PRESSURECAP
The
pressure
cap
increases
the boiling point
of
the
coolant
by
allowing
pressure
to
build
up in
the
cool-
ing system. The increase in boiling point reduces the
chances for coolant loss due to boil over.
A
15
psi
(103.5
kPa) pressurecap
will
raisethe boiling pointof
water to
250°F
(122OC) and the boiling point of a
50/50
mixture
of
water and antifreeze to 265°F
(132OC).
Inspect the pressure cap periodically for freedom of
operation and verify that the spring applies a fairly
stiff tension and is not easily compressed. Peel the
pressure cap gasket back and check for wear and
cracking. Excessive dripping from the overflow tube
may indicate a faulty cap. Replace the cap if
it
mal-
functions or is worn.
PART RATED
NUMBER PRESSURE PSI
130-0589 14
130-0661
7
130-0824
15
130-0553 4
(97 kPa)
(48 kPa)
1
(98 kPa)
(28 kPa)
JSERlES
WITH
SEA
WATER
COOLING
OR
KEEL
COOLER
ACCEPTABLE
LIMITS
PSI
(83-98 kPa)
1
2-1
5
-
-
-
-
3.5-4.5
(24-31 kPa)
Contact with hot coolant might
result in serious
bums.
Do
not bleed
hot, pressurized coolant from a closed cooling
system.
PART
NUMBER
309-0259
309-0179
309-0178
309-0002
309-0151
309-0156
309-0192
309-0252
Pressure caps should be inspected regularly for
gasketwear and spring action.
A
pressure tester may
be used if available to verify that the cap can hold its
rated pressure value. The pressure ratings for
the
various caps are shown in Table
4.
Refer to the appropriate Parts Catalog for the pres-
sure cap part number.
TEMPERATURE
OF
OPEN
CLOSE
230'
f7"
(110°C) 190' f9'
(88°C)
190' (88OC)
215"
f5"
(102OC)
180"
(83°C) 205"
25"
(97°C)
160"
f5"
(71'C)
200" -1-7' (93°C)
200'
25'
(93°C)
160" 57' (71°C)
250'
f5'
(121°C)
230' -1-7" (110°C)
290" 18" (143°C)
250"
f12" (121°C)
200'
f5"
(93'C)
160"
f7' (71°C)
HIGH
TEMPERATURE CUT-OUT
SWITCH
A
high temperature cut-off switch shuts down the
engine if the coolant in the water jacket reachesa
dangerously high temperature. This normally closed
switch is
a
safety device designed
to
protect the
engine from damage caused
by
overheating (see
Figure
26).
UT-OFF
SWITCH
THERMOSTAT
HOUSING
FIGURE
26.
HWTKO
SWITCH
When
engine
temperature rises beyond a specific
point the switch opens breaking
B+,
allowing fuel
solenoid to close on diesel engines. When coolant
temperature lowers to a safe operating range the
switch closes, permitting engine restarting.
A
second high temperature cut-off switch is some-
times used with generator sets that have a water
injected exhaust system. The second switch
is
mounted on the exhaust elbow (see Figure
13).
If the
exhaust system overheats, theswitch shutsdown the
generator set before the exhaust system components
are damaged. The two switches are wired together in
series
so
that opening either switch will shut down
the engine.
Stopping of the engine due to action of the high
temperature cut-off switch is not
a
normal condition.
Examine the cooling system to determine the cause
of the overheating and repair as required. The open-
ing and closing temperatures for each switch are
shown in Table
5.
Refer to the appropriate
Parts
Catalog for the part number
of
the high temperature
cut-out switch used
in
the engine being serviced.
TABLE
5
HIGH
TEMP
CUT-OUT SWITCH
33
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by any means, is strictly prohibited.
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