Volvo Penta D4 Operator's Manual page 76

Maintenance
74
Freshwater System
The freshwater system is the engine's internal cooling
system that ensures that the engine operates at the
correct temperature. It is a closed system that must
always be filled with a mixture of concentrated coolant
and water in order to protect the engine against internal
corrosion, cavitation and frost bursting.
We recommend "Volvo Penta Coolant, Ready Mixed",
or "Volvo Penta Coolant" (concentrated) mixed with
pure water according to specifications. Refer to the
table Water Quality page 115. Only coolant of this
grade is suitable for, and approved by, Volvo Penta.
The use of anti-corrosion agents alone is not permitted
in Volvo Penta engines. Never use water alone as the
coolant.
IMPORTANT!
Coolant of a suitable chemical composition must be
used all year round. This applies even when there is
no risk for frost damage, so that the engine always has
complete corrosion protection. Future warranty claims
related to engine and accessories may be refused if an
unsuitable coolant has been used, or if the instructions
for coolant mixture have not been followed.
The corrosion protection additives become less effec-
tive over time, which means that the coolant must be
changed at regular intervals; refer to the Maintenance
Schedule page 58. The cooling system must be
flushed whenever the coolant is changed, refer to the
Freshwater system, Flushing section.
"Volvo Penta Coolant" is a concentrated coolant that
must be mixed with water. It has been prepared to work
best with Volvo Penta engines and offers excellent
protection against corrosion, cavitation damage and
frost bursting.
"Volvo Penta Coolant, Ready Mixed" is a ready-
mixed coolant, 40% "Volvo Penta Coolant" and 60%
water. This mixture protects the engine from corrosion
damage, cavitation damage and frost bursting down to
–28°C (–18°F).
7748934 04-2008