Description of engine cooling system

DESCRIPTION OF ENGINE COOLING SYSTEM

1. Water pump
2. Thermostatic cup
3. Cooling fan
4. Radiator
5. Climate control heater
6. Header tank
7. Throttle body
8. Coolant fluid temperature gauge transmitter and maximum temperature warning light contact
9. Coolant fluid temperature sensor
10. Longitudinal manifold
11. Coolant fluid - engine oil heat exchanger

The cooling system is of the sealed type with forced circulation by centrifugal pump (1) located on the cylinder head and controlled by the timing gear belt. A thermostatic valve (2), on the rear of the cylinder head, keeps the engine at optimum temperatures; it opens when the coolant fluid reaches a temperature of 83 °C.

In addition to the flow of dynamic air the radiator (4) cools the engine fluid also through a two-speed fan (3) controlled directly by the MOTRONIC control unit, depending on the signal received from the engine coolant temperature sensor (NTC).

(For further details on how the fan works see ELECTRIC- ELECTRONIC DIAGNOSIS - Sect. 26 for versions with air conditioner and Sect. 27 for versions with heater).

The header tank (7) supplies the circuit if the level falls and acts as a lung absorbing the changes in volume of the fluid as the temperature changes; it also vents air from the circuit.

The circuit is fitted with a coolant fluid temperature transmitter for the gauge and a maximum temperature thermal contact (9) for the warning light.