Manitowoc Grove 5540F Service Manual page 112

HYDRAULIC SYSTEM
main relief housing and if grooves and ridges are evident, the
valve must be replaced.
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The design of the pilot poppet and its seal provides positive
seating and very seldom requires any maintenance.
Therefore, the pilot section can be removed from the
cartridge housing without disturbing the pressure setting.
Relief Valve Troubleshooting
PROBLEM
Can't get pressure.
Erratic Pressure.
Pressure setting not correct.
Leaks.
Anti-Void Assembly
Trouble resulting in a malfunctioning anti-void valve
Figure 4-47 can usually be traced back to foreign matter
plugging the sensing hole or preventing free movement of
the poppet. Also, check seat for scratches, nicks or other
marks.
4-48
With it will come the check valve poppet and other internal
parts. These are easily disassembled and should be
examined for foreign material. All seats and seating surfaces
should be smooth and free of nicks, scratches or grooves.
Examine o-rings and backup washers for any damage and
replace if necessary. All moving parts should slide freely, with
oil seal friction being present.
After inspecting and cleaning, immerse all parts in hydraulic
oil and reassemble. Since the pressure setting was not
disturbed, the relief valve can be tested for proper function
under actual working conditions.
If operating difficulties, indicate that the pilot poppet is
leaking or sticking, remove internal parts of the pilot section,
and follow the same procedure as above. After assembly,
FIGURE 4-46
adjust the relief valve pressure per instructions in this
section.
If the relief valve still does not function properly, replace the
relief valve.
PROBABLE CAUSE
Poppet D, E, or K stuck open or
contamination under seat.
Pilot poppet seat damaged.
Poppet C sticking in D.
Normal wear. Lock nut and adjusting
screw loose.
Damaged seats.
Worn o-ring.
Parts sticking due to contamination.
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Published 10-21-2010, Control# 198-04
5540F/YB5515 SERVICE MANUAL
REMEDY
Check for foreign matter between
poppets D, E or K and their mating
parts. Parts must slide freely.
Replace the relief valve.
Clean and remove surface marks for
free movement.
Adjust pressure.
Replace the relief valve.
Install new seal and spring kit.
Disassemble and clean.
Anti-Void Valve
FIGURE 4-47