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COOLING SYSTEM
DESCRIPTION
Westerbeke marine engines are designed and equipped for
fresh water cooling. Heat produced in the engine by combus-
tion and friction is transferred to fresh water coolant which
circulates throughout the engine. TIris circulating fresh water
coolant cools the engine block, its internal moving parts, and
the engine oil. 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 words, 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 COOLING CIRCUIT
NOTE: Refer
to
the ENGINE COOlANT section for the
recommended 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. When the
engine is started cold, external coolant flow is prevented by
the closed thermostat (although some coolant flow is
bypassed around the thermostat to prevent the exhaust mani-
fold from overheating).
As
the engine warms up, the thermo-
stat gradually opens, allowing full flow of the engine's
coolant to flow unrestricted to the external portion of the
cooling system.
~oolant
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. TIris
tank
should be located at or above the
engine manifold level and should be easily accessible.
NOTE: Periodically check the condition of the manifold pres-
sure 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.
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 petcock on the heat exchanger should also
be used to help drain engine coolant.
A
WARNING:
Beware of the hot engine coolant.
Wear protective gloves.
Refilling the Coolant
After replacing the engine block drain plug, close the heat
exchanger's coolant petcock. Then run the engine at idle and
slowly pour clean, premixed coolant into the manifold.
NOTE: Open the air-bleed petcock on the heat exchanger.
When a steady flow of coolant appears at the petcock, close
the petcock
and
fill the system until the manifold remains full.
Monitor the coolant in the manifold and add as needed. Fill
the manifold to the filler neck and install the manifold pres-
sure cap.
Remove the cap on the coolant recovery
tank
and fill with
coolant mix to halfWay between LOW and MAX and replace
the cap. Run the engine and observe the coolant expansion
flow 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.
COOLANT EXPANSION
COOLANT RETRACTION
Engines
&
Generators
13
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