SECTION 6 WORK EQUIPMENT

Group 1 Structure and Function ----------------------------------------------------------------------------------- 6-1

Group 2 Operational Checks and Troubleshooting ----------------------------------------------------- 6-40
Group 3 Tests and Adjustments ----------------------------------------------------------------------------------- 6-51
Group 4 Disassembly and Assembly --------------------------------------------------------------------------- 6-64
 SECTION 6 WORK EQUIPMENT
GROUP 1 STRUCTURE AND FUNCTION

1. HYDRAULIC SYSTEM OUTLINE

The loader hydraulic system is a pilot operated, closed center system which is supplied with flow
from the variable displacement piston main hydraulic pump.
The loader system components are :
ÂMain pump
ÂMain control valve
ÂBucket cylinder
ÂBoom cylinders
ÂRemote control valve (Pilot control valve, EH type)
ÂSafety valve

Flow from the main hydraulic pump not used by the steering system leaves the steering valve
(EHPS) EF port.
It flows to the inlet port plate of two section or three section block type main control valve.
The main control valve is load pressure independent flow distribution system which routes flow to the
boom, bucket or auxiliary cylinders (not shown) when the respective spools are shifted.
Flow from the main pump is routed to the main control valve where pump outlet pressure is reduced
to pilot circuit pressure. The main control valve flow to the remote control valve.
The remote control valve routed flow to either end of each spool valve section in the main control
valve to control spool stroke.
A accumulator mounted on safety valve supplies a secondary pressure source to operated remote
control valve so the boom can be lowered if the engine is off.
The return circuit for the main hydraulic system have return filter inside the hydraulic tank. The return
filter uses a filter element and a bypass valve. The bypass valve is located in the upside of filter.

6-1
 2. HYDRAULIC CIRCUIT
13 12
28

PS
RH

36
Sp. T
28

PS
35
a2 a3
LS

T P a1 A1 B1 A2 B2 pst A3 B3
3

Down Floating
B

Dump
A

Rollback
Bucket Boom Aux

Up
S1
14

LH RH
S2
9 b1 A2 B2
7 Bucket Boom 40
Aux LH
b2 b3
4 Joystick
39 Control unit
12
B.D/F B.U B.I DUMP

CL CR
5
8' 8 39 Control unit
ELECTRONICS
(Electro-Hydraulic & joystick steering) T P

2 4
L
41 1 3 4 2 1.1
EH18 EH17 EH20 EH19 EH22 EH21
T
R 40 a2 b2 b2
P B/Down B/up Aux down
1 3 b1 a1
B/in Dump T
4 1 6(4) 3(2) 5(3) 2(1) ( ) : 2 Spool
Ps
FRONT
To MCV
P1
Ts
A1
a3 b3 a1 b1 a2 b2 T1
EF P LS T
P2 20 AXLE
A2
T2
A1
27 27 10 16 16 19
L
6
R
B2 S2 S3
17 18 REAR
S1 B1

S1
15 PS

37
X2 G1
X1 P1 T
Parking
X3 P
11 B3
T/M
2 4
PS

18
PS

P T 18
PS
G2 38
3 1
PP T1 T2
32 1 X1 X2 22
34 28 PS
S
P 26
33
PS

M T
P1
23 30
B1 B2
24 2 D 29
P A A

31 M 25 B B
B T

S1 L2 L1 S2 L4 L3
21
S1 L 760F6WE01

1 Main pump 14 Steering cylinder 28 Pressure sensor

2 Fan & brake pump 15 Cut-off valve 29 Fan motor
3 Main control valve 16 Accumulator 30 Directional valve
4 RCV (EH type) 17 Accumulator 31 Pump motor (opt)
5 RCV (FNR type, opt) 18 Pressure sensor 32 Check block (opt)
6 Steering unit 19 Brake valve 33 Pressure sensor (opt)
7 Accumulator 20 Pressure switch 34 Check valve (opt)
8 Steering valve (EHPS) 21 Hydraulic tank 35 Ride control valve (opt)
8' Electric steering valve (opt) 22 Air breather 36 Accumulator (opt)
9 Joystick steering lever (opt) 23 Return filter 37 Quick coupler cylinder (opt)
10 Safety valve 24 By pass valve 38 Solenoid valve (opt)
11 Shuttle valve 25 Strainer 39 Control unit
12 Boom cylinder 26 Oil cooler 40 EH control block
13 Bucket cylinder 27 Check valve 41 Boom lowering valve
6-2
 HYDRAULIC CIRCUIT (DIRECT STEERING, OPT)
40
T Sp. 39
AUX1 BUCKET BOOM
11 11 16 15
Joystick
23
RH
PS 23
PS
8 Control Unit / Electro Hydraulic

EH18 EH17 EH20 EH19 EH22 EH21 10 T

B
a2 a3
LS A
P
3 T P a1 A1 B1 A2 B2 pst A3 B3
X X
X
x

DOWN FLOATING
4 1 6 3 5 2 3spool
2spool

BUCKET
4 2 3 1

BOOM
)(

DUMP
a3 b3 a1 b1 a2 b2 To
Aux Aux Bucket Bucket Boom Boom MCV
Down Up Dump In Down Up

ROLLBACK

UP
17 X X S1

X X X S2
LH RH B2
b1 A2
21 21
9 b2 b3

22 22 15
LH

18
10 B.D/F B.U CRAWD DUMP AUX
L

T P 24
1 3 4 2 1.1 2.1 FRONT
R
P1
HYD

A1
T1
T
EH
P2 25 AXLE
P A2
T2
LS A1
7 7 27 27 28
REAR
19 CF EF
29
S1 B1 B2 S2 S3 PS

LS S1
26 C5 C6 G1
X1 X2 P1 T C3 PARKING 41
13 C1
C4
X3 P
P T 14 29 B3
42
PS

T/M 2 4
PS C2
PS

G2
PP T1 T2 29 3 1

36 1 X1 X2 31
S 38 23 PS
6
P
37
PS

M T
P1
B1 B2
32 33 2 5 D 4
A
35 P

M
DURTRI

34 B
B
T

S1 L2 L1 S2 L4 L3
30
9656WE01A
S1 L

1 Main pump 14 Shuttle valve 29 Pressure sensor

2 Fan & brake pump 15 Boom cylinder 30 Hydraulic tank
3 Main control valve 16 Bucket cylinder 31 Air breather
4 RCV (EH type) 17 Steering cylinder 32 Return filter
5 RCV (FNR type, opt) 18 Steering unit 33,34 By pass valve, Strainer
6 Steering unit 19 Steering valve 35 Pump motor (opt)
7 Check valve 21 Accumulator 36 Check block (opt)
8 Steering valve (EHPS) 22 Orifice 37 Pressure sensor (opt)
9 Boom lowering valve 23 Pressure sensor 38 Check valve (opt)
10 EH control block 24 Brake valve 39 Ride control valve (opt)
11 Control unit 25 Pressure switch 40 Accumulator
12 Remote control valve 26 Cut-off valve 41 Quick coupler cylinder (opt)
13 Safety valve 27,28 Accumulator 42 Solenoid valve (opt)
6-2-1
 3. WORK EQUIPMENT HYDRAULIC CIRCUIT

13 12
28

PS
RH

28

PS
a2 a3
LS

3 T P a1 A1 B1 A2 B2 pst A3 B3

Down Floating
Aux Bucket Boom

Dump
4 Joystick
5
39

Roll back
Control unit Bucket Boom Aux
(Electro-Hydraulic & Joysick steering)

Up
S1
EH18 EH17 EH20 EH19 EH22 EH21
T
40
P

S2
4 1 6(4) 3(2) 5(3) 2(1) ( ) : 2 Spool b1 A2 B2

To MCV LH
b2 b3

a3 b3 a1 b1 a2 b2 12
41
A1
Steering valve 27 27 10
(EHPS) EF port
Steering valve S1
(EHPS) LS port X1 X2 P1 T
X3
11
Return line

1 X1 X2 22 Return line
Steering system
28 PS

B1 B2 23
24
25
S1 L2 L1 S2 L4 L3
21
Fan & brake pump

760F6WE02

1 Main pump 11 Shuttle valve 25 Strainer

3 Main control valve 12 Boom cylinder 27 Check valve
4 Remote control valve 13 Bucket cylinder 28 Pressure sensor
(EH type) 21 Hydraulic tank 39 Control unit
5 Remote control valve 22 Air breather 40 EH control block
(FNR type, opt) 23 Return filter 41 Boom lowering valve
10 Safety valve 24 Bypass valve

6-3
 1) WHEN THE RCV LEVER IS IN THE RAISE POSITION

13 12
28

PS
RH

28

PS
a2 a3
LS

3 T P a1 A1 B1 A2 B2 pst A3 B3

Down Floating
Aux Bucket Boom

Dump
4 Joystick
5
39

Roll back
Control unit Bucket Aux
(Electro-Hydraulic & Joysick steering) Boom

Up
S1
EH18 EH17 EH20 EH19 EH22 EH21
T
40
P

S2
4 1 6(4) 3(2) 5(3) 2(1) ( ) : 2 Spool b1 A2 B2

To MCV LH
b2 b3

a3 b3 a1 b1 a2 b2 12
41
A1
Steering valve 27 27 10
(EHPS) EF port
Steering valve S1
(EHPS) LS port X1 X2 P1 T
X3
11
Return line

1 X1 X2 22 Return line
Steering system
28 PS

B1 B2 23
24
25
S1 L2 L1 S2 L4 L3
21
Fan & brake pump
7609FWE03

 When the RCV lever (4, boom) is pulled back, the boom spool is moved to raise position by pilot oil
pressure from EH control block (40).
 The oil from main pump (1) flows into main control valve (3) and then goes to the large chamber of
boom cylinder (12).
 The oil from the small chamber of boom cylinder (12) returns to hydraulic oil tank (21) through the
boom spool at the same time.
 When this happens, the boom goes up.

6-4
 2) WHEN THE RCV LEVER IS IN THE LOWER POSITION

13 12
28

PS
RH

28

PS
a2 a3
LS

3 T P a1 A1 B1 A2 B2 pst A3 B3

Floating
Down
Aux Bucket Boom

Dump
4 Joystick
5
39

Roll back
Control unit Bucket Boom Aux
(Electro-Hydraulic & Joysick steering)

Up
S1
EH18 EH17 EH20 EH19 EH22 EH21
T
40
P

S2
4 1 6(4) 3(2) 5(3) 2(1) ( ) : 2 Spool b1 A2 B2
Regeneration
check valve
To MCV LH
b2 b3

a3 b3 a1 b1 a2 b2 12
41
A1
Steering valve 27 27 10
(EHPS) EF port
Steering valve S1
(EHPS) LS port X1 X2 P1 T
X3
11
Return line

1 X1 X2 22 Return line
Steering system
28 PS

B1 B2 23
24
25
S1 L2 L1 S2 L4 L3
21
Fan & brake pump

760F6WE04

Â
When the RCV lever (4, boom) is pushed forward, the boom spool is moved to lower position by
pilot pressure from EH control block (40).
 The oil from main pump (1) flows into main control valve (3) and then goes to small chamber of
boom cylinder (12).
 The oil returned from large chamber of boom cylinder (12) returns to hydraulic tank (21) through
the boom spool at the same time.
 When the lowering speed of boom is faster, the return oil from the large chamber of boom cylinder
combines with the oil from the pump through the regeneration check valve, and flows into the small
chamber of the cylinder.
This prevents cylinder cavitation by the negative pressure when the pump flow cannot match the
boom down speed.

6-5
 3) WHEN THE RCV LEVER IS IN THE FLOAT POSITION

13 12
28

PS
RH

28

PS
a2 a3
LS

3 T P a1 A1 B1 A2 B2 pst A3 B3

Floating
Down
Aux Bucket Boom

Dump
4 Joystick
5
39

Roll back
Control unit Bucket Boom Aux
(Electro-Hydraulic & Joysick steering)

Up
S1
EH18 EH17 EH20 EH19 EH22 EH21
T
40
P

S2
4 1 6(4) 3(2) 5(3) 2(1) ( ) : 2 Spool b1 A2 B2

To MCV LH
b2 b3

a3 b3 a1 b1 a2 b2 12
41
A1
Steering valve 27 27 10
(EHPS) EF port
Steering valve S1
(EHPS) LS port X1 X2 P1 T
X3
11
Return line

1 X1 X2 22 Return line
Steering system
28 PS

B1 B2 23
24
25
S1 L2 L1 S2 L4 L3
21
Fan & brake pump

760F6WE05

 When the RCV lever (4, boom) is pushed further forward from the lower position, the pilot pressure
reaches to 13~15bar, then the boom spool is moved to floating position.
 The work ports (A2), (B2) and the small chamber and the large chamber are connected to the
return passage, so the boom will be lowered due to it's own weight.
 In this condition, when the bucket is in contact with the ground, it can be move up and down in
accordance with the shape of the ground.

6-6
 4) WHEN THE RCV LEVER IS IN THE DUMP POSITION

13 12
28

PS
RH

28

PS
a2 a3
LS

3 T P a1 A1 B1 A2 B2 pst A3 B3

Down Floating
Dump
Aux Bucket Boom
4 Joystick
5
39

Roll back
Control unit Bucket Boom Aux
(Electro-Hydraulic & Joysick steering)

Up
S1
EH18 EH17 EH20 EH19 EH22 EH21
T
40
P

S2
4 1 6(4) 3(2) 5(3) 2(1) ( ) : 2 Spool b1 A2 B2
Regeneration
check valve LH
To MCV b2 b3

a3 b3 a1 b1 a2 b2 12
41
A1
Steering valve 27 27 10
(EHPS) EF port
Steering valve S1
(EHPS) LS port X1 X2 P1 T
X3
11
Return line

1 X1 X2 22 Return line
Steering system
28 PS

B1 B2 23
24
25
S1 L2 L1 S2 L4 L3
21
Fan & brake pump

760F6WE06

 If the RCV lever (4, bucket) is pushed right, the bucket spool is moved to dump position by pilot oil
pressure from EH control block (40).
 The oil from main pump (1) flows into main control valve (3) and then goes to the small chamber of
bucket cylinder (13).
 The oil at the large chamber of bucket cylinder (13) returns to hydraulic tank (21).
 When this happens, the bucket is dumped.
 When the dumping speed of bucket is faster, the oil returned from the large chamber of bucket
cylinder combines with the oil from the pump, and flows into the small chamber of the cylinder.
This prevents cylinder cavitation by the negative pressure when the pump flow cannot match the
bucket dump speed.

6-7
 5) WHEN THE RCV LEVER IS IN THE ROLL BACK (retract) POSITION

13 12
28

PS
RH

28

PS
a2 a3
LS

3 T P a1 A1 B1 A2 B2 pst A3 B3

Down Floating
Aux Bucket Boom

Dump
4 Joystick
5
39

Roll back
Control unit Bucket Boom Aux
(Electro-Hydraulic & Joysick steering)

Up
S1
EH18 EH17 EH20 EH19 EH22 EH21
T
40
P

S2
4 1 6(4) 3(2) 5(3) 2(1) ( ) : 2 Spool b1 A2 B2
Regeneration
check valve LH
To MCV b2 b3

a3 b3 a1 b1 a2 b2 12
41
A1
Steering valve 27 27 10
(EHPS) EF port
Steering valve S1
(EHPS) LS port X1 X2 P1 T
X3
11
Return line

1 X1 X2 22 Return line
Steering system
28 PS

B1 B2 23
24
25
S1 L2 L1 S2 L4 L3
21
Fan & brake pump

760F6WE07

 If the RCV lever (4, bucket) is pulled left, the bucket spool is moved to roll back position by pilot oil
pressure from EH control block (40).
 The oil from main pump (1) flows into main control valve (3) and then goes to the large chamber of
bucket cylinder.
 The oil at the chamber of bucket cylinder (13) returns to hydraulic tank (21).
 When this happens, the bucket roll back.

6-8
4. MAIN PUMP
1) STRUCTURE (1/2)
This variable displacement piston pump consists of steering pump and loader pump.

L1 X1 B1 L3 X2 B2

L2 S1 L4 S2

X1 X2

B1 B2

E/G

S1 L2 L1 S2 L4 L3
Hydraulic circuit

76096WE88

Port Port name Port size

B1 Pressure port SAE 1"
B2 Pressure port SAE 1"
S1 Suction port SAE 2"
S2 Suction port SAE 2"
L1, L2 Case drain port 1 1/16-12UN-2B
L3, L4 Case drain port 1 1/16-12UN-2B
X1, X2 Pilot pressure port 7/16-20UNF-2B

6-9
Â MAIN PUMP (1/2, STEERING)
10
24

27
23

6,31

37

2 16
12
51
53
33 52
1-2
54

30 1-1

7
17
22

15
20
25 76096WE11

1 Rotary group 12 Adjustment shim 27 Socket screw

1-1 High speed rotary group 15 Taper roller bearing 30 Locking screw
1-2 Control plate 16 Taper roller bearing 31 Double break-off pin
2 Adjusting piece 17 Bearing liner 33 Cylinder pin
5 Pump housing 20 Shaft seal ring 37 Side mark ring
6 Port plate 22 O-ring 51 Control valve
7 Swash plate 23 O-ring 52 Gasket
8 Drive shaft 24 O-ring 53 Socket head screw
10 Splined hub 25 Retaining ring 54 Locking screw

6-10
Â MAIN PUMP (2/2, LOADER)

28

27
23

6,31
2
2

41
11
43 16
33 42 12

44 1-2

1-1
30

7
17
22

8
15
20
25
76096WE12

1 Rotary group 12 Adjustment shim 28 Locking screw

1-1 High speed rotary group 15 Taper roller bearing 30 Locking screw
1-2 Control plate 16 Taper roller bearing 31 Double break-off pin
2 Adjusting piece 17 Bearing liner 33 Cylinder pin
5 Pump housing 20 Shaft seal ring 41 Control valve
6 Port plate 22 O-ring 42 Gasket
7 Swash plate 23 O-ring 43 Socket screw
8 Drive shaft 25 Retaining ring 44 Locking screw
11 Adjustment shim 27 Socket screw

6-11
2) FUNCTION

1 2 3 4 5 6

LS pressure

12 13
X

11

8 9 10 L B

X L1 S

13 12 4 10
75796WE33

1 Drive shaft 6 Counter spring 11 Control plate

2 Swash plate 7 Pressure & flow compensator valve 12 Pressure compensator spool
3 Shoe plate 8 Piston shoe 13 Flow compensator spool
4 Counter piston 9 Cylinder
5 Piston 10 Control piston

The steering pump and loader pump are variable displacement piston pump. The steering pump
and loader pump are flow controlled by LS signal. When the steering and loader are not being
used, the pumps are at low pressure standby.
The load sensing pressure that is sensed from steering and loader hydraulic systems flows to flow
compensator spool (13). This spool keeps the pump output at a level that is necessary to fulfill the
requirements for the system flow and for the pressure.
The pressure compensator spool (12) also limits maximum system pressure. The pressure
compensator spool (12) prevents damage to the steering and loader hydraulic components from
excessive pressure.
The swivel angle of the pumps is controlled by counter piston (4) and control piston (10). Counter
spring (6) cause swash plate (2) to move at maximum displacement or causes swash plate (2) to
upstroke.
Control piston (10) has a larger area (diameter) than counter piston (4). Control piston (10) causes
swash plate (2) to destroke the pump.
Flow compensator spool (13) and/or pressure compensator spool (12) changes pump output by
regulating the pump discharge pressure that is acting on control piston (10).

6-12
Control piston (10) diameter is larger than counter piston (4) diameter, the oil pressure that is
acting against control piston (10) overcomes the force of counter spring (6). The oil pressure than
causes the pump to destoke.
Pressure and flow compensator valve (7) also controls the maximum output of pump pressure.
When steering and loader pressure rises above pressure compensator setting, pressure
compensator spool (12) overrides flow compensator spool (13). This causes the pump to destroke.

6-13
(1) Upstroking
14
1 2 4 6

15

LS pressure

12 13
X

21

22
10 L B

16

LS pressure oil
System pressure oil
Return oil L1 S
4 10
17 18 19 20 13 23 12
75796WE35

1 Drive shaft 13 Flow compensator spool 19 LS line from the metering pump
2 Swash plate 14 Case drain 20 Cavity
4 Counter piston 15 Passage 21 Passage
6 Counter spring 16 Passage 22 Passage
10 Control piston 17 Spring 23 Cavity
12 Pressure compensator spool 18 Spring

Upstroking of the pump occurs as flow demand from loader and steering system.
The increased flow demand causes a LS pressure in LS line (19). The LS pressure in LS line (19)
combines with the force of spring (18) in cavity (20).
The force of spring (18) causes pump pressure to be higher than the LS pressure (19).
If the combination of LS pressure and of spring force is greater than the pump discharge pressure,
this difference pressure causes spool (13) to move right. As spool (13) moves right, the spool (13)
blocks the flow of supply oil to control piston (10). Pump swash plate (2) is controlled by pressure
and flow as much as hydraulic system requests.
When the oil flow to control piston (10) is blocked, the pilot oil in passage (22) drains to passage
(23). The oil then flows past pressure compensator spool (12) and through passage (16) into the
housing and via the drain line (14) to tank.
Supply oil flows through passage (15) to counter piston (4). The oil acts against counter piston (4).
The oil combines with the force of counter spring (6). This causes swash plate (2) to upstroke.
This also causes the pump flow to increase. As flow requirements are satisfied, the pump output
pressure increase. The pressure increases until the pressure in passage (15) moves flow
compensator spool (13) up to be satisfied with system requirement for pressure and flow.
ÂPump discharge pressure = force of spring (18) + LS pressure (19)

6-14
(2) Destroking

14
1 2 4 6

15

LS pressure

12 13
X

21

22
10 L B

16

LS pressure oil
System pressure oil
Return oil L1 S
4 10
17 18 19 20 13 23 12
75796WE34

1 Drive shaft 13 Flow compensator spool 19 LS line from the metering pump
2 Swash plate 14 Case drain 20 Cavity
4 Counter piston 15 Passage 21 Passage
6 Counter spring 16 Passage 22 Passage
10 Control piston 17 Spring 23 Cavity
12 Pressure compensator spool 18 Spring

The decreased flow demand causes a LS pressure in line (19). The LS pressure in line (19)
combines with the force of spring (18) in cavity (20).
This combination of LS pressure and of spring force is less than the pump pressure in passage
(21). This causes flow compensator spool (13) to move left.
Pump oil now flows through passage (15). The oil then flows past flow compensator spool (13),
through passage (22), and then to control piston (10).
The pump pressure behind control piston (10) is now greater than the combined force of counter
piston(4) and of counter spring (6). The angle of swash plate (2) decreases.
This decreases the pump output and the system pressure.
When the lower flow requirements are met, flow compensator spool (13) moves right up to the
balanced position. Swash plate (2) maintains an angle that is sufficient to provide the lower
required pressure. If the operator does not turn the steering wheel and does not move RCV, then
the pump will return to low pressure standby.
୔ Control piston ˧ Changes pump displacement ; influenced by controller.
Counter piston ˧ Helps to change pump displacement but no possible to control this piston.

6-15
(3) Low pressure standby

14
1 2 4 6

15

LS pressure

12 13
X

21

22 L
10 24 B

16

LS pressure oil
System pressure oil
Return oil L1 S
4 10
17 18 19 20 23 13 12
75796WE36

1 Drive shaft 13 Flow compensator spool 19 LS line from the metering pump
2 Swash plate 14 Case drain 20 Cavity
4 Counter piston 15 Passage 21 Passage
6 Counter spring 16 Passage 22 Passage
10 Control piston 17 Spring 23 Cavity
12 Pressure compensator spool 18 Spring 24 Cross-drilled hole

Low pressure standby constitutes the following condition: a running engine and inactive steering
and loader. There are no flow demands on the pump or pressure demands on the pump.
Therefore, there is no LS pressure in line (19).
Before you start the engine, counter spring (6) holds swash plate (2) at the maximum angle. As the
pump begins to turn, oil begins to flow and pressure increases in the system.
Because of close centered steering control valve and close centered loader hydraulic system.
As this pressure increase, the pressure pushes flow compensator spool (13) against spring (18).
This causes flow compensator spool (13) to move left. This opens passage (23) in order to allow
pressure oil to flow to control piston (10).
The oil acts against control piston (10) in order to overcome the force of counter spring (6). The oil
causes control piston (10) to move to the left.
When control piston (10) moves to the left, the piston moves swash plate (2) toward the minimum
angle. Control piston (10) continues to move to the left until cross-drilled hole (24) allows the oil to
drain to the case.

6-16
 Cross-drilled hole (24) limits the maximum travel of control piston (10) to the left. The pump
supplies a sufficient amount of flow that compensates for system leakage. The pump also supplies
a sufficient of flow that compensates for leakage to the pump case. The leakage to the pump case
is a result of the cross-drilled hole. The pump maintains low pressure standby. Low pressure
standby pressure should not exceed 40 bar (580 psi).
ö Low pressure standby will vary in the same pump as the system leakage or the pump leakage
increases. The pump will upstroke slightly in order to compensate for the increasing leakage.
Control piston (10) will cover more of the cross-drilled hole.

6-17
(4) High pressure stall

14
1 2 4 6

15

LS pressure

12 13
X

21

22 L
10 24 B

16

LS pressure oil
System pressure oil
Return oil L1 S
4 10
17 18 19 20 23 13 12
75796WE36

1 Drive shaft 13 Flow compensator spool 19 LS line from the metering pump
2 Swash plate 14 Case drain 20 Cavity
4 Counter piston 15 Passage 21 Passage
6 Counter spring 16 Passage 22 Passage
10 Control piston 17 Spring 23 Cavity
12 Pressure compensator spool 18 Spring

When the hydraulic system stalls under load or when the cylinders reach the end of the stroke, the
main system pressure increases. But LS pressure (19) is regulated by LS relief valve on steering
system and loader system. The pressure difference between discharged pump and LS pressure
equal to spring (18). It means no flow is necessary. Therefore, discharged pressure push flow
compensator spool (13) left . Supply oil now flows past flow compensator spool (13) and through
passage (23). The oil flows past flow compensator spool (13) and into passage (22). The oil then
flows to control piston (10).
Pump swash plate (2) will be minimum displacement if the operator does not turn the steering
wheel and RCV, then the pump will return to low pressure standby.

6-18
(5) Adjustment of flow control
Flow compensator setting must be carried out following procedures and conditions.
Η Conditions
- Engine is running (at high or low idle).
- RCV is operated slowly (example : Boom up).
- Pressure gauges are installed.
ö Discharge pump flow should be less than max pump flow.

Θ Procedures

- Loosening the hexagon nut (2).
- Adjusting screw (1) of flow controller by tightening or loosing the screw (1).
ÂFlow setting : ȟP = Gauge A - Gauge B
ÂSpecification : Steering pump (32 bar) / Loader pump (20 bar)

Flow compensator Gauge B

X
2 1
Gauge A
-16 bar/rev
+16 bar/rev B

S L1 L
75796WE37

(6) Adjustment of pressure control

Pressure compensator setting must be carried out following procedures and conditions.
Η Conditions
- Engine is running.
- System is at relief condition.

Θ Procedures
- Loosening the hexagon nut (2).
- Adjusting screw (1) of pressure controller by tightening or loosing the screw (1).
ÂMaximum pressure setting = Gauge A
ÂSpecification : Steering pump (250 bar) / Loader pump (300 bar)
Pressure compensator
X

Gauge A

-52 bar/rev
+52 bar/rev

S L1 L
2 1 75796WE38

6-19
5. EH (electro hydraulic) CONTROL BLOCK
1) STRUCTURE
10-4 10-5 10-6

Proportional pressure
reducing valve
10-1 10-2 10-3

T DS

1 2 3 Filter screen

4 5 6

EH18 EH17 EH20 EH19 EH22 EH21

T Port Size
P 9/16-18UNF
1~6
DS 9/16-18UNF
P,T 3/4-16UNF
10-4 10-1 10-6(4) 10-3(2) 10-5(3) 10-2(1)

4 1 6 (4) 3 (2) 5 (3) 2 (1) DS ( ) : 2-spool

760F6WE33
Hydraulic circuit
2) OPERATION
The proportional pressure reducing valve
(10-1~6) is a direct-acting spool-type valve.
When de-energized, port 2 is closed and
port 1 (delivery) is connected to port 3
(tank). When the inlet pressure fluctuates it
provides an almost constant outlet 1
pressure-depending on the energization of
the coil. When the control current
3 2
increases, the coil solenoid exerts a force
on the control piston which is proportional
to the control current and thereby defines
the regulated pressure at port 1. This
3
setting is proportional to the control current.
Pressures at tank port 3 are additive to the 2
set pressure. If, as a result of external
1 7809A6WE33
factors, the pressure at port 1 rises above
the preset pressure, the valve opens from
port 1 to tank port 3.
6-20
6. MAIN CONTROL VALVE
1) STRUCTURE (1/3)
ÂType : Closed center, Load pressure - Independent - Flow - Distribution

a3 b3
A3 B3
LS
pst
a2 b2
A2 B2

a1 b1
A1 B1
P

a2 a3
LS

T P a1 A1 B1 A2 B2 pst A3 B3
Down Floating
Dump
Roll back

Bucket Boom Aux

Up

S1

S2
b1 A2 B2

b2 b3

Hydraulic circuit

76096WE10

Port Port name Port size

P From main pump SAE 1"
T To hydraulic tank SAE 1 1/4"
A1, B1 To bucket cylinder port SAE 3/4"
A2, B2 To boom cylinder port SAE 3/4"
a1, b1 Bucket pilot port 11/16-16UN
a2, b2 Boom pilot port 11/16-16UN
a3, b3 Auxiliary pilot port 11/16-16UN
LS Load sensing port 9/16-18UNF
Pst To RCV P port 9/16-18UNF

6-21
 STRUCTURE (2/3)

61

62

60

36 38
38
37
79

35
50

79
74
33
31

33 32
79

30

86
102 71

84
74

11
79
85
165
76096WE13

11 Housing 37 O-ring 74 Compensator valve

30 O-ring 38 O-ring 79 Pressure valve
31 O-ring 50 Housing 84 Flow regulator
32 O-ring 60 Plate 85 Precharge valve
33 O-ring 61 Cylinder screw 86 Pilot oil supply
35 O-ring 62 Washer 102 Locking screw
36 O-ring 71 Shuttle valve 165 Pressure relief valve

6-22
 STRUCTURE (3/3)

23
21
91
12
90 96
96
12 90 20
21 91
23 39

23
50 21
20
39 13

95
40 91 19
90
90 91
96 34 23
12
21
23
20
20
12
34
96
34 90
40
91
41 34

91
90 11
96

21
23

12

20

76096WE14

11 Housing 21 Throttle check valve 50 Housing

12 Cover 23 Threaded steel pipe fitting 90 Compression spring
13 Cover 34 O-ring 91 Spring retainer
14 Cover 39 O-ring 95 Spring retainer
19 Bolt 40 Spool 96 Spring retainer
20 Bolt 41 Spool

6-23
2) FUNCTION

4
6
A B

a T P b

A B
2 5 3 1 7

a2 3
LS

T P a1 A1 B1 A2 B2 pst
Down Floating
Dump
Roll back

Bucket Boom
Up

b1 A2 B2

4 6
b2

Hydraulic circuit

76096WE15

1 Housing 4 Counter balance valve 7 Spring chamber

2 Spool 5 Regeneration check valve
3 Pressure compensator 6 Port relief valve

6-24
(1) Control block
Proportional direction valve to the LUDV principle (Load pressure - Independent - Flow -
Distribution)
(2) Actuator control
At the spool (2) the direction and volume of flow is determined that flows to the actuator
connections (A or B).
The spring chambers (7) are supplied with pilot pressure either via the pilot connections a and b
hydraulic control.
The value of the pilot pressure within the spring chamber (7) determines the stroke of the spool
(2).
The pressure compensator (3) controls the pressure differential at the spool (2) and therefore, the
flow to the actuators (A, B).
(3) Loader pressure compensation (LUDV)
The control block works to the LUDV principle. In this load - sensing version the pressure
compensators (3) are located between the spool (2) and the actuator connections (A, B).
The highest load pressure of all of the actuators involved is applied to all of the pressure
compensators. In parallel it is also applied to the pump.
If the pump flow is insufficient for all of the functions, then all work movements are reduced in
speed by the same ratio.
(4) Pressure safety, actuator connections
Large nominal size port relief valve (6) with combined anti-cavitation functions protect the
actuators from overloads and cavitation.
(5) Float position
The float position is obtained by means of a 4-position spool.
(6
(6)) Regeneration
To prevent cavitation, with negative loads (e. g. dump or lowering), the tank port is pre-loaded via
counter balance valve (4) and is fed with oil via the regeneration check valve (5) downstream of
the pressure compensator.

6-25
3) BOOM SECTION OPERATION
(1) Spool in neutral

A2 B2

a2 T P b2

A2 B2

a2
LS

T P a1 A1 B1 A2 B2 pst
Down Floating
Dump
Roll back

Bucket Boom
Up

b1 A2 B2

b2

Hydraulic circuit
76096WE51

When the boom spool is in neutral position, oil from the pump will be blocked.
Then, the pumps are at low pressure stand by.

6-26
(2) Boom raise position

A2 B2

a2 T P b2

A2 B2

a2
LS

T P a1 A1 B1 A2 B2 pst
Down Floating
Dump

Boom
Roll back

Bucket
Up

b1 A2 B2

b2

Hydraulic circuit
76096WE52

When the pilot pressure is led to the port b2, the boom spool moved to raise position.
Oil from the pump flows to the cylinder port B2 and oil from the cylinder flows into the tank
passage through the cylinder port A2.

6-27
(3) Boom lower position

A2 B2

a2 T P b2

A2 B2

a2
LS

T P a1 A1 B1 A2 B2 pst
Down
Dump

Boom
Roll back

Bucket 6
Up

b1 A2 B2

b2

Hydraulic circuit
76096WE53

When the pilot pressure is led to the port a2, the boom spool moved to lower position.
Oil from the pump flows to the cylinder port A2 and oil from the cylinder flows into the tank
passage through the cylinder port B2.
When the lowering speed of boom is faster, the return oil from the large chamber of boom
cylinder combines with the oil from the pump through regeneration check valve (6), and flows into
the small chamber of the cylinder. This prevents cylinder cavitation by the negative pressure when
the pump flow cannot match the boom down speed.

6-28
(4) Boom float position

A2 B2

a2 T P b2

A2 B2

a2
LS

T P a1 A1 B1 A2 B2 pst
Dump

Floating

Boom
Roll back

Bucket
Up

b1 A2 B2

b2

Hydraulic circuit
76096WE54

When the boom spool is located in float position, the oil from the pump will be blocked.
The cylinder ports (A2, B2) are connected to the tank passage, so the boom will be lowered due
to it's own weight.

6-29
4) BUCKET SECTION OPERATION
(1) Spool in neutral

A1 B1

T P b1
a1

a2
LS

T P a1 A1 B1 A2 B2 pst
Down Floating
Dump
Roll back

Bucket Boom
Up

b1 A2 B2

b2

Hydraulic circuit
76096WE55

When the bucket spool is in neutral position, oil from the pump will be blocked.
Then, the pumps are at low pressure standby.

6-30
(2) Bucket rollback position

A1 B1

a1 T P b1

a2
LS

T P a1 A1 B1 A2 B2 pst
Down Floating
Dump

Roll back

Bucket
Boom
Up

b1 A2 B2

b2

Hydraulic circuit
76096WE56

When the pilot pressure is led to the port b1, the bucket spool moved to rollback position.
Oil from the pump flows to the cylinder port B1 and oil from the cylinder flows into the tank
passage through the cylinder port A1.

6-31
(3) Bucket dump

A1 B1

T P b1
a1

6 a2
LS

T P a1 A1 B1 A2 B2 pst
Down Floating
Dump

Bucket
Roll back

Boom
Up

b1 A2 B2

6
b2

Hydraulic circuit
76096WE57

When the pilot pressure is led to the port a1, the bucket spool moved to dump position.
Oil from the pump flows to the cylinder port A1 and oil from the cylinder flows into the tank
passage through the cylinder port B1.
When the dumping speed of bucket is faster, the return oil from the large chamber of bucket
cylinder combines with the oil from the pump through regeneration check valve (6), and flows into
the small chamber of the cylinder. This prevents cylinder cavitation by the negative pressure when
the pump flow cannot match the bucket dump speed.

6-32
7. SAFETY VALVE
1) STRUCTURE

2
4

5
P1

T
A1
A1

3 2
1

P1 T
Hydraulic circuit

Port Port name Port size

P1 From MCU PF 3/8"
A1 Supply to RCV lever PF 1/4"
T To hydraulic tank PF 1/4"
75796WE16

1 Bowl and element assy 4 Solenoid valve

2 Check valve 5 Accumulator
3 Cartridge

2) OPERATION
This valve is used to cut off the pilot circuit.
When the pilot cut off switch in the cab is pressed to ON position, the solenoid valve is activated
and then the pilot oil flow into the pilot circuit.
The accumulator satisfied short term peak power demands and is a source of emergency power in
case of main circuit pressure failures.

6-33
8. BOOM AND BUCKET CYLINDER
The boom cylinders are two unit and the bucket cylinder is one unit. They use a bolt on rod guide.
The piston (14) threads on to the rod (2) and is retained by a nut (20) and set screw (21).
The piston seals against the tube (1) with piston seal (15). Two wear rings (16) are located on each
side of the piston seal.
The gland (3, the rod guide) seals against the tube with an O-ring (12). The cylinder thread seals
against the rod with a lip type buffer ring (8) and a rod seal (6). A dust wiper (9) cleans the rod when
it is retracted.
1) BOOM CYLINDER

22 30, 31 23, 24

25 26 29

6, 7 12 , 13 18,19
9,10 3 8 11 4, 5 1 2 14 17 16 15 20 21 28 27

760F6WE17

1 Tube assembly 12 O-ring 23 Pin bushing

2 Rod assembly 13 Back up ring 24 Dust seal
3 Gland 14 Piston 25 Pipe assembly
4 Bushing 15 Piston seal 26 Pipe assembly
5 Snap ring 16 Wear ring 27 O-ring
6 Rod seal 17 Dust ring 28 Socket bolt
7 Back up ring 18 O-ring 29 Band assembly
8 Buffer ring 19 Back up ring 30 Hexagon bolt
9 Dust wiper 20 Lock nut 31 Spring washer
10 Snap ring 21 Set screw
11 O-ring 22 Socket bolt

6-34
2) BUCKET CYLINDER

26 25

23 , 24

22

27

6, 7 12 , 13
9,10 3 8 11 4, 5 1 2 14 17 16 15 18,19 20 21

29 28
760F6WE18

1 Tube assembly 11 O-ring 21 Set screw

2 Rod assembly 12 O-ring 22 Socket bolt
3 Gland 13 Back up ring 23 Pin bushing
4 Bushing 14 Piston 24 Dust seal
5 Snap ring 15 Piston seal 25 Band assembly
6 Rod seal 16 Wear ring 26 Pipe assembly
7 Back up ring 17 Dust ring 27 Pipe assembly
8 Buffer ring 18 O-ring 28 O-ring
9 Dust wiper 19 Back up ring 29 Socket bolt
10 Snap ring 20 Lock nut

6-35
9. HYDRAULIC OIL TANK
1) STRUCTURE
 The oil from the hydraulic tank is sent from the pump through main control valve to the cylinders.
In the return circuit, the oil from various parts merges.
 A part of oil is cooled in the oil cooler, passes through the hydraulic filter and returns to the
hydraulic tank (1).
 If the hydraulic return oil filter becomes clogged, return filter bypass valve (6) acts to allow the oil
to return directly to the hydraulic tank (1). This prevents damage to the hydraulic filter (5). The
bypass valve (6) is also actuated when negative pressure is generated in the circuit.

13 1 Hydraulic tank wa
2 Pipe wa
13 11 3 Sight gauge
11 12
4 Air breather
5 Element assembly
15 6 Bypass valve
12
6 7 Spring
7 8 O-ring
9 Socket bolt
5
10 Bolt
14 11 Cover
12 O-ring
13 Bolt
9
14 Strainer
15 Spring

10
9656WE21

6-36
2) RETURN OIL FILTER BYPASS VALVE
(1) When the filter is clogged
Bypass valve (1) is opened and the oil
1
returns directly to the tank without
passing through the filter.
ÂBypass valve set pressure : 1.36 kg/cm2
(19.3 psi)

From MCV
770-3ATM (6-33)

6-37
3) AIR BREATHER
The air breather is equipped with the
capacity to perform three functions
simultaneously-as an air filter, breathing
valve, and as a lubrication opening.
(1) Preventing negative pressure inside the
Air breather
tank
The tank is a pressurized sealed type, so
negative pressure is formed inside the
hydraulic tank when the oil level drops
during operations. When this happens,
the difference in pressure between the
tank and the outside atmospheric
pressure opens the poppet in the
breather, and air from the outside is let
into the tank or prevent negative pressure.
(2) Preventing excessive pressure inside
the tank
When the hydraulic cylinder is being
used, the oil level in the hydraulic system
increases and as temperature rises. If
the hydraulic pressure rises above the set
pressure, breather is actuated to release
the hydraulic pressure inside the tank. 9656WE22

6-38
10. ACCUMULATOR
The accumulator is installed at the safety
valve. When the boom is left the raised
position, and the control levers are operated
with the engine stopped the pressure of the
compressed nitrogen gas inside the
accumulator sends pilot pressure to the
control valve to actuate it and allow the boom
1
and bucket to come down under their own 2
weight.
3
Type of gas Nitrogen gas (N2)
Volume of gas 0.75˶(0.2 U.S.gal)
Charging pressure of gas 16 kg/cm2 (228 psi)
Max actuating pressure 128 kg/m2 (1820 psi)
1 Diaphragm
2 Steel pressure vessel
3 Closure button
7803AWE56

6-39
11. RIDE CONTROL SYSTEM (option)
1) ACCUMULATORS
(1) Pre-charging
Use an inert gas such as nitrogen for pre-charging
accumulator.
侍 Do not use oxygen or shop air.
侍 Nitrogen source and all components must be
rated for a pressure at least as high as the
nitrogen source.

Accumulator having gas valve as per figure 1.

刮 Remove gas valve guard and gas valve cap. Valve core
刯 Back gas chuck "T" handle (A) all the way out
(counter clockwise) before attaching charging &
gauging kit to accumulator gas valve.
到 Close bleed valve (B).
刱 Making sure not to loop or twist the hose,
attach swivel nut (C) to gas valve and tighten
11.5~17 kgf·cm (10~15 lbf·ft).
刲 Turn gas chuck "T" handle (A) until the gauge
Figure 1
starts showing the pressure in the accumulator.
WLACC01
Do not turn the "T" handle all the way down, as
it will damage the valve core.
刳 Crack open nitrogen bottle valve (D) and slowly
fill accumulator. Shut off when gauge indicates
desired pre-charge.
刴 Let the pre-charge set for 10 to 15 minutes.
This will allow the gas temperature to stabilize.
If the desired pre-charge is exceeded, close
B
nitrogen bottle valve (D), then slowly open
bleed valve (B). Do not reduce pre-charge by A
depressing valve core with a foreign object.
High pressure may rupture rubber valve seat. C
刵 When finished pre-charging accumulator, turn
"T" handle (A) all the way out on gas chuck, D
then open bleed valve (B). Charging and gauging kit (31LM-90100)
制 Hold gas valve to keep from turning, loosen
WLACC02
swivel nut (C), remove assembly. Check for pre
-charge leak using a common leak reactant.
刷 Replace gas valve cap 11.5~17 kgf·cm (10~15
lbf·ft) and valve guard. (Gas valve cap serves as
a secondary seal.)
(2) Pre-charge checking procedure
Using appropriate valve in the hydraulic system,
discharge all oil from accumulator and allow
piston to bottom against hydraulic end cap.

6-39-1
6-40
 (3) Structure

2 1 4 3 9A 8

8A 9

5 6 7 7A

5A
WLACC03

1 Body 5A V-O-ring back-up washers 8A Gas valve O-ring

2 Hydraulic cap 6 Piston ring (piston) 9 Gas valve guard
3 Gas cap 7 O-ring 9A Screw
4 Piston 7A O-ring back-up washer
5 V-O-ring 8 Gas valve

2) REMOVE FROM HYDRAULIC SYSTEM

Attention
1) Before carrying out any maintenance work the B
accumulators must be unloaded (zero pressure).
A
2) For this, loosen the nut (4) and bolt (B)
counterclockwise with 10 mm spanner.
侍 The accumulator will be unloaded (zero pressure)
in less than a minute.
3) The lifting system must firstly be secured against
lowering.
4) After carrying out maintenance work, screw the
bolt (B) and nut (A).
余Tightening torque Ride control valve
A : 2.04 kgf余m (14.8 lbf余ft)
7609A6WE28

6-39-2
6-41
GROUP 2 OPERATIONAL CHECKS AND TROUBLESHOOTING

1. OPERATIONAL CHECKS
This procedure is designed so the mechanic can make a quick check of the system using a minimum
amount of diagnostic equipment. If you need additional information, read structure and function,
Group 1.
A location will be required which is level and has adequate space to complete the checks.
The engine and all other major components must be at operating temperature for some checks.
Locate system check in the left column and read completely, following the sequence from left to right.
Read each check completely before performing.
At the end of each check, if no problem is found (OK), that check is complete or an additional check is
needed. If problem is indicated (NOT OK), you will be given repair required and group location.
If verification is needed, you will be given next best source of information:

ÂChapter 2 : Troubleshooting


ÂGroup 3 : Tests and adjustments

6-40
侍 Hydraulic oil must be at operating temperature for these checks (refer to page 6-55).
Item Description Service action
Hydraulic system warm-up Hold a hydraulic function over relief OK
procedure to heat oil. (don't keep relief Check completed.
condition over 5 seconds at a time)
Run engine at high idle.
Refer to page 6-55. Periodically cycle all hydraulic
functions to distribute warm oil.
Repeat procedure until oil is at
operating temperature.
FEEL : Hydraulic reservoir must be
uncomfortable to hold your hand
against.
(approximately 40 ~50˚C)
Hydraulic pump With bucket flat on ground, actuate OK
performance check boom raise. Time how long it takes Check completed.
to raise boom to full height.
H e a t hy d r a u l i c o i l t o NOT OK
operating temperature. LOOK : Boom must raise to full Go to priority valve (in
Run engine at high idle. height in less than 7 seconds. s t e e r i n g va l ve ) h i g h
pressure check at page
5-26.
IF OK
Do steering system
leakage check at page
5-27.
IF OK
Do main hydraulic pump
flow test at page 6-56.
Control valve lift check With bucket partially dumped, OK
Run machine at low idle. lower boom to raise front of Check complete.
machine.
NOT OK
Slowly move boom control lever Repair lift checks in loader
( R C V l eve r ) t o b o o m l ow e r control valve.
position.
Slowly move bucket control lever to
bucket dump position.
LOOK : Boom must not raise
before moving down.
Bucket must not rollback before
dumping.

6-41
 Item Description Service action
Bucket rollback circuit relief Position bucket at a 45˚ angle OK
valve check against an immovable object. Check complete.
Engage transmission in 3rd speed NOT OK
forward. Replace boom lower
check valve.
LOOK : Bucket angle must not
change.
Bucket dump circuit relief Raise front of machine which OK
valve low pressure check bucket at 45˚ angle. Go to next check.
Backdrag with bucket while NOT OK
observing bucket angle. Do loader system and
circuit relief valve test at
LOOK : Bucket must not rollback
page 6-57.
Pilot control valve float With the bucket partially dumped, OK
check lower boom to raise front of Check complete.
machine.
Run engine at low idle. NOT OK
Push control lever to the float
Do pilot control valve
detent position and release lever.
pressure test in group 3.
LOOK : Front of machine lower to
the ground and valve must remain
in float position when lever is
released.

Boom cylinder and S e t t h e b o o m a n d b u c k e t OK

bucket cylinder dr ift horizontal, then stop the engine. Check complete.
check
Stop the engine, wait for 5 NOT OK
H e a t hy d r a u l i c o i l t o minutes, then start measuring. Go to next check.
operating temperature.
Measure the amount the lift and
dump cylinder rods retract during
15 minutes. (unloaded bucket)
B A : Retraction of boom cylinder
rod
A
B : Retraction of bucket cylinder
rod
Boom cylinder must drift less than
15 mm
Bucket cylinder must drift less
than 24 mm

6-42
 Item Description Service action
Boom cylinder leakage Dump bucket until teeth or cutting OK
check edge is perpendicular to the Drift is approximately the
ground. same between first and
H e a t hy d r a u l i c o i l t o
second measurement.
operating temperature. Raise boom until cutting edge is
about 1 m (3 ft) above ground.
Repair loader control
Stop engine. Measure drift from valve or circuit relief valve.
tooth or cutting edge to ground for
1 minute. NOT OK
If drift is considerably less
Wait 10 minutes.
on second measurement,
Measure drift from tooth or cutting repair cylinder.
edge to ground for 1 minute.
LOOK : Compare the drift rate
between the first measurement
and the second measurement.
Bucket cylinder leakage Raise bucket about 1 m (3 ft) off OK
check ground with bucket level. Drift is approximately the
same between first and
H e a t hy d r a u l i c o i l t o Stop engine.
second measurement.
operating temperature. Place a support under boom.
Measure drift from tooth or cutting Repair loader control
edge to ground for 1 minute. valve or circuit relief valve
at page 6-57.
Wait 10 minutes.
Measure drift from tooth or cutting NOT OK
edge to ground for 1 minute. Drift is considerably less
on second measurement.
LOOK : Compare the drift rates
between the first measurement
Repair cylinder.
and the second measurement.
Check valve of safety Put bucket level and position OK
valve leakage check about 1.2 m (4 ft) above ground. Check complete.
H e a t hy d r a u l i c o i l t o Place a piece of tape on cylinder
NOT OK
operating temperature. rod at least 51 mm (2 in) from rod
Check or replace safety
guide.
valve.
Run engine at low idle in safety-
release position.
LOOK : Bucket must not drift up.
Pilot control valve Stop engine. OK
Turn key switch to OFF position. Check completed.
(RCV lever) check
Move control lever to all positions
NOT OK
and then release.
Repair pilot control valve.
LOOK : Lever must return to
neutral when released from all
positions.

6-43
 Item Description Service action
Bucket leveler Position bucket fully dumped just OK
(positioner) check above ground level. Check complete.
Run engine at low idle. Move control lever to bucket NOT OK
leveler detent position and Do bucket leveler checks.
release.
LOOK : Bucket must rollback to
the level position and control lever
must return to neutral.
If bucket is in a rolled back
position when key is turned ON,
control lever must be returned to
neutral manually if placed in the
bucket leveler detent position.
After bucket is dumped once,
bucket leveler will work normally.
Boom height kickout Position bucket flat on ground. OK
check Check complete.
Move control lever to boom raise
Run engine at low idle. detent position and release. NOT OK
Do boom height kickout
LOOK : Boom must raise to the
check.
set height and stop.
Control lever must return to
neutral.
Cycle time check Function Operating condition. Maximum cycle time
H e a t hy d r a u l i c o i l t o Boom raise Bucket flat on ground to full 5.8sec
operating temperature. height.
Run engine at high idle.
Boom lower Full height to level ground. 3.1sec
Bucket dump Boom at full height. 1.4sec
Bucket rollback Boom at full height. 1.8sec
Steering [No. of Frame stop to frame stop. 3.8 turns
turns]
OK
Check complete.
NOT OK
Go to slow hydraulic
functions in group 2.

6-44
侍 MEASURING BOOM AND BUCKET CYCLE TIME
1) MEASUREMENT CONDITION
ÂCoolant temperature : Inside operating range
ÂSteering position : Neutral
ÂHydraulic temperature : 40~50˚C
ÂBucket : Unloaded
ÂEngine speed : High idling

2) MEASURING TOOL
 Stop watch (1EA)

3) MEASURING PROCEDURE
Lifting time of boom
(1) LIFTING TIME OF BOOM
Set the bucket near the maximum tilt back
position and at the lowest position on the
ground.
Raise the bucket and measure the time
taken for bucket to reach the maximum
height of the boom.
7609A6WE25

(2) LOWERING TIME OF BOOM

Set the bucket horizontal with the boom at Lowering time of boom
the maximum height, lower the bucket and
measure the taken for the bucket to reach
the lowest position on the ground.

7609A6WE26

(3) DUMPING TIME OF BUCKET

Raise the boom to the maximum height Dumping time of bucket
Rollback time of bucket
and measure the time taken for the bucket
to move from the maximum tilt back
position to the maximum dump position
(4) ROLL BACK TIME OF BUCKET
Raise the boom to the maximum height
and measure the time taken for the bucket
to reach the maximum tilt back position. 7609A6WE27

6-45
2. TROUBLESHOOTING
侍 Diagnose malfunction charts are arranged from most probable and simplest to verify, to least
likely, more difficult to verify. Remember the following steps when troubleshooting a problem :

Step 1. Operational check out procedure (see section 1)

Step 2. Operational checks (see group 2)
Step 3. Troubleshooting
Step 4. Tests and adjustments (see group 3)

Problem Cause Remedy

Noisy hydraulic pump Low oil supply or wrong viscosity. Fill reservoir with recommended oil.
Plugged or pinched suction line. Clean or replace line.
Air in oil. Check for foamy oil.
Tighten connections.
Replace O-rings and or lines.
Plugged suction strainer. Inspect and clean strainer in reservoir.
Loose or missing hydraulic line clamps. Tighten or replace clamps.
Hydraulic lines in contract with frame. Inspect and repair.
Worn or damaged pump. Do hydraulic pump performance check
in group 2. Do hydraulic pump flow test
in group 3.
No or Slow hydraulic Failed or worn hydrualic pump. Do performance check.
functions
Cold oil. Warm oil up.
Slow engine speed. Adjust engine speed.
Check high idle speed.
Suction line air leak. Check for foamy oil.
Low oil supply. Add recommended oil.
Wrong oil viscosity. Use recommended oil.
Oil leaking past cylinders or control Check cylinder drift in group 2.
valve.
Blocked or damaged line. Inspect lines.

Faulty pilot control valve (RCV). Do pilot control valve (RCV) pressure
test in group 3.
Binding loader control valve (MCV) Inspect valve.
spool.
Faulty steering valve (EHPS). Check priority valve, orifice of steering
valve (EHPS) specification.

6-46
 Problem Cause Remedy
No steering or hydraulic Low oil level. Add recommended oil.
function
Failed hydraulic pump. Remove and inspect return filter for
metal pump particles.
No hydraulic functions Failed hydraulic pump. Remove and inspect return filter for
steering normal metal pump particles, or replace the
pump.
Failed line filter. Remove and inspect line filter for RCV.
Faulty safety valve. Safety valve leakage test or ON, OFF
function test.
Stuck open port relief valve. Replace relief valve.
Boom float function Low pilot control pressure. Do pressure reducing valve pressure
does not work test in group 3.
Faulty pilot control valve (RCV). Replace relief valve.
Loader control valve (MCV) spool Do pressure reducing valve pressure
binding in bore. test in group 3.
One hydraulic function Faulty pilot control valve (RCV). Do pilot control valve pressure test.
does not work. Inspect and repair valve.
Stuck open port relief valve. Replace relief valve.
Oil leaking past cylinder packings. Do boom and bucket cylinder leakage
test in group 3.
Blockage in oil lines or valve. Inspect lines for damage.
Disconnect and inspect lines for internal
blockage.
Loader control valve (MCV) spool stuck Inspect and repair valve.
in bore.
Low hydraulic power Leakage within work circuit. Do cylinder drift check in group 2.
Low system relief valve (main relief Do loader system and port relief valve
valve) setting. pressure test in group 3.
Low port relief valve setting. Do loader system and port relief valve
pressure test in group 3.

Leaking system relief valve. Remove and inspect valve.

Worn hydraulic pump. Do hydraulic pump performance check
in group 2.
Faulty pilot control valve (RCV). Do pilot control valve pressure test in
group 3.

6-47
 Problem Cause Remedy
Function drifts down Leaking cylinders. Do cylinder leakage checks in group 3.
Leaking seals in circuit relief valve (port Inspect seals. Replace relief valve.
relief valve) or valve stuck open.
Leaking loader control valve (MCV). Repair or replace valve section.
Boom drifts up Leakage in boom down spool. Remove and inspect boom down spool.
Boom down does not Safety valve not operated. Operate valve.
work (engine off)
Stuck pilot control valve. Inspect.
Faulty line filter. Remove and inspect filter.
Accumulation not operated. Inspect.
MCV spool stuck. Inspect and repair valve.
Oil overheats Low oil viscosity in hot weather. Use recommended oil.
Excessive load. Reduce load.
Holding hydraulic system over relief. Reduce load.
Leakage in work circuit. Do boom and bucket cylinder leakage
test in group 3.
Plugged fins in oil cooler. Inspect and clean oil cooler.
Internally plugged oil cooler. Do hydraulic oil cooler restriction test.
Incorrect system or circuit relief valve Do loader system and circuit relief valve
setting. pressure test in group 3.
Restriction in oil lines or loader control Inspect for dented or kinked lines.
valve (MCV).
Malfunctioning steering valve. Do hydraulic system restriction test in
group 3.
Leaking system main relief valve. Do hydraulic system restriction test in
group 3.
Remove and inspect valve and seals.
Worn hydraulic pump (internal leakage). Do hydraulic pump performance check
in group 2.
Function drops before Stuck open lift check valve. Do control valve lift check in group 2.
raising when valve is
activated

6-48
 Problem Cause Remedy
Hydraulic oil foams Low oil level. Add recommended oil.
Wrong oil. Change to recommended oil.
Water in oil. Change oil.
Loose or faulty suction lines (air leak in Tighten or install new lines.
system).
Remote control valve Leaking plunger seals. Remove, inspect and replace plunger
(RCV) leaking seals.

侍 Followings are general precautions for the hydraulic system and equipment.
1) Every structure has its limit of strength and durability. The relief valve is installed to limit the
pressure on the hydraulic equipment and protect various parts of the wheel loader from possible
damage. Therefore, never change the preset pressure of the relief valve unless absolutely
necessary.
2) Since the hydraulic equipment is built with precision, the presence of only the slightest amount of
dust and / or other particles in the hydraulic circuit might cause wear and/or damage, resulting in
unstable functions and/or damage, resulting in unstable functions and/or unexpected accidents.
Therefore, always keep hydraulic oil clean. Periodically, check the filter in the return circuit and
replace the element as necessary.
3) Extract about 200cc of hydraulic oil from the tank as a sample every 6 months. If possible, have it
analyzed by a specialist to confirm that the oil can still be used. Never extract the oil for sampling
until the oil temperature has become the normal operating temperature. Since the replacement
period varies depending on operating conditions, refer to Operator's Manual and change oil.
4) Should the equipment get damaged due to the presence of metal particles and/or foreign matter in
the circuit drain out the hydraulic oil and carry out flushing. Also, replace the filter element and
clean the hydraulic tank. Change the hydraulic oil entirely.
5) When checking the filter, if found metal particles in the element, drain out the hydraulic oil entirely,
flush the whole circuit, and then fill with new oil. The presence of metal particles may indicate
internal damage to the equipment. In such a case, check carefully before flushing, and repair or
replace as required.
6) To add and/or change the hydraulic oil, always use recommended oil. (Refer to the list of
recommended oils and lubricants at page 1-22, Recommended lubricants
lubricants..) Never mix oil of
different makes of kinds.
7) To change the hydraulic oil, use a clean vessel and funnel for pouring it into the tank. Never use
cloth because it might cause the presence of lint in the circuit.
8) When removing the hydraulic equipment, be sure to put plugs or caps on hoses, tube lines and
ports. Also, enter mating marks for later identification.

6-49
9) Disassemble and/or assemble the hydraulic equipment only in a clean place free of dust. When
disassembling, be careful about the interchangeability of parts, and clean the disassembled parts
with pure and clean mineral cleansing oil. Clean the internal passages as well. After the parts have
dried, wipe them off with a clean lint-free cloth.
10) When overhauling the hydraulic equipment replace all O-rings, backup rings, etc. with new ones.
Assemble O-rings with grease or vaseline applied.
11) After installing the equipment, add more hydraulic oil to make up for that lost during disassembly.
12) Tighten joints correctly. Loose joints will cause the hydraulic oil to leak. If the oil leaks, the tank oil
level drops and air gets sucked in, so the pump will break down. Also loose joints in suction lines
will take air in and might cause abnormal noise, malfunction or damage to pumps.

6-50
GROUP 3 TESTS AND ADJUSTMENTS

1. HYDRAULIC OIL CLEAN UP PROCEDURE USING PORTABLE FILTER CADDY

侍 Service equipment and tool
ÂPortable filter caddy
ÂTwo 4000 mm Ý 1in 100R1 Hoses
ÂQuick disconnect fittings.
ÂDischarge wand
ÂVarious size fittings.
侍 Brake system uses oil from hydraulic oil
tank. Flush all lines in the brake, pilot,
steering system and cut off system.
Disassemble and clean major
components for brake and steering
system. Remove and clean pilot caps
from main control valve.
Brake and steering components may fail
if brake and steering system is not
cleaned after hydraulic oil tank
contamination.
1) If hydraulic system is contaminated due to
a major component failure, remove and
disassemble steering cylinders to clean
debris from cylinders.
2) Install a new return filter element. Inspect
filter housing before installing new element.
侍 For a failure that creates a lot of debris,
remove access cover from hydraulic oil
tank. Drain and clean hydraulic oil tank
of fill the specified oil to hydraulic oil tank
through upper cover.
3) To minimize oil loss, pull a vacuum in
hydraulic oil tank using a vacuum pump.
Connect filter caddy suction line to drain
port at bottom of hydraulic oil tank using
connector. Check to be sure debris has
not closed drain port.
4) Put filter caddy discharge line into hydraulic
oil tank filler hole so end is as far away from
drain port as possible to obtain a thorough
cleaning of oil.

6-51
5) Start the filter caddy. Check to be sure oil
is flowing through the filters.
Operate filter caddy approximately 10
minutes so oil in hydraulic oil tank is
circulated through filter a minimum of four
times.
侍 Hydraulic oil tank capacity : 115˶(30.4
U.S. gal)
Leave filter caddy operation for the next
steps.
6) Start the engine and run it at high idle.
侍 For the most effective results, cleaning
procedure must start with the smallest
capacity circuit then proceed to the next
largest capacity circuit.
7) Operate all functions, one at a time,
through a complete cycle in the following
order: Clam, steering, bucket, and boom.
Also include all auxiliar y hydraulic
functions.
Repeat procedure until the total system
capacity has circulated through filter caddy
seven times, approximately 30 minutes.
Each function must go through a minimum
of three complete cycles for a through
cleaning for oil.
侍 Filtering time for machines with auxiliary
hydraulic functions must be increased
because system capacity is larger.
8) Stop the engine. Remove the filter caddy.
9) Install a new return filter element.
10) Check oil level in reservoir; Add oil if
necessary.

6-52
2. BOOM HEIGHT KICKOUT ADJUSTMENT
The bucket can be adjusted to a height
desired by using the boom kick-out device.
Park the machine on level ground and
bl o ck t h e t i r e s t o p r eve n t s u d d e n
movement of the machine.
Press the parking brake switch.
Fix the front and rear frames by using the
safety lock bar.
D o n o t wo r k u n d e r n e a t h t h e wo r k
equipment.

1) ADJUSTMENT OF THE BOOM KICKOUT AND

BUCKET LEVELER
(1) Lift kickout position
To set the lift kickout, raise the bucket to the
desired position above the midway point. Then Detent setting switch
push icon ( , A) for 2~3 seconds. The boom
will return to the programmed position when the
A
raise detent is activated and the boom is below
the kickout position. B

(2) Lower kickout position

(2)
To set the lower kickout, lower the bucket to the
Boom pivot pin
desired position below the midway point. Then Bucket pivot pin
push icon ( , A) for 2~3 seconds. The boom
will return to the programmed position when the
float detent is activated and the boom is at least
Midway
a foot above the kickout position. point

(3
(3)) Bucket leveler position
To set the bucket leveler, roll back the bucket to
the desired position. Then push icon ( , Detent position
B) for 2~3 seconds. The bucket will return to the Neutral
programmed position when the roll back detent
is activated and the bucket is below the leveler
position.

760F4OP28

6-53
3. TEST TOOLS
1) CLAMP-ON ELECTRONIC TACHOMETER
INSTALLATION
ÂService equipment and tools B
Tachometer
A : Clamp on tachometer.
Remove paint using emery cloth and C
connect to a straight section of injection
line within 100 mm (4 in) of pump.
D
Finger Tighten only-do not over tighten.
B : Black clip ( - ). Connect to main frame. A
C : Red clip (+). Connect to transducer.
75795SE32
D : Tachometer readout. Install cable.

2) DIGITAL THERMOMETER INSTALLATION

ÂService equipment and tools
Digital thermometer
A : Temperature probe.
Fasten to a bare metal line using a tie A
band. Wrap with shop towel. C
B : Cable. B
C : Digital thermometer.

75795SE33

3) DISPLAY MONITOR TACHOMETER

The display monitor tachometer is accurate
enough for test work.

7609A5SE35

6-54
4. HYDRAULIC OIL WARM UP PROCEDURE
1) Install temperature reader (see temperature
reader installation procedure in this group).
2) Run engine at high idle.
3) Hold a hydraulic function over relief to heat
the oil.
4) Periodically cycle all hydraulic functions to
distribute warm oil.
5) Heat oil to test specification (approx. 45˚C).

侍 Ride control system (option)

Attention
1) Before carrying out any maintenance work B
the accumulators must be unloaded (zero A
pressure).
2) For this, loosen the nut (A) and bolt (B)
counterclockwise with 10 mm spanner.
侍 The accumulator will be unloaded (zero
pressure) in less than a minute.
3) The lifting system must firstly be secured
against lowering.
4) After carrying out maintenance work, screw
the bolt (B) and nut (A). Ride control valve
ÂTightening torque
A : 2.04 kgfÂm (14.8 lbfÂft) 7609A6WE28

6-55
5. MAIN HYDRAULIC PUMP FLOW TEST
 SPECIFICATION
Oil temperature 45Ü5˚C (113Ü9˚F)
Engine speed 2130Ü25 rpm
T
Test pressure 200Ü5 bar (2900 psi) P

Maximum pump flow 249˶/min (65.8 gpm)

 FLOW METER GAUGE AND TOOL
Flow meter
Gauge 0~35 MPa (0~350 bar, 0~5000 psi)
Temperature reader
1) Make test connections. MCV
2) Install temperature reader.
(see temperature reader installation
procedure in this group)
3) Heat hydraulic oil to specifications.
(see hydraulic oil warm up procedure in this Hyd
tank
group) Main pump
4) Run engine at test specifications.
5) Close flow meter loading valve to increase
pressure to test specifications.
6) Read flow meter.
7) If flow is below specifications, check suction
line and suction pressure for abnormality
before removing pump. 760F6WE29

6-56
6. L
LOOADER SYSTEM AND PORT RELIEF
VALVE PRESSURE TEST
 SPECIFICATION
Oil temperature (40~50˚C)
Relief valve Engine speed Relief pressure
System (M) 280Ü5 kg/cm2
High
LS relief valve (3980Ü70 psi)
Boom 340Ü10 kg/cm2 U
Low
raise (U) (4840Ü140 psi)
M
Boom 340Ü10 kg/cm2
Low
down (W) (4840Ü140 psi)
LS relief valve
Bucket 340Ü10 kg/cm2 W
Low
rollback (R) (4840Ü140 psi)
Bucket P
300Ü10 kg/cm2
Low D T
dump (D) (4270Ü140 psi)

 Gauge and tool R

Gauge 0~35 MPa (0~350 bar, 0~5000 psi)
M : System (main) relief valve
R : Bucket rollback relief
D : Bucket dump relief
U : Boom raise relief Pressure measure
positon : MCV P port
1) Install fitting and pressure gauge to test
port in pump delivery line.
2) Install temperature reader. P

(see temperature reader installation

procedure in this group)
3) Heat hydraulic oil to specifications.
(see hydraulic oil warm up procedure in this MCV
group)
4) To check the system relief (M), run engine
Hyd tank
at high idle.
Main pump
Lower boom to bottomed position.
Slowly activate boom down function while
watching pressure gauge. If pressure is not
to specification, loosen lock nut on system
relief valve (M) and adjust to specification.
侍 Do not adjust the system relief valve
above 280 kg/cm2 (3980 psi).
Damage to the pump will result from
excessive pressure settings.
760F6WE28

6-57
7. HYDRAULIC SYSTEM RESTRICTION TEST
 SPECIFICATION
Oil temperature 45Ü5˚C (113Ü9˚F)
Engine speed High idle
Maximum pressure 4.5 MPa (45 bar, 640 psi) at
steering valve (EHPS).
Maximum pressure at main control valve
1 MPa (10 bar, 145 psi)
 GAUGE AND TOOL
Gauge 0~7 MPa (0~70 bar, 0~1000 psi) 2EA
This test will check for restrictions in the hydraulic
system which can cause overheating of hydraulic P
oil.
1) Install temperature reader.
(see temperature reader installation procedure in
this group) Steering valve(EHPS)

2) Heat hydraulic oil to specifications.

(see hydraulic oil warm up procedure in this
group)
3) Connect fitting and gauge to steering valve.
4) Connect fitting and gauge to main control valve.
Do not operate steering or loader funct-ions
or test gauge may be damaged.
T
5) Run engine at specification and read pressure
gauges.
If pressure is more than specification at the
loader control valve, check for a kinked, dented
or obstructed hydraulic line. Check loader control MCV
valve for a binding spool.
If pressure is more than specification at the
steering unit, inspect neutral condition of the Hyd tank
steering unit and steering valve for a stuck spool. Main pump
Make sure orifice plugs are installed in ends of
priority valve spool.
Check for plugged orifice in priority valve and
760F6WE39
dynamic signal orifice on steering valve body.

6-58
8. LOADER CYLINDER DRIFT TEST
 SPECIFICATION
Oil temperature 45Ü5˚C (113Ü9˚F)
Boom horizontal
Bucket horizontal
Bucket unloaded
Item Standard value
Retraction of boom
15 mm
cylinder rod B
Retraction of bucket
24 mm
cylinder rod

 GAUGE AND TOOL

A
Stop watch
Temperature reader
A : Retraction of boom cylinder rod
Put the pilot cut off switch in the OFF
B : Retraction of bucket cylinder rod
position.
Do not go under the work equipment.
1) Set the boom and bucket horizontal, then
stop the engine.
2) Stop the engine, wait for 5 minutes, then
start measuring.
3) Measure the amount the boom and bucket
cylinder rods retract during 15 minutes. 7577AWE31

6-59
9. BOOM AND BUCKET CYLINDER LEAKAGE TEST
余 SPECIFICATION
Oil temperature 45Ü5˚C (113Ü9˚F)
Engine speed Low idle
Maximum leakage 15 m˶/min (1/2 oz/min)
余 GAUGE AND TOOL
Temperature reader
Stop watch
Measuring container
1) Fasten temperature sensor to head end
port of cylinder to be tested. Cover sensor
with a shop towel.
2) Heat hydraulic oil to specifications (see
hydraulic oil warm up procedure in this
group).
Never work under raised equipment
unless it is supported with a hoist or
support stands.
3) Full extend the cylinder to be tested. If
testing the boom cylinders, restrain boom in
the fully raised position using a hoist or a
stand.
侍 Check cylinders for leakage in the fully
extended position only. In the retracted
position contacts the end of the cylinder
and seals off piston seal leakage.
4) Remove and plug cylinder rod end hose or
line.
5) Run engine at slow idle. Activate control
lever to extend cylinder for 1 minute over
relief while measuring leakage for open
port.
If leakage is within specification, excessive
cylinder drift is caused by leakage in the
(770-3ATM) 6-56
loader control valve or circuit relief valve.

6-60
10. PILOT CONTROL VALVE (EH CONTROL BLOCK) PRESSURE
PRESSURE TEST
 SPECIFICATION
Oil temperature 45Ü5˚C (113Ü9˚F)
Engine speed High idle
Minimum pressure 30 bar EH control block
Pressure range 35~50 bar

 GAUGE AND TOOL

P
Gauge 0~7 MPa (0~70 bar, 0~1000 psi)
1) Lower boom to ground.
2) Connect gauge to the pilot pressure port of
function to be checked.
3) Install temperature reader (see temperature
reader installation procedure in this group).
4) Heat hydraulic oil to specification (see
hydraulic oil warm up procedure in this
group).

Safety valve

760F6WE38

6-61
11. CYCLE TIME TEST
 SPECIFICATION
Oil temperature 45Ü5˚C (113Ü9˚F)
Engine speed High idle
Function Operating conditions Maximum cycle time (seconds)
Boom raise Bucket flat on ground to full height 5.8
Boom lower (float) Full height to ground level 3.1
Bucket dump Boom at full height 1.4
Bucket rollback Boom at full height 1.8
Steering (No. of turns) Frame stop to stop 3.8 turns

Hydraulic pump performance cycle time.

Function Operating conditions Maximum cycle time (seconds)
Bucket flat on ground to full height
Boom raise 10
while holding steering over relief

6-62
12. HYDRAULIC OIL FILTER INSPECTION
PROCEDURE
1) Lower the bucket to the ground, stop the
engine, move the control lever back and
forth several times, and clean all over the
upper surface of the hydraulic oil tank.
2) Remove the bolts and take out the filter
case cover and O-ring.
Cover
3) Remove the spring and bypass valve. O-ring
4) Remove the filter element from the tank. Spring
By-pass valve
5) Check the element and the filter case
bottom for debris. Excessive amounts of
brass and steel particles can indicate a Return filter
failed hydraulic pump or a pump failure in
process. A rubber type of material can
indicated cylinder packing or other packing
failure.
ö The hydraulic oil filter in the filter case of
the hydraulic oil tank should be replaced
every 1000 operating hours or more often.
When the filter element is replaced,
please keep as follows.
(1) Clean the inside of the filter case.
(2) Place new element in the proper positions
inside the filter case.
(3) Install the bypass valve and spring.
Make sure the element stand upright, and
check for complete contact of the element
bottom with the filter case bottom.
(4) Install the O-ring and filter case covers.
Tighten them with bolt. Replace the
9656WE24
O-ring with new one if damaged.

6-63
GROUP 4 DISASSEMBLY AND ASSEMBLY

1. MAIN PUMP
1) STEERING (1/2)
10
24

27
23

6,31

37

2 16
12
51
53
33 52
1-2
54

30 1-1

7
17
22

15
20
25 76096WE11

1 Rotary group 12 Adjustment shim 27 Socket screw

1-1 High speed rotary group 15 Taper roller bearing 30 Locking screw
1-2 Control plate 16 Taper roller bearing 31 Double break-off pin
2 Adjusting piece 17 Bearing liner 33 Cylinder pin
5 Pump housing 20 Shaft seal ring 37 Side mark ring
6 Port plate 22 O-ring 51 Control valve
7 Swash plate 23 O-ring 52 Gasket
8 Drive shaft 24 O-ring 53 Socket head screw
10 Splined hub 25 Retaining ring 54 Locking screw

6-64
 LOADER (2/2)

28

27
23

6,31
2
2

41
11
43 16
33 42 12

44 1-2

1-1
30

7
17
22

8
15
20
25
76096WE12

1 Rotary group 12 Adjustment shim 28 Locking screw

1-1 High speed rotary group 15 Taper roller bearing 30 Locking screw
1-2 Control plate 16 Taper roller bearing 31 Double break-off pin
2 Adjusting piece 17 Bearing liner 33 Cylinder pin
5 Pump housing 18 Shaft seal ring 41 Control valve
6 Port plate 22 O-ring 42 Gasket
7 Swash plate 23 O-ring 43 Socket screw
8 Drive shaft 25 Retaining ring 44 Locking screw
11 Adjustment shim 27 Socket screw

6-65
2) GENERAL REPAIR GUIDELINES
ö Observe the following guidelines when
carrying out repairs on hydraulic pumps.
(1) Close off all openings of the hydraulic unit.
(2) Replace all of the seals.
Use only original spare parts.
(3) Check all sealing and sliding surfaces for
wear.
ö Re-work of the sliding surfaces by using,
for example abrasive paper, can damage
the surface.
(4) Fill the hydraulic pump with hydraulic oil
before commissioning.

3) SEALING THE DRIVE SHAFT

(1) Protect the drive shaft. 1
Remove the circlip.
Remove the shaft seal.
1 Circlip 2 Shaft seal

2
75796WE60

(2) Change the shaft seal and check its

sliding surface (drive shaft) and housing,
grease the sealing ring.

75796WE58

(3) Assemble the sealing ring, fitting tool

holds the correct position of the sealing
ring in the pump housing.
Assemble the circlip in the correct
position.

75796WE59

6-66
4) SEALING / CLEANING THE CONTROL
A
VALVE
(1) Disassemble the control valve.
ö Measure dimension A and note down.
Check sealing surface (1).
A

75796WE62

5) DISASSEMBLE THE PUMP

(1) Remove the control valve.

75796WE63

(2) Mark the location of the connection plate

on the housing.

75796WE64

6-67
(3) Remove the connection plate fixing bolts
and the connection plate.
ö Distributor plate and adjustment piston
can drop down.

75796WE65

(4) Remove distributor plate.

Take note of the orientation.
ö Remove bearing with withdrawal tool.
Do not damage the sealing surface.

75796WE66

(5) Remove the rotary group in a horizontal

position.

75796WE67

6-68
(6) Remove swash plate and bearing shells.

75796WE68

(7) Remove the circlip and the shaft seal.

75796WE69

(8) Remove the drive shaft through rear side.

75796WE70

(9) Pre-tension the spring (1) using a suitable

1
device. 2
Remove circlip (2).
Remove spring (1) and pressure pins (3).

3 75796WE72

6-69
(10) Use bearing puller to remove outer
bearing race of front bearing out of
housing press seat.

75796WE74

(11) Remove the control plate.

75796WE75

(12) Use bearing puller to remove outer

bearing race of rear bearing - press seat.

75796WE76

(13) Disassemble the guide of control piston

(Mounting position: pilot valve side).

75796WE77

6-70
(14) Disassemble the guide of the opposite
piston.

75796WE78

6) INSPECT HINTS
(1) Renew all bearings.

75796WE79

(2) Check :
1 Wear on splines, rust 1
6
5
2 Drive shaft seal wear grooves
4
3 Bearing seat
2 3
4 Splines for cylinder drive 1
5 Bearing seat

75796WE80

(3) Check :
Sliding surface free of grooves.

75796WE81

6-71
(4) Check :
Bearing surfaces.

75796WE82

(5) Check :
That the retaining plate is free of grooves
and that there is no wear in the slipper
pad area.

75796WE83

(6) Check :
Check to see that there are no scratches 1
or metal deposits on the sliding surface
(1) and that there is no axial play (2)
(Pistons must only be replaced as a set).

2
2

75796WE84

(7) Check :
1 Cylinder bores 2 1
2 Splines

75796WE85

6-72
(8) Free of grooves, no signs of wear.

75796WE86

(9) Check :
Cylinder sliding surface free of grooves,
no wear, no embedded foreign particles.
That there are no scratches on the control
plate. (Only replace them as a set).

75796WE87

(10) Check : L1
Mounting surface - control plate
undamaged.

75796WE88

(11) Check :
Check running conditions of the control
piston.

75796WE89

6-73
(12) Check :
Check running conditions of the opposite
piston.

75796WE90

7) ADJUSTMENT OF TAPER ROLLER 0~0.05mm

BEARING SET
(1) Cast iron housing must have initial
tension of the bearings: 0~0,05 mm, grind
position A if necessary.

Position A

75796WE91

8) PUMP ASSEMBLY
(1) Fit the seal into the housing.
Fit the circlip.

75796WE92

(2) Fit the drive with bearing from rear end.

ö Do not touch seal lip with edge of keyway
or spline.

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(3) Fit pressure pins using an assembly aid.

75796WE94

(4) Pre-tension the spring using a suitable

device.

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(5) Assemble piston with retaining plate.

ö Oil piston and slipper pad.

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(6) Fit rotary group.
ö Hold the piston by using an O-ring.
Fit O-ring (1).

75796WE98

(7) Fit bearing (1) in connection plate.

Fit cyilindrical pin (2).
Fit O-rings (3) 4 pieces.
5
Fit adjustment spool (4) and guide piston
(4a).
Fit distributor plate (5) (direction of
rotation dependent)
ö Assembly. 4
1
Hold the components in place with
grease. 2
3
4a

75796WE99

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(8) Fit distributor plate.
ö Assembly aid : Grease

75796WE100

(9) For clockwise rotation pumps the

distributor plate is off-set by 4˚ to the right
from the centre position.
(Clockwise and anti-clockwise rotation
distributor plates are not identical).

75796WE101

(10) Fit connection plate and control valve.

75796WE63

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2. MAIN CONTROL VALVE
1) STRUCTURE (1/2)

61

62

60

36 38
38
37
79

35
50

79
74
33
31

33 32
79

30

86
102 71

84
74

11
79
85
165
76096WE13

11 Housing 37 O-ring 74 Compensator valve

30 O-ring 38 O-ring 79 Pressure valve
31 O-ring 50 Housing 84 Flow regulator
32 O-ring 60 Plate 85 Precharge valve
33 O-ring 61 Cylinder screw 86 Pilot oil supply
35 O-ring 62 Washer 102 Locking screw
36 O-ring 71 Shuttle valve 165 Pressure relief valve

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 STRUCTURE (2/2)

23
21
91
12
90 96
96
12 90 20
21 91
23 39

23
50 21
20
39 13

95
40 91 19
90
90 91
96 34 23
12
21
23
20
20
12
34
96
34 90
40
91
41 34

91
90 11
96

21
23

12

20

76096WE14

11 Housing 21 Throttle check valve 50 Housing

12 Cover 23 Threaded steel pipe fitting 90 Compression spring
13 Cover 34 O-ring 91 Spring retainer
14 Cover 39 O-ring 95 Spring retainer
19 Bolt 40 Spool 96 Spring retainer
20 Bolt 41 Spool

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2) GENERAL PRECAUTIONS
(1) Clean room with no dust is recommended for maintenance. Because hydraulic components
are precision, and have minute clearance. Tool and wash-oil must be clean, too. Handle
them carefully.
(2) At removing control valve from the machine, wash around the piping port, and neither dust
nor water should go into inside with plugging. It is same at attaching the machine.
(3) Prepare the required parts by checking structure figure before assembly. There are parts
which are supplied with only sub-assembly part, so check the parts list before assembly.
3) PRECAUTIONS FOR DISASSEMBLY
(1) Handle the components carefully not to drop them or bump them with each other as they are
made with precision.
(2) Do not force the work by hitting or twisting as burred or damaged component may not be
assembled or result in oil leakage or low performance.
(3) When disassembled, tag the components for identification so that they can be reassembled
correctly.
(4) Once disassembled, O-ring and back-up rings are usually not to be used again.(Remove them
using a wire with its end made like a shoe-horn. Be careful not to damage the slot)
(5) If the components are left disassembled or half-disassembled, they may get rust from moisture or
dust. If the work has to be interrupted, take care to prevent rust and dust.
4) PRECAUTIONS FOR REASSEMBLY
(1) Take the same precautions as for disassembly.
(2) When assembling the components, remove any metal chips or foreign objects and check them
for any burrs or dents. Remove burrs and dents with oil-stone, if any.
(3) O-rings and back-up rings are to be replaced with new ones, as a rule.
(4) When installing O-rings and back-up rings, be careful not to damage them.
(Apply a little amount of grease for smoothness)
(5) Tighten the bolts and caps with specified torque.

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5) DISASSEMBLY AND ASSEMBLY
(1) Spool
Η Loosen the bolt (2EA).
ÂTool : Wrench 5 mm
ÂTightening torque : 0.85 kgfÂm
(6.1 lbfÂft)

76096WE40

Θ Remove the cover, spring retainer, spring

and spool.

76096WE41

1 Spring
1
2 Spring ratainer
3 Spool
4 Cover
5 Bolt
2 3 4 5

76096WE42

(2) Compensator valve

ÂTool : Spanner 42 mm

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 ÂTightening torque : 20.4 kgfÂm
(148 lbfÂft)

76096WE44

(3) Port relief valve

ÂTool : Spanner 30 mm

76096WE45

ÂTightening torque : 10.2 kgfÂm

(73.8 lbfÂft)

76096WE46

(4) Precharge valve

ÂTool : Spanner 32 mm

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 ÂTightening torque : 6.1 kgfÂm
(44.3 lbfÂft)

76096WE48

(5) Shttle valve

ÂTool : Spanner 22 mm

76096WE49

ÂTightening torque : 3.6 kgfÂm

(25.8 lbfÂft)

76096WE50

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