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.
ACAUTIDN:
Proper
cooling
system
maintenance
is
critical; a
substantial
number
of
engine
failures
can
be
traced
back
to
cooling
system
corrosion.
COOLANT
ORAIN
M
~;AIEN:SISFOiiiliEO
f'
CAP
RECOVERY
TANK
MANIFOlO
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 accessible.
13
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 petcack
on
the heat exchanger can also
be
used
fo
help drain engine coolant.
AWARNING:
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 petcacks
on
the thermostat housing and heat
exchanger to heip 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 thennostat should also be opened
when refilling
to
allow trapped
air
to escape.
Remove the
cap
on the coolanl 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 tlow into the recovery tank.
After checking for
leaks. stop the engine and allow
it
to cool.
Coolant should draw back into the cooling system as the
engine cools down. Add coolant to the recovery tank
if
needed. Clean up any spilled coolant.
NOTE:
Periodically 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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