Cooling System - Onan MJA Series Service Manual

COOLING WATER
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FROM SOURCE
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3.1 Cooling System
HI
The cooling system on the MJA, MJB and MJC generating plants is a
liquid coolant, pressure circulating, open type system that uses raw
coolant (city water, sea water ... ).
NOTE: Factory installed heat exchangers for a closed type system are
available as an optional feature and are discussed separately in
Sect 3.1. 4 .
In a raw water cooling system, water enters the pump located on the
front left side of the engine. The pump delivers the water to the bottom
of the cylinder jacket and it flows up the jacket and out an opening in the
cylinder head controlled by the thermostat. For engine warm-up, when
the thermostat is closed, a by-pass from the cylinder block entrance to
the thermostat cover allows water flow. In addition, a notch in the
thermostat allows some water flow through the cylinder jacket and
heads. From the thermostat, water passes through the water cooled
exhaust manifold (except onMJA) and out of the engine cooling system.
CYLINDER
HEAD~
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CYLINDER
B~LOCK ~\,
DRAIN "
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FIG 3.1. A - CROSS SECTION, MJB COOLING SYSTEM