Manitowoc Grove RT770E Service Maintenance Manual

BOOM RT770E SERVICE MANUAL
4-42
Published 11/26/2014, Control # 447-05
3. Boom raises
slowly.
a. Low hydraulic oil level. a. Check system for leaks. Make repairs
as needed. Fill reservoir.
b. Low engine rpm. b. Increase and maintain engine rpm.
c. Damaged relief valve. c. Repair or replace relief valve.
d. Extremely cold hydraulic oil. d. Operate unit to bring oil to operating
temperature.
e. Improper hose or fittings, installed. e. Replace hose or fittings. (Refer to
Manitowoc Crane Care Parts Manual).
f. Operating two functions with in the
same control valve bank assembly.
f. Feather controls to obtain desired
speed of both functions.
g. Restriction in return hose. g. Replace return hose.
h. Cylinder piston seals leaking. h. Replace all cylinder seals.
i. Scored cylinder barrel. i. Hone or replace barrel.
j. Worn hydraulic pump section. j. Repair or replace pump section.
4. Boom lowers
slowly.
a. Low hydraulic oil level. a. Check system for leaks. Make repairs
as needed. Fill reservoir.
b. Low engine rpm. b. Increase rpm to recommended level.
c. Damaged relief valve. c. Repair or replace relief valve.
d. Operating two functions within the
same control valve bank assembly.
d. Feather controls to obtain desired
speed of both functions.
e. Extremely cold hydraulic oil. e. Operate unit to bring oil to operating
temperature.
f. Improper hose or fittings installed. f. Replace hose or fittings. (Refer to
Manitowoc Crane Care Manual).
g. Restriction in return hose. g. Replace return hose.
h. Cylinder piston seals worn. h. Replace all cylinder seals.
i. Scored cylinder barrel. i. Hone or replace barrel.
j. Worn hydraulic pump section. j. Repair or replace pump section.
k. Piston rod broken (loose from piston). k. Replace piston rod and all cylinder
seals.
5. Boom will not
raise. a. Low hydraulic oil. a. Check system for leaks. Make repairs
as needed. Fill reservoir.
b. Main relief valve or circuit relief valve
damaged.
b. Repair or replace relief valve.
c. Excessive load. c. Reduce load as required.
d. Worn or damaged hydraulic pump
section.
d. Repair or replace pump section.
e. Broken pump shaft. e. Replace pump shaft and seals.
f. Broken pump drive coupling. f. Replace drive coupling.
g. Broken control valve spool. g. Replace control valve.
Symptom Probable Cause Solution

Manitowoc Grove RT770E Specifications

General

Brand	Manitowoc
Model	Grove RT770E
Category	Construction Equipment
Language	English