SkyTrak 8042 Service Manual - Manual (Page 550)

8.135 Model 8042, 10042, 10054 Legacy Rev. 10/03
Hydraulic System
IMPORTANT: Avoid using excess force when clamping
the cylinder in a vise. Apply only enough force to hold the
cylinder securely. Excessive force can damage the
cylinder tube (18).
10. Secure the lift/lower cylinder in a soft-jawed vise or
other acceptable holding equipment if possible.
11. Lubricate the inside of the tube (18) and outside of
the piston (5) and head gland (7) with clean, filtered
hydraulic oil.
12. Apply a compression sleeve or other suitable tool to
the head gland (7) and piston (5) in order to
compress the o-rings, back-up rings and seals, while
inserting the assembled piston, rod and head gland
into the tube (18).
IMPORTANT: When sliding the rod (2) and piston
assembly into the tube, prevent the threaded end of the
tube from damaging the piston (5). 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 (2) with all attachments
straight into the tube (18).
14. Using a pin spanner wrench, thread the locking
collar (19) onto the tube (18). Torque the locking
collar to 300-400 lb-ft (407-542 Nm).
IMPORTANT: DO NOT tamper with or attempt to reset
the counterbalance valve cartridge (20). If adjustment or
replacement is necessary, replace a counterbalance
valve with a new part.
15. Lubricate the counterbalance valve (20) and the
pilot-operated check valve (21) with clean, filtered
hydraulic oil. Using new oiled o-rings, thread the
valves into tube (18). Torque to 30-35 lb-ft (41-47 Nm).
16. Test the cylinder at low operating pressure 100 psi
(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 3000 psi (207 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.
f. Lift/Lower Cylinder Installation
1. Raise and support the boom to allow installation of
the lift/lower cylinder.
2. Attach a sling to the lift/lower cylinder and to a hoist
or an overhead crane. Safely and carefully, position
the lift/lower cylinder inside the frame aligning the
rod and base eyelets with mounting bosses of the
boom and frame.
3. Secure the cylinder with cylinder mount pins,
capscrews and nuts.
4. Connect all hoses according to the labels or other
marks used to identify their locations during removal.
5. Operate the vehicle in order to check all boom
functions and check for hydraulic system leaks.
6. Wipe up any hydraulic fluid spillage in, on, near and
around the vehicle. Perform the pressure check and
circuit bleeding procedure below.
g. Lift/Lower Cylinder Pressure Checking and
Circuit Bleeding
1. Attach a 4000 psi (276 bar) gauge to the test fitting
on the main control valve to test the system
pressure. Pressure readings should be
3000 ±100
psi (207 ±7 bar). Refer to Section 8.7, “Hydraulic
System Testing.” To check each cylinder pressure,
consult the factory.
2. With no accessory installed on the quick attach, start
with the lift/lower and attachment tilt cylinders fully
retracted.
3. Fully raise and fully extend the boom. Hold the
joystick at full extend, while fully raising the lift/lower
cylinder.
4. Fully retract the attachment tilt cylinder. Hold the
joystick at full retract, while fully lowering the boom.
5. Repeat Steps 3 and 4 five times.
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:
Escaping hydraulic fluid
under pressure can penetrate the skin, causing
death or serious injury.