Onan MDJE Service Manual

SIPHON BREAK
A siphon break is used with all marine installations
where the exhaust water injection elbow is
BELOW
the load water line. The siphon break (see Figure 14)
is a vacuum operated vent valve that opens the
exhaust water discharge line to the atmosphere when
the engine shuts down. The open valve prevents
flotation water from being siphoned into the exhaust
manifold. The siphon break is mounted no less than
12 inches (305 mm) above the water line. If space is
limited it may be remotely mounted but must be
within
5 feet more than (1.5 m) of the exhaust water
injection elbow. In all installations the siphon break
must be mounted vertically with the threaded end
pointing down.
Be sure fhe slofted opening in fhe
vacuum relief valve
is open to af-
mospheric pressure. The siphon break will
nof func-
fion if the relief valve slof is closed in any way.
HANGER STRAPS
RUBBER HOSE
WATER OUTLET
XHAUST WATER
JECTION ELBOW
- EXHAUST OUTLET
FIGURE 14. SIPHON BREAK
HEAT EXCHANGERS
Several types of heat exchangersare currently in use
with marinecooling systems.Thefront mount typeof
heat exchanger shown in Figure
15 is used with the
MDJA and MDJB and was used with earlier models of
the MDJE, and MDJF.
It is mountedat the front of the
engine perpendicular to the engine center line. The
end caps are removable for cleaning and a separate
expansion tank
is required. The sea water side of
these heat exchangers is protected from corrosion
with either one
or two zinc pencils (mounted on pipe
plugs) that are placed in one end of the heat
exchanger.
FIGURE 15.
FRONT MOUNT HEAT EXCHANGER
The side mount type of heat exchanger shown in
Figure
16 is used with later models of the MDJC,
MDJE, and MDJF. It is mounted on the side of the
engine
just above the exhaust manifold.The end caps
are removable
for cleaning and the expansion tank is
incorporated with theoutside shell. On some models,
the sea water side of the heat exchanger is protected
from corrosion with azinc pencil located close to the
sea water inlet. Other models may not have zinc
pencils.
AIR BLEEDER VALVE
HEAT EXCHAN
CENTRIFUGAL EXHAUST AND
PUMP RAW WATER
DISCHARGE
FIGURE 16.
SIDE MOUNT HEAT EXCHANGER
Sea Water Side
Remove and inspect thezinc pencils that are used for
corrosion protection every two months. Replace if
the pencils are deteriorated to less than one half their
original size.
22
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Onan MDJE Specifications

General

Brand	Onan
Model	MDJE
Category	Engine
Language	English