Specifications

Cooling system
chap. 5
5-2
Release 00 2002-09
Atlantic 500
SYSTEM DESCRIPTION
The cooling system is comprised of a centrifugal pump that is coaxial to the countershaft and for this reason, it
makes the same number of revolutions as the engine shaft.
The pump has two intake pipes and one outlet pipe.
The outlet feeds the cylinder and as a result, the head; one intake comes from the head and is controlled at the
pump intake by the thermostat cap.
The main seal of the thermostat operates on the main intake pipe of the pump, which comes from the radiator.
The radiator is supplied by the head outlet; the expansion tank is parallel to the radiator with pipes on two levels:
delivery on top (in air) and fluid return at the bottom (in the fluid).
The system is of the two-way type.
The first path is formed by circulation inside the engine and involves the pump, cylinder and head; this type of
circulation is completely enabled when the thermostat is fully closed.
The second path is enabled when the thermostat is fully open and is the main circulation, involving pump, cylinder,
head, radiator, and expansion tank. For medium thermostat openings, both circuits are partially enabled and
therefore, the two paths overlap.
This type of circuit is defined as having an intake thermostat. The thermostat is crossed by an inverse flow; that is,
with cold water, which tends to lower the temperature of the wax cell.
This system allows optimization of the heating stages of the engine.
The expansion tank, which is parallel to the radiator and inserted into the main circuit, guarantees autobleeding
during operation.
For the system filling stages, there is a bleeder at the head outlet (see filling regulations).
The electric cooling fan is controlled by the fuel injection system and the relevant temperature is measured on the
engine head.
COOLANT
For information about the coolant, see (COOLANT), (CHECKING AND TOPPING UP COOLANT) and (REPLAC-
ING COOLANT) in the relevant ENGINE WORKSHOP MANUALS n°1063 , n°1064 , n°1065 , n°1066 ,
n°1067 and n°1068 .
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10
Key
1) Radiator/pump pipe
2) Thermostatic valve
3) Pump/head cylinder hose
4) Head/pump hose
5) Radiator
6) Head/radiator hose
7) Expansion tank
8) Expansion tank/radiator
hose
9) Electric cooling fan
10) Water pump unit