WORKSHOP MANUAL
PARK
Chapter
EDITION
2020
PAGE
91 /
124
8.2.2 By-pass valves
The by-pass valve has the purpose of making it possible to push the machine by hand, without
strong resistance due to the resistance of the oil in the circuits in the absence of pressure.
When a by-pass valve is open, it allows the oil to flow into the engine casing and therefore the
pressure drop on the engine is neutralized.
▶▶
Park 4WD machines:
Both transmission units are equipped with a by-pass
valve, each of which is connected to the respective
operating lever.
The front by-pass valve is equipped with a mechanical
interlock that always restores the valve, if previously
opened, to attempts to move forward.
Driving the machine forward, with the rear by-pass
valve (1) closed and the front by-pass valve (2) open,
causes a powerful flow of oil into the front transmis-
sion casing.
Because the drain line is not sized for this flow and the
main flow line is closed, a dangerous pressure build-
up occurs in the front transmission casing. This pres-
sure increase forces the oil to seek a vent from the
seals and can cause damage.
NOTE
The activation of the parking brake automati-
cally causes the closure of the by-pass valve of the
front transmission.
8.2.3 Hydraulic steering valve (Booster)
● Operation description
The hydraulic steering valve is a device designed to facili-
tate steering by making the steering wheel lighter. Thanks
to this device, the driver has to apply less force to be able
to operate the steering components.
The system uses a high pressure pump driven directly by
the engine, through a belt, to circulate the oil within an hy-
draulic circuit derived from the rear hydraulic transmission.
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