
FUNCTION
OF
MANIFOLD
PRESSURE
CAP
From Coolant Tank
to Coolant Yank
COOLANT
EXPANSION
Coolant from the engine, when heated during the engine's operation, will expand,
lift
the spring-loaded
manifold pressure cap, and enter the recovery tank via the hose connecting the recovery tank
to
the manifold.
When the engine is shut
down
and cools, a small check valve in the pressure cap is opened
by
the contrac-
tion
of
the engine's coolant, allowing some
of
the coolant in the recovery tank
to
be drawn back into the
engine's cooling system, free
of
air and without loss. Periodically check that the passage
(Al
between the
90· fitting on the manifold and the filler neck in the manHold is clear so coolant can flow in either direction.
Fill the fresh water system as follows:
1.
Remove the pressure cap from the manifold.
2.
Pour a clean, fresh water coolant mixture into the manHold and allow enough time for the coolant
to
fill
the fresh water cooling system and expel
all
air.
3.
Replace the pressure cap on the manifold.
4.
Remove the plastic cap from the coolant recovery tank and fill the tank with coolant halfway between the
ADD mark and the MAX mark. Replace the cap on the manifold.
5.
Start and run the engine long enough for the engine
to
warm up so the thermostat will open, allowing the
coolant to flow through the engine block and to the rest of the fresh water cooling system.
6.
Add coolant
to
the recovery tank, as required,
to
top
off the fresh water cooling system.
Thermostat
Generally, thermostats are of
two
types. One
is
simply a choking device which opens and closes as the
engine's temperature rises and falls. The second type has a bypass mechanism. Usually this is a disc on
the bottom
of
the thermostat which moves downward to close off
an
internal bypass passage within the
head.
Since 1980, each type
of
thermostat has a hole punched through it. The hole is a bypass
to
prevent
the exhaust manifold from overheating during the engine's warm-up. Replacement thermostats must have
this design characteristic.
Westerbeke Generators
50
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