WORKSHOP MANUAL
EDITION
PAGE
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The steering unit is connected to the steering wheel via the steering column. During the steering,
the steering wheel moves a gear that has an orbital movement with respect to the external toothed
gear. Inside the steering unit, the rotor, which acts as a volumetric dispenser, releases a quantity
of oil proportional to the steering angle made by the steering wheel.
The operating conditions for the steering valve to fulfil its function are:
• the motor running at full speed;
• the steering wheel rotated to the right or the left.
The loading pump (1) pushes the oil through the steering valve (3). The flow of oil is indicated by
the arrows in the figure.
When the hydraulic steering valve (3) comes into operation, a pressure drop is generated, down-
stream of the steering valve (5), which amplifies the torque applied to the steering wheel.
The pressure drop depends on the effort required and is limited by the built-in valve (1c).
Hydraulic oil under pressure can be very dangerous if there are leaks
from fittings, pipes or other parts of the system. To avoid personal injury, always wear
protective gloves and goggles when working on the hydraulic system.
Before starting the troubleshooting, it is necessary to check that the following conditions are met:
• by-pass valves of each transmission group in running position;
• oil level in the tank as prescribed;
• absence of air in the hydraulic oil.
1. Rear axle
1a Loading pump (35-45
bar)
1b Main pump
1c Pressure limiter of the
loading pump
1d Oil filter
2. Oil tank
3. Hydraulic steering valve
= Maximum delivery
pressure (50 bar)
= Return (<1 bar)
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