MAINTENANCE MANUAL OF ENGINE
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5. Cooling system
Function:
The engine can be kept within an appropriate
temperature range in all conditions.
Cooling method:
The engine is cooled by means of closed-type
positive water circulating, namely that the pressure
of the coolant can be built up by the water pump to
compel the coolant circulation in the engine.
Composition:
It is composed of water pump, radiator, cooling
fan, thermostat, water make-up barrier, engine body,
cylinder liner, cylinder head and other attachments
and etc.
1. Cooling water line:
During operation of the diesel engine, the
crankshaft pulley is operated through driving the
water pump by the belt, so as to pressurize the
cooling water into the water chamber of the engine
body and cool down the cylinder liner, block and
head, and then enter the thermostat. When the outlet
water temperature is lower than 70℃, the thermo-
stat is closed, and the cooling water flows back to
the inlet water chamber via the bottom of the cylin-
der head and corresponding small water pore on the
engine body, and then enter the water pump and
realize small circulation in the engine. When the
outlet water temperature is higher than 70℃-80℃,
the thermostat is fully open, and at this moment, the
cooling water flows into the upper water chamber
of the water tank via the thermostat, and to the low-
er water chamber along the flattened brass pipe. In
this process, the cooling water is cooled by the air
sucked or exhausted by the fan, realizing the big
circulation. According to different applications, the
fan can adopt induced draft or exhaust type.
2. Water pump
The diesel engine adopts centrifugal water
pump. When the water seal is worn and much water
is dropped from the drain hole at lower part of the
water pump body, it is required to change the water
seal, and blockage of the drain hole is not allowed,
otherwise, the water will enter the bearing, making
the bearing worn. If the water leakage is serious, an
abnormal sound is produced during operation of the
bearing, and it is required to change the bearing.
The lubricant nipple of the water pump should
be injected with grease on a regular basis. Usually,
the grease should be replenished every about 200
operating hours for the diesel engine. The lubricat-
ing grease is #4 calcium base lubricating grease.
The lubricating grease level should not be too high,
but about 1/3～1/2 of the bearing chamber. Exces-
sive grease will get the bearing overheated.
3. Thermostat:
The thermostat is a bellows single-valve type,
which is installed in the thermostat housing at the
water outlet at the front end of the cylinder head. It
contains a temperature sensitive fluid to automati-
cally control opening and closing of the valve. Its
model is 155B.
When the temperature of the cooling water for
the diesel engine does not reach 70℃, the thermo-
stat valve remains closed, and the cooling water
undergoes the small circulation in the engine; when
the temperature of the cooling water for the diesel
engine exceeds 70℃, the thermostat valve is open,
the cooling water circulates in the big circuit; and
when the water temperature exceeds 85℃ , the
thermostat valve is fully open.
Attention: If the water temperature is failed to
reach 70℃ and there is water flowing from the
water pipe after the diesel engine is cold-started, or
when the water temperature of the diesel engine
exceeds 70℃, no water flows out from the water
outlet pipe. This indicates that the thermostat has
been malfunctioned, and should be removed for
inspection.
Do not remove the thermostat at will because
excessively low cooling water temperature is un-
beneficial to normal startup and operation of the
diesel engine.
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