Yanmar 1GM User Manual page 185

COOLING SYSTEM 179
CLOSED COOLING SYSTEM DIAGRAM
Pressure fill cap
Remote tank
~;;;;;;;;;~~~~5~S~::----[:
Heat exchanger
By-pass
Thermostat
Cylinder block
Cylinder head
Freshwater pump
Seawater line
Mixing
elbow
Seacock
Freshwater line
~
Seawater
10. Ifno signs ofleakage can be found in Step 8 or Step 9,
yet the coolant level continues to require frequent topping
off, there is probably an internal leak. This could be
caused by a blown head gasket, loose cylinder head, or a
cracked or porous head or block.
If extremely dirty or corroded, flush out the remaining
deposits with a pressure flushing device. Refer to the
cooling system flow diagram (Figure 35) and follow the
manufacturer's instructions regarding the connection of
the pressure flushing device and procedure to be fol-
lowed.
Cleaning
Flush and clean the freshwater section every other sea-
son or periodically as needed. Use any high-quality auto-
motive cooling system cleaning solution to remove scale,
rust, mineral deposits or other contamination. Use the
cleaning solution according to the manufacturer's direc-
tions.
Cleaning the Seawater Section of the Heat
Exchanger
Contaminants and minerals collect inside the copper
tubes in the seawater section of the heat exchanger during
engine operation. Such foreign material reduces the abil-
ity of the heat exchanger to operate efficiently and, if not
removed periodically, will eventually lead to engine over-