THERMOSTAT
The thermostat is a heat operated valve that controls
engine temperature by regulating the amount of
heated coolant that is discharged (direct flow) or
recirculated (heat exchanger and keel cooler).
As
the
engine temperature increases, the thermostat opens
and allows coolant to circulate. Prior to
the
thermo-
stat opening, a small amount of coolant circulates
through an internal by-pass. The continuous circu-
lation of the coolant through the by-pass allows the
various parts of the engine to warm up at a uniform
rate and avoids localized hot spots.
When the thermostat is not operating properly, the
engine may run too hot or too cold. Overheating may
damage the thermostat
so
that
the
valvewill not func-
tion properly.
Also,
rust or corrosion may interfere
with its operation.
Two
thermostats are used
on
the
4
cylinder J-series
generator sets with front mount heat exchangers.
One thermostat is used on the
1
and
2
cylinder
J-series (all), and on
4
cylinder J-series generator
sets with side mounted heat exchangers. Figure
27
shows the thermostat locations.
If a faulty thermostat is suspected, remove
it
and test
it
for proper opening and closing.
PART
OPENING
NUMBER TEMP.
OF
309-0054 147'
to
154'
164'
to
68OCI
Testing
A
defective thermostat may cause the engine to run
too hot or too cold and must be replaced if faulty.
Thermostats should be tested for proper opening and
closing. If a sticking or faulty thermostat is sus-
pected, test as follows:
WIDE
OPEN TEMP.
'F/MIN.
STROKE
150'/.360
in.
(66OC19.14
mml
1.
2.
3.
4.
5.
6.
7.
309-0130
I
140'
to
145'
Remove thermostat from the cylinder head.
Heat a pan of water
to
the opening temperature
specified in Table
6.
Check temperature using a
thermometer immersed in water.
165'/.130
in.
With the thermostat suspended
in
water at the
specified opening temperature, check to see that
the thermostat begins to open.
It
should be
possible to slip a
0.003 inch
(0.08
mm) feeler
gauge between the valve and thermostat body.
Continue heating the water until the temperature
specified for full opening is reached. Check to see
that the thermostat is open by the amount speci-
fied in Table
6.
Remove
the
thermostat from the hot water and
allow it to cool
in
the surrounding air. The ther-
mostat should close within a
short
time.
If the thermostat sticks
or
does not operate prop-
erly, replace
i€
with
a
new one.
Always
install a new gasket when replacing the
thermostat.
309-0289
Refer to the appropriate parts catalog for the ther-
mostat part number.
(60'
to
63'C) (74OC13.30
mm)
175"
to
182'
(80'
to
84'C) (95OC12.44
mm)
202'/.096
in.
EXPANSION MDJA
MDJB
MDJE
(FRONT MOUNT
HEAT EXCHANGER)
%,THERMOSTAT
EXPANSION
MDJA
MDJB
MDJE
(FRONT MOUNT
HEAT EXCHANGER)
MDJA, MDJE.
MDJC, MDJE,
MDJF
(SEA WATER COOLING
AND KEEL' COOLER)
MDJC, MDJF
(SIDE MOUNT
HEAT EXCHANGER)
"'
&
COVER
.
,
R
GAS
MDJC
MDJF
(SIDE MOUNT
HEAT EXCHANGER)
%,THERMOSTAT
WATER
v
FIGURE
27.
THERMOSTAT LO$ATIONS
TABLE
6
THERMOSTAT TEST
I
309-0298
I
157°t01640
I
184'1.360in.
I
34
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by any means, is strictly prohibited.
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