Volvo Penta TAMD74A, Operator'S Manual

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Maintenance: Freshwater system
Freshwater system
The freshwater system is the internal engine cooling system. It is a closed system and must always be filled with
a coolant that protects it against internal corrosion and freezing when the climate demands.
The circulation pump ensure good circulation in the system. The thermostat will start to open at a certain temper-
ature and will be fully open when the engine has attained normal operating temperature. When the thermostat
opens, the warm coolant passes through the heat exchanger where it is cooled by the water in the engine’s sea-
water system.
In its standard version, the engine is fitted with an internal freshwater system. Volvo Penta also supply engines
with the cooling system prepared for external cooling, e.g. keel cooling.
Coolant. General
The freshwater system must always be filled with a
coolant that protects it against internal corrosion and
freezing when the climate demands.
Anti-corrosive additives become less efficient with
age and the coolant must therefore be changed.
IMPORTANT ! Never use only water as a cool-
ant and change the coolant in accordance with
the recommendations in the maintenance
schedule.
Water quality
To avoid clogging the system, the coolant must be
mixed with pure water in accordance with ASTM
D4985. If there are doubts about the purity of the wa-
ter, use distilled water or ready-mixed coolant in-
stead.
ASTM D4985:
Total solid particles ....................................... < 340 ppm
Total hardness ................................................ < 9.5° dH
Chloride ........................................................... < 40 ppm
Sulphate .......................................................... < 100 ppm
pH-value .......................................................... 5.5–9
Silicon ............................................................. < 20 mg SiO
2
/l
Iron ................................................................... < 0.10 ppm
Manganese ...................................................... < 0.05 ppm
Conductivity ................................................... < 500 µS/cm
Organic content, COD
Mn
................................ < 15 mg KMnO
4
/l