JLG 4017RS Service Manual - Manual (Page 133)

8-3 3614RS, 4017RS
Hydraulic System
8.2 SAFETY INFORMATION
Petroleum-based hydraulic fluids are used in this machine.
The temperature of hydraulic fluid increases during the
operation of various hydraulic functions. A heated
petroleum-based hydraulic fluid presents a fire hazard,
especially when an ignition source is present.
Accordingly, periodically inspect all hydraulic system
components, hoses, tubes, lines, fittings, etc. Carefully
examine any deterioration and determine whether any
further use of the component would constitute a hazard. If in
doubt, replace the component.
Whenever you disconnect a hydraulic line, coupler, fitting or
other component, slowly and cautiously loosen the part
involved. A hissing sound or slow seepage of hydraulic fluid
may occur in most cases. After the hissing sound has ceased,
continue removing the part. Any escaping oil should be
directed into an appropriate container. Cap or otherwise
block off the part to prevent further fluid seepage.
Hydraulic system maintenance will, at times, require that the
engine be operated. Always follow safety precautions.
A major cause of hydraulic component failure is
contamination. Keeping the hydraulic fluid as clean as
possible will help avoid downtime and repairs. Sand, grit and
other contaminants can damage the finely machined
surfaces within hydraulic components. If operating in an
exceptionally dirty environment, change filters and inspect
the fluid more often. When servicing the system, cap or plug
hydraulic fittings, hoses and tube assemblies. Plug all
cylinder ports, valves and the hydraulic reservoir, and pump
openings until installation occurs. Protect threads from
contamination and damage.
Some hydraulic functions are actuated by interfacing with
electrical system components (switches, solenoids and
sensors). When the hydraulic system is not functioning
properly, check the electrical aspect of the malfunctioning
circuit also.
Some hydraulic functions are actuated by interfacing with
electrical system components (switches, solenoids and
sensors). When the hydraulic system is not functioning
properly, check the electrical aspect of the malfunctioning
circuit also. Refer to Section 9.5, “Electrical System
Schematics,” in this manual.
8.3 SPECIFICATIONS
Refer to Section 2.4, “Specifications,” for hydraulic system
specifications.
8.4 HYDRAULIC PRESSURE DIAGNOSIS
8.4.1 Pressure Checks and Adjustments
When diagnosing trouble in the hydraulic system, use the
hydraulic testing information in Section 8.5.1, “Hydraulic
Pressures.”
In general, follow the steps below whenever conducting
pressure checks and performing adjustments:
1. Park the machine on a firm, level surface. Engage the
park brake, place the travel select lever in (N) NEUTRAL,
level the boom and turn the engine OFF.
2. At the proper test port, install a pressure gauge capable
of measuring at least 10% more pressure than that
which the circuit being checked operates under.
3. Start the engine. Operate machine functions several
times to allow hydraulic oil to reach operating
temperature. The hydraulic oil temperature should be
between 38-49° C (100-120° F). If a temperature gauge
or thermometer is unavailable, the hydraulic oil reservoir
should be warm to the touch.
4. Refer to Section 8.5.1, “Hydraulic Pressures,” for testing
procedures.
5. Fully depress the accelerator pedal if required. Place and
hold the joystick in the position needed to operate the
particular machine function being checked. Continue
holding the joystick in position until pressure readings
are taken.
6. Check the pressure gauge reading. It should read as
specified in the Pressure Readings column of the charts
found in Section 8.5.1, “Hydraulic Pressures.” If the
reading is not as specified, turn the engine OFF and
check other components in the system. Verify that all
related hydraulic components and electrical switches,
sensors, solenoids, etc. are operating correctly.
7. Adjust the relief valve by turning the adjustment screw.
Turning clockwise will increase the pressure; turning the
screw counterclockwise will decrease the pressure.
8. Start the engine and check the pressure again. Turn the
engine OFF. If there is pressure reading in the gauge,
bleed it off then disconnect or remove the pressure
gauge from the machine.
WARNING
DO NOT service the machine without following all safety
precautions as outlined in Section 1, “Safety Practices,” of
this manual.