Volvo Penta TAD1630G Workshop Manual page 128

Cooling system
Cooling system
The coolant is circulated by an gear-driven pump (4) and is
led in the cylinder block and from there through channels and
openings to the cylinder heads, liner jackets and oil cooler
(6).
On TWD, TID and TD (7), the return flow of fluid from the
cylinder blocks and from the charge air cooler is led via an
outer pipe (3) from the cylinder head to the thermostat hous-
ing (2), which contains two thermostats.
(These illustrations are only examples of the design and function in
the cooling systems for various engines)
1. Radiator
2. Thermostats
3. Distributor pipe for coolant
4. Coolant pump
5. Coolant filter
6. Oil cooler
7. Charge air cooler
Depending of the temperature of the coolant, the fluid is led
either back to the pump, or via an upper radiator hose, into
the radiator.
Around the liners, the cooling jackets of the cylinder block
are divided into an upper and lower plane. The purpose of
this is to concentrate the flow of coolant to the hottest part of
the liner. Through a small gap between the liner and the split
shelf, coolant is led upwards and returns through the cylinder
head.
The coolant space of the cylinder heads is also divided into
two horizontal planes. This means that coolant entering the
head from the block first circulates in the lower section
around the valve seats and injector tips where cooling is vi-
tal. The coolant then flows up into the upper section through
openings around the copper sleeve, circulates around the
valve guides and then leaves via a return pipe which runs
above the cylinder heads.
The left-hand illustration below shows the function of the
thermostat with a cold engine. The picture on the right shows
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