Lull 944E-42 Service Manual - Manual (Page 477)

8.225 Model 644E-42/944E-42 Rev. 6/04
Hydraulic System
IMPORTANT: When sliding the rod (5) and piston
assembly in the tube, prevent the threaded end of the
tube from damaging the piston (7). Keep the rod
centered within the tube to help prevent binding. Protect
the finish on the rod at all times. Damage to the surface
of the rod can cause seal failure.
13. Carefully insert the rod (5), with all attachments,
straight into the tube (2).
14. Using a pin spanner wrench, thread the head
gland (6) into the tube (2). Torque the head gland to
300-400 lb-ft (407-542 Nm).
15. Lubricate the counterbalance valve (3) and the pilot-
operated check valve (4) with clean, filtered
hydraulic oil. Using all new seals, thread the
counterbalance valve and the pilot-operated check
valve into the trunnion end of the cylinder. Torque the
valves to 45-50 lb-ft (61-68 Nm). Refer to the Parts
Manual for seal kits.
IMPORTANT: DO NOT tamper with or attempt to reset
the counterbalance valve cartridge. If adjustment or
replacement is necessary, replace a counterbalance
valve with a new part.
16. Test the cylinder at low operating pressure
(100 psi or 7 bar). Verify that the piston and the rod
move freely in both directions.
17. Increase the operating pressure to the maximum
amount for the cylinder (4000 psi or 275 bar) and
again check for free movement in both directions.
18. Retract the rod fully into the tube and cap and plug
the hydraulic hose ports.
g. Extend/Retract Cylinder Installation
Installation procedures are covered in Section 3.3.1,
“Inner Boom Replacement.”
h. Extend/Retract Cylinder Pressure Checking and
Circuit Bleeding
1. Attach a 5000 psi (345 bar) gauge to the main
control valve to test the extend/retract cylinder
hydraulic system circuit pressure. The unit is
equipped with test fittings from the factory. Refer to
Section 8.7, “Hydraulic System Testing.”
2. With no accessory installed on the quick attach, start
with the lift/lower and attachment tilt cylinders fully
retracted.
3. Fully extend the extend/retract cylinder. Hold the
joystick at full extend while fully raising the lift/lower
cylinder.
4. Fully retract the attachment tilt cylinder. Hold the
attachment tilt joystick at full retract while fully
retracting the lift/lower cylinder.
5. Repeat Steps 3 thru 4 five times.
8.14.7 Lift/Lower Cylinder
The lift/lower cylinder (26) is anchored to the underside of
the outer boom and to the front of the transfer carriage.
a. Lift/Lower Cylinder Removal
1. Park the vehicle on a firm, level surface, fully retract
all hydraulic cylinders, place the travel select lever in
the [N] NEUTRAL DETENT position, engage the
park brake switch, raise and support the boom to
allow removal of the lift/lower cylinder and shut the
engine OFF.
2. Place an Accident Prevention Tag on both the
ignition switch and the steering wheel, stating that
the vehicle should not be operated. Refer to Section
1.5, “Accident Prevention Tag Usage.”
3. Unlatch and open the engine cover. Allow the
hydraulic fluid to cool.
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.
WARNING:
Hot hydraulic fluid can
cause severe burns. Wait for hydraulic fluid to
cool before servicing any hydraulic component.
MU3670
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