat in a beaker with fresh water, and
heat it on an electric stove. The thermostat is function-
ing normally if it starts to open between 75 ~ 78
opens 8mm (0.3150in.) or more at 90
thermostat if it is not functioning normally.
(2) Normally, the thermostat should be inspected every
500 hours of operation, but, it should be inspected
before this if the cooling temperature rises abnormally
or white smoke is emitted for a long time after engine
starting.
(3) Replace the thermostat every year or 2000 hours of
operation (whichever comes first).
, 4LHA Sen
C, and
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C. Replace the
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