Chapter 5 System Description; Coolant - APRILIA Atlantic 500 Workshop Manual

Cooling System
SYSTEM DESCRIPTION
The cooling system is constructed with a centrifugal pump coaxial to the countershaft and as such completes a
number of revolutions identical to that of the driving shaft.
The pump has two ducts, one for entry and one for exit.
The exit duct supplies the cylinder and consequently the cylinder head; the entry duct leads from the cylinder head
and its entrance to the pump is controlled by the thermostat plate.
The main stabilizer of the thermostat acts instead on the main pump entry duct leading from the radiator.
The radiator is fed from the cylinder head exit; the expansion tank is inserted parallel to the radiator with the ducts
on two levels: the delivery high up (in the air) and the fluid return low down (in the fluid).
The system thus composed is 2-way.
The first way is the internal engine circulation and involves the pump, cylinder and cylinder head; this circulation is
fully active when the thermostat is fully closed.
The second way is active with the thermostat fully open and is the main circulation which involves the pump,
cylinder, cylinder head, radiator and expansion tank; for medium openings of the thermostat, however, the two
circuits are both partially inserted, therefore the two ways are superimposed.
This kind of circuit is defined as the type with inlet thermostat. The thermostat is crossed by an inverted flow, that is
with cold water which tends to lower the temperature of the wax cell.
This system allows optimization of the engine heating phases.
The expansion tank, parallel to the radiator and inserted on the main circuit, guarantees autodraining when work-
ing.
For the filling stages of the system there is a drain exiting from the cylinder head (see filling rules).
The electrical fan is controlled by the fuel injection system with temperature measured on the cylinder head of the
engine.

COOLANT

For information concerning the coolant see (COOLANT); (CHECKING AND TOPPING UP OF THE COOLANT) and
(REPLACING COOLANT) in the related WORKSHOP MANUALS n°1063
n°1067 and n°1068
1
8
7
5
5-2
.
3
9
Release 00
, n°1064
10
2
6
2002-09
Atlantic 500
, n°1065 , n°1066
Key
1) Radiator/pump pipe
2) Thermostat valve
3) Pump/head cylinder pipe
4) Cylinder head/pump pipe
5) Radiator
6) Cylinder head/radiator pipe
7) Expansion tank
8) Expansion tank/radiator
pipe
4
9) Electrical fan
10) Water pump casing
chap. 5
,