Maintenance - Manitowoc Grove RT770E Service Maintenance Manual

RT770E

Maintenance

Troubleshooting
Table 8-4
Symptom
1. Slow or erratic operation of
o u t r i g g e r e x t e n s i o n
cylinders.
1. Slow or erratic operation of
o u t r i g g e r e x t e n s i o n
cylinders. (continued)
GROVE
Probable Cause
a. Damaged relief valve.
b. Low hydraulic oil.
c. Sticking solenoid valve spool.
d. Improper ground to base of
solenoid.
e. Directional selector
sticking.
f. Collector ring dirty or glazed.
g. Damaged wiring to solenoid.
h. Weak brush springs
collector ring.
i. Damaged extension cylinder
(internal parts).
j. Bent cylinder rods.
k. Excessive material
outrigger beams.
l. Binding outrigger beam.
m. Damaged outrigger valve.
n. Damaged valve coil.
o. Main hydraulic pump
cavitation.
p. Partially shifted hydraulic
spool in selector valve or
manifolds.
q. Insufficient voltage
operation of solenoid valve.
r. Damaged piston seals.
s. Worn or damaged hydraulic
pump section.
t. Scored cylinder barrel.
u. Cracked or damaged piston.
Published 11/26/2014, Control # 447-05
Solution
a. Remove
replace.
b. Check system for leaks. Make
repairs as needed. Fill reservoir.
c. Repair or replace valve spool.
d. Ground properly.
switch e. Clean or replace switch.
f. Clean and deglaze collector ring.
g. Replace wiring.
on h. Replace brush springs.
i. Remove extension cylinder and
repair as necessary.
j. Replace piston rods and seals.
on k. Clean outrigger beams.
l. Repair or replace outrigger beam.
m. Repair or replace valve.
n. Replace coil.
o. Replace or tighten hose or fitting.
Refer to your Manitowoc Crane Care
Parts Manual.
p. Disassemble,
spool and valve housing with very
fine emery cloth (water paper).
for q. Solenoids require a minimum of 9.5
volts to energize. Check outrigger
w i r i n g a n d e l e c t r i c a l c o u p l i n g
collector rings.
r. Replace all cylinder seals.
s. Repair or replace pump section.
t. Repair or replace extension cylinder.
u. Replace rod weld and all cylinder
seals.
UNDERCARRIAGE
relief valve; clean or
clean, and polish
8-27
8