Cooling System; Changing Coolant - Westerbeke BTG 8.5 Operator's Manual

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. 11ris 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 tl_le 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 COOUNG 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
e~temal
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.
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 syst11111 maintenanoe is
oritit:al; a substantiallllllllber of engine failures
t:an
be
trat:ed
bat:k to DDD/ing sysflllll DDIIDSion.
Drain the engine coolant by loosening the drain plug on the
engine block and opening the ma,tifold 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 bot engine coolant.
Wear pmtet:tive 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 sy$tem 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.
TO COOLANT
RECOVERY TANK
COOLANT EXPANSION
PRESSURE CAP
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