ENGINE
COOLING
CIRCUIT
DESCRIPTION
The engine
is
fresh
water cooled (engine coolant)
by
an
engine-mounted heat exchanger.
Raw
water
is
pumped
through
the
heat.
exchanger
by
a
gear-driven,
positive dis-
placement impeller pump. After
the
raw water cools the
engine coolant in the heat exchanger, it
mixes with the
engine's
eXhaust
gases,
cools the exhaust gases, and dis-
charges
overboard.
The
engine's coolant
is
circulated
by
a belt-driven centrifu-
gal-type
metal
impeller pump mounted
on
the front
of
the
engine.
The engine's coolant temperature
is
thermostatically
controlled.
The engine's coolant
must
be
changed according
to
the
main-
tenance
schedule·
in this
manual.
If
the coolant
is
allowed
to
become contaminated,
it
can
lead
to
overheating problems.
AcAUTION:·
Proper
cooling
system
maintenance
is
crif!cal; a
substantial-number
of
engine
failures
can
be
traced
back
to
cooling
system
corrosion.
A coolant
recovery
tank allows
for
engine coolant expansion
and
contraction during engine operation, without
any
signifi-
cant loss of coolant
and
without introducing air into the
cool-
ing
system.
This
tank
is
best located at
or
above the engine
manifold
level,
and should
be
easily
accessibie.
. .
M-508
COOLANT
DRAIN
JUST
ABOVE
THE
RIGHT
FRONT
ENGINE
MOUNT
~
MANIFOLD
MANIFOLD
PRESSURE
CAP
Drain the engine coolant
by
loosening the drain plug
on
the
engine block and opening
the
manifold pressure
cap.
Flush
the
system with fresh
water,
then start the refill process. See
the
Parts Identification photos in this manual for locations.
·
NOTE:
The
petcock
on
the
heat exchanger
can
also
be
used
to
help
drain
engine
coolant.
A
wARNING:
Beware
of
the
hot
engine
coolant.
Wear
protective
gloves.
To
Refill
With
Coolant
With
the engine running
in
idle, slowly pour clean premixed
coolant into the manifold.
NOTE:
Open
the
petcocks
on
the
thennostat
housing
and heat
exchanger
to
help
remove
air from
the
system.
When
a
steady
flow
of
coolant
appears
at
the
drain
plug
opening,
close
the
water
drain
plug
and
continue
to
fill
the
system until
the
manifold
remains
full.
Close
'the
petcock on
the
heat
exchanger
when
antifreeze
flows from
it.
·
Monitor the coolant
in
the manifold and add
as
needed. Fill
the
manifold
to
the filler neck and install the pressure
cap.The petcock
on
the
thermostat should
also
be
opened
when refilling
to
allow
trapped air
to
escape.
Remove the cap on
the
coolant recovery tank,
fill
with
coolant
mix
to
halfway between
LOW
and
MAX,
and
replace the cap. Run
the
engine, close
all
petcocks
and
observe the coolant expansion flow into the recovery
tank.
After checking
for
leaks,
stop
the engine and
allow
it
to
cool.
Coolant
shouii draw back into the cooling system
as
the
engine cools
do·vn.
Add
coolant
to
the recovery tank if
needed. Clean
t1P
.''lilY
spilled coolant.
PRESSURE
CAP
NOTE:
Periodicq.lly
check
the
condition
of
the
pressure
cap.
Ensure
that
the
upper
and
lower rubber seals
are
in
good
condition and check
that
the
vacuum
valve
opens
and
closes
tightly.
Carry
a
spare
cap.
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