GENERAL SERVICE INFORMATION
4-10
3TNV88F Service Manual
Function of Cooling System Components
FUNCTION OF COOLING SYSTEM COMPONENTS
Components
Functions
Cooling system
The TNV engine is liquid-cooled by means of a cooling system. The cooling
system consists of a radiator, radiator cap, engine cooling fan, engine
coolant pump, thermostat, and reserve tank.
Note that all cooling system components are required for proper
engine operation. Since some of the components are application
specific, they must be carefully selected by an application engineer.
The application specific items are not part of the basic engine package
as shipped from the YANMAR factory.
• Engine cooling fan
The engine cooling fan is driven by a V-belt which is powered by the
crankshaft V-pulley. The purpose of the engine cooling fan is to circulate air
through the radiator.
• Engine coolant pump
The engine coolant pump circulates the engine coolant through the cylinder
block and the cylinder head and returns the engine coolant to the radiator.
• Radiator
The radiator acts as a heat exchanger. As the engine coolant circulates
through the cylinder block it absorbs heat. The heat in the engine coolant is
dissipated in the radiator. As the engine cooling fan circulates air through
the radiator, the heat is transferred to the air.
• Radiator cap
The radiator cap controls the cooling system pressure. The cooling system
is pressurized to raise the boiling point of the engine coolant. As the engine
coolant temperature rises, the system pressure and the coolant volume
increases. When the pressure reaches a preset value, the release valve in
the radiator cap opens and the excess engine coolant flows into the reserve
tank. As the engine coolant temperature is reduced, the system pressure
and volume is reduced and the vacuum valve in the radiator cap opens
allowing the engine coolant to flow from the reserve tank back into the
radiator.
• Reserve tank
The reserve tank contains the overflow of engine coolant from the radiator.
If you need to add engine coolant to the system, add it to the reserve tank;
not the radiator.
• Thermostat
A thermostat is placed in the cooling system to prevent the engine coolant
from circulating into the radiator until the engine coolant temperature
reaches a preset temperature. When the engine is cold, no engine coolant
flows through the radiator. Once the engine reaches its operating
temperature, the thermostat opens and allows the engine coolant to flow
through the radiator. By letting the engine warm up as quickly as possible,
the thermostat reduces engine wear, deposits and emissions.
3TNV88F_SVM_A4.book 10 ページ 2012年7月26日 木曜日 午後6時4分