Lull 944E-42 Service Manual - Manual (Page 136)

Hydraulic System
8-20 944E-42
Disassemble each Valve Section
1. Carefully separate the inlet section (12) from the transfer
carriage section (13).
2. Remove and discard o-rings from between the two
sections.
3. Carefully separate transfer section (13) from the
auxiliary hydraulic section (14).
4. Remove any relief valves (15), the unloader valve
(16), spool end housings (17) or compensators (18)
from individual valve section if equipped.
Note: The internal parts of the relief valves and
unloader valves are not serviceable. Replace the entire
relief/unloader valve if necessary.
Note: The spool in the section is not serviceable
separately. If the spool is scratched or nicked the entire
section must be replaced.
Note: The plungers of the compensators are not
serviceable. If these parts require replacement the entire
section must be replaced.
Mono Block Disassembly
The mono block section (19) contains the relief valves,
spools and compensators for the attachment tilt (20),
frame sway (21), boom lift/lower (22) and boom extend/
retract functions (23).
1. Remove the relief valves (24) from the appropriate
function.
2. Remove the spool end housings (25) and
compensators (26) from the appropriate function.
Note: The internal parts of the relief valves are not
serviceable. Replace the entire relief valve if necessary.
Note: The spool in the section is not serviceable
separately. If the spool is scratched or nicked the entire
mono block must be replaced.
Note: The plungers of the compensators are not
serviceable. If these parts require replacement the entire
mono block must be replaced.
c. Main Control Valve Parts Cleaning
Clean all components with a suitable cleaner, such as
triclorethylene, before continuing. Blow dry.
d. Main Control Valve Parts Inspection
Inspect all parts and internal passageways for wear,
damage, etc. If inner surfaces of any component DO NOT
display an ultra-smooth, polished finish, or are damaged
in any way, replace the damaged part. Often, dirty
hydraulic fluid causes failure of internal seals, damage to
the polished surfaces within the component, and wear of
and/or harm to other parts.
e. Main Control Valve Assembly
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.
Mono Block Assembly
1. Install the spring and plunger into the spool end
housing (25). Place the spool end housing on the
end of the spool. Secure the spool end housing to
the mono block and install two capscrews. Repeat
for the other spool end housings on the mono block.
2. Install the appropriate relief valves (24) into the
appropriate function. The two relief valves for the
attachment tilt section are preset to 4000 psi
(276 bar). The relief valve in the extend/retract
section is preset to 2900 psi (200 bar). Torque the
relief valves to 33 ± 3.5 lb-ft (45 ± 4,8 Nm).
3. Place the lower compensator plunger followed by the
spring and the upper compensator plunger (26) into
the cavity on top of the mono block. Secure in place
with the hex plug and new oiled o-ring. Torque the
plug to 48 ± 5 lb-ft (65 ± 7 Nm). Repeat for the other
compensators on the mono block.
Inlet Section Assembly
1. Install the main relief valve (15) into the side of the
inlet section. Torque the main relief valve to 33 ± 3.5
lb-ft (45 ± 4,8 Nm).
2. Install the unloader valve (16) into the side of the
inlet section. Torque the unloader valve to 48 ± 5 lb-ft
(65 ± 7 Nm).
3. Insert the four hex socket head capscrews through
the inlet section.
Transfer Carriage Section Assembly
1. Install the relief valve (15) preset to 3700 psi
(255 bar) into the “A” side of the transfer carriage
section. Torque the relief valve to 33 ± 3.5 lb-ft
(45 ± 4,8 Nm).