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When draining the engine, open the pressure cap first to relieve the
vacuum created by draining.
10.
FILLING THE FRESH WATER SYSTEM
It is very important to completely fill the fresh water system before
starting
the
engine.
It
is
normal
for
air
to
become
trapped
in
var ious passages so all high points must be opened to atmosphere to
bleed entrapped air.
When an engine is started after filling wi th
coolant,
the
system may look deceptively full until the thermostat
opens.
At this time when water flows through the external cooling
circuit for the first time, pockets of air can be exposed and rise to
the fill point.
Be sure to add coolant at this time.
After a number of seasons' use of the engine, water scale and rust may
occur
in
the
block
water
jacket
and
exchanger,
resulting
in
con-
siderable reduction of cooling efficiency.
Therefore, it is necessary
to flush the cooling system once every two or three years.
CAUTION:
Adhere to
the manufacturer's
instructions when
using
the additive.
Do not mix different brand products.
Be sure to put the proper amount of antifreeze in water and agi-
tate well before adding it to the cooling system.
Du not use a
concentrated antifreeze solution.
11. THERMOSTAT
Generally,
thermostats are of
two
types.
One
is simply a choking
device which opens
and closes as
the engine
temperature rises
and
falls.
The second type has a by-pass mechanism.
Usually this is a
disc on the bottom of the thermostat which moves downward to close off
an
internal by-pass passage wi thin
the head.
Both types of ther-
mostats, from 1980 onwards, have a hole punched through them to serve
as
a
by-pass
while
the
engine
is
warming
up.
This
prevents
overheating
in
the
exhaust
manifold
during
engine
warm-up.
Replacement thermostats must be equal in this design characteristic.
When replacing a thermostat, be sure that it is rotated so as to not
strike
the
thermostat
housing,
projections
inside
the
head,
tem-
perature senders or temperature switches which may be installed close
to the thermostat.
Also insure the by-pass hole is not blocked by any
part of the housing.
A thermostat can be checked for proper operation by placing it in a
pan of cold water and then raising the temperature of the water to a
boil.
The thermostat should open noticeably (with travel on the order
of 1/4
n
-
1/2
n )
and be fully opened when the water is boiling.
12. WATER TEMPERATURE SWITCH
The water temperature switch is located in the thermostat housing at
the front of the cylinder head.
This switch will close on a pro-
pulsion at 205·
F
to activate an alarm buzzer
and on a generator
engine it will open to de-energize the fuel run solenoid to shut the
engine off.
I I I
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