Kubota U25-3 Repair Manual

U20-3, U25-3 WSM Hydraulic system (Service section)
IV-S-4
b. Hydraulics
Problem Cause Correction
The entire hydraulic system fails
or responds too slow or too
weak.
(1) Hydraulic oil too short in the tank or oil
degraded.
Add or change the hydraulic oil.
(2) Suction line (suction filter) clogged.
Check the suction line and replace the
suction filter as required.
(3) Pump coupling defective. Repair or replace the pump coupling.
(4) Pump drive shaft broken. Replace the shaft.
(5) Pump internal parts seized or damaged. Repair or replace the pump.
The boom, arm, bucket and
swivel mechanism fail or
respond too slow or too weak.
(1) Hydraulic pilot filter or hydraulic pilot line filter
clogged.
Clean or replace the pilot filter.
(2) Selector valve defective. Overhaul or replace the selector valve.
(3) Pilot pump internal parts seized or damaged. Replace the pilot pump.
The boom, bucket and right-
travel mechanism fail or respond
too slow or too weak.
(1) Main relief valve (P1) not at specified
pressure.
Check the main relief valve (P1) and
readjust as required.
(2) P1 or P2 line pump internal parts seized or
damaged if the arm, service port and left-travel
mechanism fail too.
Overhaul or replace the pump.
The arm, service port and left-
travel mechanism fail or respond
too slow or too weak.
(1) Main relief valve (P2) not at specified
pressure.
Check the main relief valve (P2) and
readjust as required.
(2) P1 or P2 line pump internal parts seized or
damaged if the boom, bucket and right-travel
mechanism fail too.
Overhaul or replace the pump.
The swing, dozer and swivel
mechanism fail or respond too
slow or too weak.
(1) Main relief valve (P3) not at specified
pressure.
Check the main relief valve (P3) and
readjust as required.
(2) P3 line pump internal parts seized or
damaged.
Overhaul or replace the pump.
The boom alone fails or
responds too slow or too weak.
(1) Boom overload relief valve not at specified
pressure.
Check the overload relief valve and repair
as required.
(2) Control valve or boom section spool
malfunctioning.
Check the spool and repair as required.
(3) Pilot valve defective.
Measure the secondary pressure and
check the pilot valve.
(4) Boom cylinder rod packing broken.
Overhaul the cylinder and replace the
sealing.
The arm alone fails or responds
too slow or too weak.
(1) Arm overload relief valve not at specified
pressure.
Check the overload relief valve and repair
as required.
(2) Control valve or arm section spool
malfunctioning.
Check the spool and repair as required.
(3) Pilot valve defective.
Measure the secondary pressure and
check the pilot valve.
(4) Arm cylinder rod packing broken.
Overhaul the cylinder and replace the
sealing.
The bucket alone fails or
responds too slow or too weak.
(1) Bucket overload relief valve not at specified
pressure.
Check the overload relief valve and repair
as required.
(2) Control valve or bucket section spool
malfunctioning.
Check the spool and repair as required.
(3) Pilot valve defective.
Measure the secondary pressure and
check the pilot valve.
(4) Bucket cylinder rod packing broken.
Overhaul the cylinder and replace the
sealing.

Kubota U25-3 Specifications

General

Brand	Kubota
Model	U25-3
Category	Excavators
Language	English