HYDRAULIC SYSTEM 5540F/YB5515 SERVICE MANUAL
4-44 Published 10-21-2010, Control# 198-04
Main Control Valves
General
The main control valves are designed with very close
tolerances between the spools and the valve bores. Dirt,
chips or sludge can cause these surfaces and seals to wear
and result in internal leakage, sticking or both. A thorough
cleaning of the valve and replacement of seals will generally
remedy a leaking problem. Extreme care must be taken
when disassembling and assembling valves to prevent nicks
or scratches in machined surfaces. All spools must be
installed in their original bores. If a spool or valve bore is
damaged, the entire valve section must be replaced.
Removal
1. Shut off the engine and relieve all hydraulic pressure in
lines and hoses connected to the valve.
2. Thoroughly clean the outside of the valve and
surrounding tube lines.
3. Disconnect, mark for assembly and plug all lines and
hoses attached to the valve assembly.
4. Remove t he four bolts, washers, lockwashers and nuts
securing the valve mounting plate to the dash.
5. Loosen and remove the four bolts, washers,
lockwashers and nuts securing the valve assembly to
the mounting plate. Remove the valve and take to clean
work area.
Disassembly
Complete Valve Assembly
NOTE: Although the following procedures are for
disassembling the three-spool main control valve,
the procedures may be used for disassembling the
one-spool main control valve.
1. Place the valve assembly on the work bench with the
outlet section facing up.
2. Remove the three nuts from the studs at the outlet
section 16 Figure 4-42.
3. Lift off the outlet section 16 from the studs.
4. Lift off boom lift spool section 8.
5. Lift off mid-inlet section 15.
6. Lift off winch spool section 8.
7. Lift off mid-inlet sections 14 and 13.
8. Lift of outrigger spool section 9.
9. Lift off the telescope spool section 8.
10. Lift off mid-inlet section 6.
11. Lift off swing spool section 5.
12. Remove the tie rods 17 from the outlet section 2.
13. Remove and discard all o-rings 3 from the valve
sections.
Spool Valve Sections
1. Remove the load check spring 4 Figure 4-43 and load
check poppet 3.
2. Remove the handle assembly from the spool valve
section.
3. Remove the seal plate 7 and remove and discard the
wiper seal 6 and o-ring 5.
4. Loosen and remove the two hex socket cap screws 16.
Remove the seal plate 11 and cap 15.
5. Slowly loosen screw 14. The screw is under spring
pressure be sure to hold the spring seats 12 and spring
13 when removing screw 14.
6. Remove spring seats 12, spring 12 and screw 14.
7. Remove and discard o-ring 9 and wiper seal 10.
Assembly
Spool Valve Sections
1. If the valve spool was removed from the valve housing,
apply a good grade of petroleum jelly to the spool and
then insert the spool into the housing.
2. Coat all seals with a light coat of hydraulic oil, then install
o-ring 9 Figure 4-43, wiper seal 10.
3. Install one of the spring seats 12 over the valve spool.
Install spring 13 and the other spring seat 12. Install
screw 14 and tighten to a torque of 7 lb-ftl (9.52 Nm).
4. Locate cap 15 and seal plate 11 over the spring
assembly and secure to the valve housing with two hex
socket capscrews 16. Tighten to a torque of 7 lb-ft
(9.52 Nm).
CAUTION
Be careful when separating the valve sections. The three
spool sections have spring-loaded load check
assemblies. The spring could fly out of the valve section
when the section is removed.
Reference Only
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