M.3
COOLING
SYSTEM
92.4mm STROKE
SERIES
WSM,
01092
[3]
THERMOSTAT
I
C042F048
(1) Seat
(2) Valve
(3)
Pellet
(4)
Spindle
[Bl
C042F049
(5)
Synthetic Rubber
(6)
Leak Hole
(7)
Wax (solid)
(8)
Wax (liquid)
[4] RADIATOR
(not included in the basic engine)
The thermostat maintains the cooling water at
correct temperature. KUBOTA's engine uses a wax
pellet type thermostat. Wax
is
enclosed
in
the pellet.
The wax
is
solid at low temperatures, but turns liquid
at high temperatures, expands and opens the valve.
(A) At low temperatures (lower
than
71°C (1 59.8"F)
).
As the thermostat
is
closed, cooling water
circulates
in
the engine through
the
water return
pipe without running to the radiator. Air
in
the
water jacket escapes to the radiator side through
leak hole
(6)
of
the
thermostat.
(B) At
high
temperatures (higher than 71°C (159.8'F).
When the temperature of cooling water exceeds
71°C
(1
59.8"F), wax
in
the pellet turns
liquid
and
expands. Because the spindle
(4)
is
fixed, the
pellet
(3)
is
lowered, the valve
(2)
is
separated
from
the
seat
(l),
and then cooling water
is
sent
to the radiator.
0076FO
14
[5]
RADIATOR
CAP
C042F050
[AI
101
1
F033
[BI
00
1
1
F034
The radiator core consists of water carrying
tubes
and fins
(3)
at a right angle to the tubes
(2).
Heat
of
hot water
in
the tubes
is
radiated from the tube walls
and
fins.
KUBOTA's engine uses corrugated
fin
type
core
which
has a
light
weight and high heat transfer
rate. Clogging
is
minimized by the louverless
corrugated
fins.
(1) Cooling Air
(2)
Tube
(3)
Fin
(4)
Louverlesr Corrugated Fin
(5)
Louvered Corrugated Fin
The radiator cap
is
for sustaining the internal
pressure
of
the cooling system at the specified level
88 kPa (0.9 kgfkmz,
13
psi) when
the
engine
is
in
operation.
The
cap consists of a pressure valve
(1)
a
vacuum valve
(2),
valve springs, gasket, etc.
Cooling water
is
pressurized by thermal expansion
of steam, and as
its
boiling temperature rises,
generation
of
air bubbles
will
be
suppressed. (Air
bubbles
in
cooling water lowers the cooling effect.)
[A]
When radiator internal pressure
is
high
(81
When radiator internal pressure
is
negative
(1) Pressure Valve
(2)
Vacuum Valve
M-17
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