ENGINE
COOLING
CIRCUIT
DESCRIPTION
Westerbeke marine diesel generators are designed and
equipped for fresh water cooling. Heat produced in the
engine by combustion and friction is transferred
to
fresh
water coolant which circulates throughout the engine. This
circulating fresh water coolant cools the engine block and its
internal moving parts. The heat is transferred externally from
the fresh water coolant to raw water by means
of
a heat
exchanger, similar in function to an automotive radiator. Raw
water flows through the tubes
of
the heat exchanger while
fresh water coolant flows around the tubes; engine heat trans-
ferred to the fresh water coolant
is
conducted through the
tube walls to the raw water which is then pumped into the
exhaust system where finally
it
is discharged overboard. In
other
w~rds,
the engine
is
cooled by fresh water coolant, this
coolant
IS cooled by raw water, and the raw water carries the
transferred heat overboard through the exhaust system. The
fresh water coolant and raw water circuits are independent
of
each other. Using only fresh water coolant within the engine
allows the cooling water passages to stay clean and free from
harmful deposits.
Fresh
Water
Circuit
NOTE:
Refer to ENGINE COOLANT section for the recom-
mended antifreeze and water mixture to be used as the fresh
water coolant.
Fresh water coolant
is
pumped through the engine by a circu-
lating pump, absorbing heat from the engine. The coolant
then passes through the thermostat into the manifold, to the
heat exchanger where it
is
cooled and returned to the engine
block via the suction side
of
the circulating pump.
COOLANT
RECOVERY
TANK
TYPICAL
ENGINE
COOLING
CIRCUIT
When the engine is started cold, external coolant flow is pre-
vented by the closed thermostat (although some coolant flow
is
bypassed around the thermostat to prevent the exhaust
manifold from overheating). As the engine warms up, the
thermostat gradually opens, allowing full flow
of
the engine's
coolant to flow unrestricted to the external portion
of
the
cooling system.
Coolant
Recovery
Tank
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 should be located at
or
above the
engine manifold level and should be easily accessible.
,CHANGING
COOLANT
The engine's coolant must be changed according to the
MAINTENANCE SCHEDULE. If the coolant is allowed to
become contaminated,
it
can lead to overheating problems.
A
CAUTION:
Proper
cooling
system
maintenance
is
critical;
a
substantial
number
of
engine
failures
can
be
traced
back
to
cooling
system
corrosion.
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.
NOTE:
The drain
plug
on the heat exchanger can also
be
used
to drain engine coolant.
A
WARNING:
Beware
of
the
hot
engine
coolant.
Wear
protective
gloves.
THERMOSTAT
·HOUSIN.G
COOLANT
Q
Engines
&
Generators
..
13
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