Maintenance manual for sunray hfc4da1-2c china-IV diesel engines
64
Section VII Cooling System
z The cooling system is functioned to maintain the engine within an appropriate temperature range under all
working conditions.
z The cooling system can prevent the engine against overheating and prevent the engine from being too cold in
winter.
z After the cold start of the engine, the cooling system can guarantee the rapid temperature rise of the engine to
reach normal working temperature as soon as possible.
z Composition: Water pump, cooling fan, silicone oil fan clutch, thermostat, engine cylinder block, water jacket in
cylinder head, and other accessories.
z The cooling system is of enclosed forced recirculation water cooling type. Its structure is mainly composed of
radiator (water tank), water pump, fan, thermostat, cooling water jacket, and pipeline.
z The cooling recirculation of the heater system and engine oil cooler is always under working state and is not
subject to the restraints of large or small recirculation.
Dual thermostat control: When the water temperature is less than 82ºC, the thermostat is under natural state (namely
the cooling water from the water tank is closed and the cooling water from the cooling module is opened). In such
case, the cooling circuit works in the small recirculation circuit and the cooling water from the cooling module enters
into the engine block and cylinder head for recirculation through the water pump so that the temperatures of the water
and oil in the engine block and the cylinder head will rise. When the water temperature reaches 82ºC, the thermostat
starts to open. When the thermostat is opened, the small valve closes the small recirculation circuit. As the thermostat
is not fully opened, the cooling water from water tank enters into the cylinder block for large recirculation through
water pump. If the water temperature continues to rise to 95ºC, the thermostat valve is fully opened.
Water tank
Radiator
Cylinder head
Cylinder block
Thermostat
Water pump
Heater
Oil cooler
Inlet of
water
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