PREVOST X3-45 Multiplex, Руководство по обслуживанию

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Section 05: COOLING SYSTEM
PA1562
3
1. DESCRIPTION
A radiator and thermo-modulated fan are used
to effectively dissipate the heat generated by the
engine. A centrifugal-type water pump is used to
circulate the engine coolant (Fig. 1).
Two full blocking-type thermostats are used in
the water outlet passage to control the flow of
coolant, providing fast engine warm-up and
regulating coolant temperature.
The engine coolant is drawn from the lower
portion of the radiator by the water pump and is
forced through the transmission cooler before
going through the oil cooler and into the cylinder
block.
FIGURE 1: COOLANT FLOW SCHEMATIC
(IMAGE DDC)
From the cylinder block, the coolant passes up
through the cylinder head and, when the engine
is at normal operating temperature, it goes
through the thermostat housing and into the
upper portion of the radiator. The coolant then
passes through a series of tubes where its heat
is dissipated by air streams created by the
revolving fan and the motion of the vehicle.
Upon starting a cold engine or when the coolant
is below normal operating temperature, the
closed thermostats direct coolant flow from the
thermostat housing through the by-pass tube to
the water pump. Coolant is recirculated through
the engine to aid engine warm up.
When the thermostat opening temperature is
reached, coolant flow is divided between the
radiator inlet and the by-pass tube. When the
thermostats are completely open, all of the
coolant flow is to the radiator inlet.
FIGURE 2: COOLING SYSTEM COMPONENTS (DDC S60
ENGINE)
05116
FIGURE 3: COOLANT SURGE TANK
05132
The cooling system is filled through a filler cap
on the surge tank (Fig. 3). A pressure cap on top
of the surge tank is used to maintain pressure
within the system. When system exceeds
normal pressure rating (14 psi - 96.53 kPa), the
cap releases air and if necessary, coolant
through the overflow tube (Fig.
4). Two
thermostats are located in the housing attached
to the right side of the cylinder head (Fig. 2).
Furthermore, a water temperature sensor
mounted on the cylinder head (radiator side) is
also supplied for engine protection purposes
(DDC S60).
The engine cooling system also provides hot
coolant fluid for the vehicle heating system. Refer
to section 22,
"”HEATING AND AIR
CONDITIONING" in this manual for information
relating to heating system water circulation.