JLG 4017 Service Manual - Manual (Page 115)

8.15 4017
Hydraulic System
5. Label or otherwise mark the hydraulic hoses on each
side and bottom of the park brake valve. Disconnect
and cap all hoses, fittings, etc.
6. Remove the two capscrews, and two lockwashers
mounting the park brake valve to the left side of the
seat base.
Note: DO NOT disassemble the park brake valve. The
park brake valve is not serviceable and must be replaced
in its entirety, if defective.
b. Park Brake Valve Installation
1. Install the park brake valve with the two lockwashers
and two capscrews to mount the park brake valve to
the left side of the seat base.
Note: ALWAYS replace seals, o-rings, gaskets, etc.,
with new parts to help ensure proper sealing and
operation. Lubricate seals and o-rings with clean
hydraulic oil.
2. Use new oiled o-rings as required. Uncap and
reattach and secure the three hoses.
3. Check the routing of all hoses for sharp bends or
interference with any rotating members, and install
tie wraps and/or protective conduit as required.
4. Start the engine and run at approximately one-third
to one-half throttle for about one minute, without
moving the machine or operating any hydraulic
functions.
5. Inspect the park brake valve and connections for
leaks, and check the level of the hydraulic fluid in the
reservoir. Shut the engine OFF.
6. Wipe up any hydraulic fluid spillage in, on, near and
around the machine, work area and tools.
8.7.4 Steering Orbitrol Valve
The steering orbitrol valve (2) is located at the base of the
steering wheel shaft, concealed by the lower dash cover.
The valve is not serviceable and must be replaced in its
entirety if defective. For detailed information refer to
Section 4.3.1, “Steering Column and Orbitrol Valve.”
8.7.5 Steer Select Valve
The machine can be used in the front-wheel, four-wheel
or crab steering mode. The steer select valve (3) controls
the direction of hydraulic fluid flow to the steering cylinder
mounted on each axle. The steer select valve is attached
to a mounting plate inside the frame near the left front
corner of the cab.
Verify the correct operation of the steer select valve
solenoids before considering replacement of the valve.
Refer to Section 9.5, “Electrical System Schematics,” and
Section 9.12.1, “Digital Display "Main Screen".” The
housing of the steer select valve is not serviceable and
must be replaced if defective.
a. Steer Select Manifold and Valve Removal
1. Park the machine on a firm, level surface, fully
retract the boom, raise the boom, place the
transmission control lever in (N) NEUTRAL, engage
the park brake and shut the engine OFF.
2. Place an Accident Prevention Tag on both the
ignition key switch and the steering wheel, stating
that the machine should not be operated.
3. Open the engine cover. Allow the system fluids to
cool.
MZ0370
2 WARNING:
DO NOT get under a raised
boom unless the boom is blocked up. Always
block the boom before doing any servicing that
requires the boom to be up. Unexpected lowering
of the boom may cause death or serious injury.
MZ0380
3