JLG M4069 ANSI Service Manual - Manual (Page 82)

SECTION 4 - HYDRAULICS
4-10 – JLG Lift – 3121122
27. If applicable, install the cartridge type holding valve
and fittings in the rod port block using new o-rings
as applicable. Refer to Table 4-3, Holding Valve
Torque Specifications for proper torque.
IF THE CYLINDER IS TO BE TESTED PRIOR TO INSTALLATION ON
THE MACHINE, EXTREME CARE SHOULD BE USED TO INSURE
THAT THE OUTER END OF THE ROD IS SUPPORTED. USE
EITHER A TRAVELING OVERHEAD HOIST, FORKLIFT, OR OTHER
MEANS TO SUPPORT THE OVERHANGING WEIGHT OF THE
EXTENDING ROD.
4.12 STEER CYLINDER REMOVAL
1. Park the machine on a firm and level surface.
2. Using proper lifting devices raise the machine to
access the steer cylinder form underneath.
NOTE: Be sure and use proper equipment to stabilize the
machine while performing maintenance underneath.
3. Remove both hydraulic lines from the steer cylinder
and allow excess oil in lines to drain into a suitable
container.
4. Remove the nut and bolt from the barrel end of the
cylinder from underneath the machine.
5. Remove the nut and bolt from the rod end of the cyl-
inder from out at the spindle.
6. Remove cylinder from machine.
4.13 OSCILLATION CYLINDER BLEEDING
Bleeding Procedure
1. Run one side wheel onto a ramp or block of wood.
On the other side, the lockout cylinder should be
extended.
2. Block the rear wheels and disconnect the drive
hubs.
3. Open up the bleeder screw on the bottom of the
extended side lockout cylinder. Disconnect coil on
the flow control valve. Have an assistant hold lift up
switch (causing pump to run continually) for approx.
10 seconds or until all the air bubbles are no longer
visible. Then close the bleeder screw while pump is
running.
4. Open bleeder on the top of the retracted lockout cyl-
inder. Let hydraulic oil run for approx. 10 seconds or
until air bubbles are no longer visible. Then close
the bleeder screw.
5. Fully oscillate the axle in the opposite direction and
repeat step three.
Checking Oscillation Cylinders
After bleeding the lockout cylinders, check to see that
they are holding their position when oscillated.
1. Run one wheel onto a ramp or a block of wood,
mark the retracted cylinder with a marker, elevate
platform above high speed cutout.
2. Back the unit off of the ramp, check the retracted
cylinder for drive no more than ½".
3. Repeat this procedure for the other side. If the lock-
out cylinders do not hold, repeat the bleeding proce-
dure or check for the following:
a. Air in lockout system
b. Bad cylinder seals
c. Bad holding valves