Westerbeke BCG4.0KW Operator's Manual page 53

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