HYDRAULIC SYSTEM GRT8100 SERVICE MANUAL
2-56
Published 3/26/2018, Control # 596-05
LIFT CYLINDER AND TELESCOPE
CYLINDER CONTROL VALVES
Description
A externally-piloted cartridge style holding valve is installed
on the lift cylinder and a cartridge style holding valve is
installed into each telescope cylinder port block.
Maintenance
Removal
1. Start the engine and fully retract the telescope the lift
cylinders using the joysticks. Use the RCL override
function to fully retract the lit cylinder.
2. Shut off engine.
3. Unscrew holding valve from its port block or manifold.
Installation
1. Check inside of port block or manifold for sharp edges or
burrs. Remove as necessary with emery cloth.
2. Install new O-rings on holding valve.
3. Lubricate holding valve O-rings with clean hydraulic oil.
NOTE: Holding valve should turn by hand until O-rings
compress.
4. Carefully install holding valve into port block or manifold
until fully seated.
5. Test holding valve and port block or manifold by
operating lift cylinder and/or telescope cylinder, as
applicable. Verify lift cylinder and/or telescope cylinder
works without problems; verify there is no leaking. Make
repairs as needed.
WARNING
Falling Boom
Never remove a holding valve from the lift or telescope
cylinder circuits without first fully retracting the cylinders.
Death or serious injury can occur.
WARNING
High Hydraulic Pressure
Never remove a holding valve from the lift or telescope
cylinder circuits without first fully retracting the cylinders to
remove the high hydraulic pressure in the circuits. Fluid in
these hydraulic systems can be under enough pressure
that it will penetrate the skin, causing serious injury or
death.
CAUTION
Do not damage O-rings during holding valve installation. If
holding valve turns freely then hard to turn, then easy to
turn, remove holding valve and check O-rings. They have
probably been damaged by a sharp edge of a port.
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