Water Pump
The centrifugal type water pump is used in the
cooling system. The pump impeller is supported
by a totally sealed bearing. The water pump can
not be disassembled.
Fig. 6-4
Thermostat
A wax pellet type thermostat is used in the
coolant outlet passage to control the flow of
engine coolant, to provide fast engine warm up
and to regulate coolant temperatures.
A wax pellet element is hermetically contained
in a metal case, and expands when heated and
contracts when cooled.
When the pellet is heated and expands, the metal
case pushes down the valve to open it.
As the pellet is cooled, the contraction allows a
spring to close the valve.
Thus, the valve remains closed while the coolant
is cold, preventing circulation of coolant through
the radiator.
In the top portion of the thermostat, an air
bleed valve is provided; this valve is for venting
out the gas or air, if any, that is accumulated in
the circuit.
There are two types of thermostat, A and B, as
given below. Either one is used depending on
vehicle specifications. The temperature at which
the valve begins to open is stamped on each
thermostat. Be sure to note this stamped tempe-
rature for replacement.
I
Thermostat functional
spec.
f
1.5’C (2.7’F)
I
I
IThermostat
“A” (Thermostat “B”
1
Temp.
at
which
valve begins to
82°C
(179’F)
open
BB’C
(190°F)
Temp. at which
valve become
fully open
95%
(203’F)
1OO’C
(212’F)
Valve lift
More than
More than
8
mm at
95’C
8
mm at
1OO’C
Fig. 6-5 Thermostat
1.
Air bleed valve
At this point, coolant is allowed to circulate
only throughout the engine to warm it quickly
and evenly.
As the engine warms, the pellet expands and the
thermostat valve opens, permitting coolant to
flow through the radiator.
6-4
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