Function Of Cooling System Components - Isuzu 3CH1-NGZG01 Introduction Manual

TNV_OperationManual_T4(under 19kW).book Page 20 Wednesday, June 17, 2015 11:23 AM
PRODUCT OVERVIEW

FUNCTION OF COOLING SYSTEM COMPONENTS

Components
Cooling system
• Engine cooling fan
• Engine coolant pump
• Radiator
• Radiator cap
• Reserve tank
• Thermostat
20
The C series 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
Isuzu factory.
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.
The engine coolant pump circulates the engine coolant through the cylinder
block and cylinder head and returns the engine coolant to the 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.
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 engine coolant to flow from the reserve tank back into the radiator.
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.
A thermostat is placed in the cooling system to prevent 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 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.
Functions