Technical data

19
Group 26 Cooling system
Design and function
General
The engines are water cooled and have a sealed
cooling system. The system is divided into two
circuits.
In the inner circuit (fresh water system), the coolant is
pumped round by a centrifugal coolant pump
(circulation pump).
On the TAMD63, the engine is driven by a belt from
the vibration damper. On the other engines, the pump
is gear driven from the timing gear train.
From the coolant pump, the coolant is pumped out
into a gallery in the cylinder block and is then taken
round the cylinder liners and further up through the
cylinder block.
The coolant then passes from each cylinder block and
from the turbocharger turbine housing back to the
thermostat housing where a thermostat regulates the
coolant temperature. The coolant from the engine oil
cooler is also taken up to the thermostat housing.
As long as the coolant is cold, the thermostat closes
off the flow to the heat exchanger. The coolant then
passes through a by-pass duct beneath the
thermostat, directly back to the inlet side of the pump.
When the coolant temperature has risen to a
previously chosen value, the thermostat opens and
allows coolant to flow to the heat exchanger, at the
same time as the by-pass duct is closed.
In the heat exchanger, the heat from the coolant is
transferred to the sea water before the coolant is
drawn back into the coolant pump again.
Large quantities of heat are also transported away by
the lubricating oil, which transports heat to the fresh
water system via the oil cooler.
The lubricating oil is also used to transport heat from
the pistons in the engine. Please refer to the
Workshop manual “Group 22 lubrication system”, page
13.
The cooling system can operate at a certain excess
pressure. The risk of boiling is thus reduced if the
temperature rises. If the pressure is higher than
normal, a pressure relief valve in the filler cap opens.
Sea water flow is obtained from a gear-driven impeller
pump mounted on the front of the engine.
The sea water passes through the engine heat
exchanger*, aftercooler and reverse gear oil cooler.
There is a zinc anode in the reverse gear oil cooler to
counteract corrosion.
The TAMD63 also has one zinc anode in the heat
exchanger and another one in the aftercooler. It is
important that the condition of the anode(s) is
checked in accordance with the maintenance
schedule, to avoid corrosion damage.
The engine can have a separate expansion tank as an
accessory.
* Note: On the TAMD63, the sea water passes through the after-
cooler before it goes to the heat exchanger and the reverse gear
oil cooler.