GROUP 4 MAIN CONTROL VALVE

1. REMOVAL AND INSTALL

1) REMOVAL
(1) Lower the work equipment to the ground
and stop the engine.
(2) Operate the control levers and pedals
several times to release the remaining
pressure in the hydraulic piping.
(3) Loosen the breather slowly to release the 13031GE18

pressure inside the hydraulic tank.

Escaping fluid under pressure can
penetrate the skin causing serious
injury.
ö When pipes and hoses are disconnected,
the oil inside the piping will flow out, so
catch it in oil pan.
(4) Remove bolts and disconnect pipe.
(5) Disconnect pilot line hoses.
(6) Disconnect pilot piping. 1408DA10

(7) Sling the control valve assembly and

remove the control valve mounting bolt.
ÂWeight : 80k (180lb)
(8) Remove the control valve assembly.
When removing the control valve
assembly, check that all the piping have
been disconnected.
2) INSTALL
(1) Carry out installation in the reverse order
to removal.
1408DA11
(2) Bleed the air from below items.
Η Cylinder (Boom, arm, bucket)
Θ Swing motor
Ι Travel motor
ö See each item removal and install.

(3) Confirm the hydraulic oil level and recheck

the hydraulic oil leak or not.

1408DA12

8-29
2. STRUCTURE(1/4)
91
30

71
16
82
28, 29
91 90 73
43

42 78
90
16 45
41
90
40
5 46

67 7
10 31
85
12
65 69
68
14
64 77
87
76
66 39 87
77
68 84 79
62
38 89
63 37 44
36
52 35 79
53
75 33 47
54
1 34

DETAIL OF LOCK VALVE

90 1607A8MC04
63
15 53 Spring
62 49
90 54 Plug
48
66 51 91 57 Plug
57 62 Poppet
76
64 63 Filter
32 64 Spring seat
65
69 65 Spring
85 66 Piston
50 35 Restrictor 67 Socket
74 36 Spring 68 Plug
67
37 Poppet guide 69 Plug
1 Housing-P1 38 Pilot poppet 71 Plug
5 Spool assy 39 Poppet seat 73 Plug
7 Spool assy 40 Piston 1 74 Socket head bolt
10 Spool assy 41 Piston guide 75 O-ring
12 Spool assy 42 Spring 1 76 O-ring
14 Spool assy 43 Piston 2 77 O-ring
15 Pilot cover A 44 Sleeve 78 O-ring
16 Pilot cover B1 45 Spool 79 O-ring
28 Lock valve kit A 46 Spring 2 82 O-ring
29 Lock valve kit B 47 Stopper 84 O-ring
30 Socket head bolt 48 Regeneration selector spool 85 O-ring
31 Holding block 49 Spring 87 Back up ring
32 Regeneration block 50 Stopper 89 Back up ring
33 C-ring 51 Piston 90 O-ring
34 Poppet 52 Poppet 91 Socket head bolt

8-30
STRUCTURE(2/4)

24

25

72
80

19
20
84
80 18
72
80 84
76 72 18
86 22
78 23
88 81
81 21
61 80
68
72
76
86 19
78 20
88
81 25 84
27 18
59

25

1607A8MC05

18 Plug 25 Overload relief valve 78 O-ring

19 Poppet 1 27 Plug 80 O-ring
20 Spring 59 Plug 81 O-ring
21 Plug 61 Plug 84 O-ring
22 Poppet 2 68 Plug 86 Back-up ring
23 Spring 72 Plug 88 Back-up ring
24 Main relief valve 76 O-ring

8-31
STRUCTURE(3/4)
73
91 78
91
30

16 71
16
28,29 82
90 90
91 43 73

42 78
91
91 16 45
90
41
90 17 3
4 40
16
46
90 6
90

11
9 31

13 69

92 72 77
80 87 76
39 87
77
84 79
89
38
2 37 44
36
80 79
35
72 47
90 33
81 34
21 15

76 DETAIL OF LOCK VALVE

91
8186 78
60 1607A8MC06
90 73
15
8

91
90 47 Stopper
60 Plug
17
69 Plug
71 Plug
91 72 Plug
2 Housing-P2 31 Holding block 73 Plug
3 Spool assy 34 Poppet 74 Socket head bolt
4 Spool assy 35 Restrictor 76 O-ring
6 Spool assy 36 Spring 77 O-ring
8 Spool assy 37 Poppet guide 78 O-ring
9 Spool assy 38 Pilot poppet 79 O-ring
11 Spool assy 39 Poppet seat 80 O-ring
13 Spool assy 40 Piston 1 81 O-ring
15 Pilot cover A 41 Piston guide 82 O-ring
16 Pilot cover B1 42 Spring 1 87 Back up ring
17 Lock valve kit B2 43 Piston 2 89 Back up ring
21 Plug 44 Sleeve 90 O-ring
28 Lock valve kit A 45 Spool 91 Socket head bolt
29 Lock valve kit B 46 Spring 2 92 Spool assy

8-32
STRUCTURE(4/4)

18
84
20
21 19 58
81
82
77 25
70 87 26
83 72 56
80 55
26
59
81
77
87
72
80 21
81
23
22
18
84 21
20 81
19

21
81
70
83

26

25

26

1607A8MC07

18 Plug 26 Plug 77 O-ring

19 Poppet 1 55 Orifice 80 O-ring
20 Spring 56 Coin type filter 81 O-ring
21 Plug 58 Plug 82 O-ring
22 Poppet 2 59 Plug 83 O-ring
23 Spring 70 Plug 84 O-ring
25 Overload relief valve 72 Plug 87 Back-up ring

8-33
3. DISASSEMBLY AND ASSEMBLY
1) GENERAL PRECAUTIONS
(1) All hydraulic components are manufactured to a high precision. Consequently, before
disassembling and assembling them, it is essential to select an especially clean place.
(2) In handling a control valve, pay full attention to prevent dust, sand, etc. from entering into it.
(3) When a control valve is to be remove from the machine, apply caps and masking seals to all
ports. Before disassembling the valve, recheck that these caps and masking seals are fitted
completely, and then clean the outside of the assembly. Use a proper bench for working. Spread
paper or a rubber mat on the bench, and disassemble the valve on it.
(4) Support the body section carefully when carrying or transferring the control valve. Do not lift by
the exposed spool, end cover section etc.
(5) After disassembling and assembling of the component it is desired to carry out various tests(For
the relief characteristics, leakage, flow resistance, etc.), but hydraulic test equipment is necessary
for these tests. Therefore, even when its disassembling can be carried out technically, do not
disassemble such components that cannot be tested, adjusted, and so on. Additionally one
should always prepare clean cleaning oil, hydraulic oil, grease, etc. beforehand.
2) TOOLS
Before disassembling the control valve, prepare the following tools beforehand.

Name of tool Quantity Size(mm)

Vice mounted on bench(Soft jaws) 1 unit
Hexagon wrench Each 1 piece 5, 6, 10, 12 and 14
Socket wrench Each 1 piece 27 and 32
Spanner Each 1 piece 32(Main relief valve)

8-34
3) DISASSEMBLY
(1) Disassembly of spools without holding valve
Η Loosen hexagon socket head bolts with washer
(Hexagon wrench : 5mm)
Θ Remove the pilot cover.
ö Pay attention not to lose the O-ring under the pilot cover.
Ι Remove the spool assembly from the body by hand slightly.
ö When extracting each spool from its body, pay attention not to damage the body.
ö When extracting each spool assembly, it must be extracted from spring side only.
ö When any abnormal parts are found, replace it with completely new spool assembly.
ö When disassembled, tag the components for identification so that they can be reassembled
correctly.

Return spring

Pilot cover

Socket head bolt

O-ring 1607A8MC10

8-35
(2) Disassembly of spools with holding valve(Boom 1, Arm 1 spool)
Η Loosen hexagon socket head bolts with washer
(Hexagon wrench : 5mm)
Θ Remove the pilot cover with internal parts.
ö Pay attention not to lose the O-ring and the poppet under the pilot cover.
ö Pay attention not to damage the "piston A" under pilot cover.
Ι Remove the spool assembly from the body by hand slightly.
ö When extracting each spool from its body, pay attention not to damage the body.
ö When extracting each spool assembly, it must be extracted from spring side only.
ö When any abnormal parts are found, replace it with completely new spool assembly.
ö When disassembled, tag the components for identification so that they can be reassembled
correctly.

Boom 1 spool

Pilot cover

Socket head bolt

O-ring

Poppet seat
Poppet Piston A

1607A8MC11

8-36
(3) Disassembly of the holding valve
Η Remove the pilot cover with the holding valve as described on previous page.
ö Do not disassembled internal parts of the pilot cover.
Θ Loosen the poppet seat and remove the poppet, the spring seat, the spring and the check.
(Spanner : 26 mm)
ö Pay attention not to lose the poppet.
ö Do not disassembled internal parts of the check.

Boom 1 spool

Pilot cover

Socket head bolt

Spring Poppet Poppet seat

Check Spring seat

1607A8MC12

8-37
(4) Disassembly of the load check valve and the negative relief valve
Η The load check valve
a. Fix the body to suitable work bench.
ö Pay attention not to damage the body.
b. Loosen the plug (Hexagon wrench : 10mm).
c. Remove the spring and the load check valve with pincers or magnet.
Θ The negative relief valve
a. Loosen the socket (Hexagon wrench : 12mm).
b. Remove the spring, the spring holder, the piston and the negative control poppet.

Plug
Spring

Load check valve

Coin type filter Spring holder

Negative Piston Spring Socket

control
poppet

1607A8MC13

8-38
(5) Disassembly of the main and overload relief valve
Η Fix the body to suitable work bench.
Θ Remove the main relief valve.
(Spanner : 32mm)
Ι Remove the overload relief valve.
(Spanner : 32mm)
ö When disassembled, tag the relief valve for identification so that they can be reassembled
correctly.
ö Pay attention not to damage seat face.
ö When any abnormal parts are found, replace it with completely new relief valve assembly.

32mm HEX

Main relief valve

32mm HEX

Overload relief valve 1607A8MC14

8-39
(6) Inspection after disassembly
Clean all disassembled parts with clean mineral oil fully, and dry them with compressed air.
Then, place them on clean papers or cloths for inspection.
Η Control valve
a. Check whole surfaces of all parts for burrs, scratches, notches and other defects.
b. Confirm that seal groove faces of body and block are smooth and free of dust, dent, rust etc.
c. Correct dents and damages and check seat faces within the body, if any, by lapping.
ö Pay careful attention not to leave any lapping agent within the body.
d. Confirm that all sliding and fitting parts can be moved manually and that all grooves and path's
are free foreign matter.
e. If any spring is broken or deformed, replace it with new one.
f. When a relief valve does not function properly, repair it, following it's the prescribed disassembly
and assembly procedures.
g. Replace all seals and O-rings with new ones.
Θ Relief valve
a. Confirm that all seat faces at ends of all poppets and seats are free of defects and show uniform
and consistent contact faces.
b. Confirm manually that main poppet and seat can slide lightly and smoothly.
c. Confirm that outside face of main poppet and inside face of seat are free from scratches and so
on.
d. Confirm that springs are free from breakage, deformation, and wear.
e. Confirm that orifices of main poppet and seat section are not clogged with foreign matter.
f. Replace all O-rings with new ones.
g. When any light damage is found in above inspections, correct it by lapping.
h. When any abnormal part is found, replace it with a completely new relief valve assembly.

8-40
4) ASSEMBLY
(1) General precaution
Η In this assembly section, explanation only is shown.
For further understanding, please refer to the figures shown in the previous structure &
disassembly section.
Θ Pay close attention to keeping all seals free from handling damage and inspect carefully for
damage before using them.
Ι Apply clean grease or hydraulic oil to the seal so as to ensure it is fully lubricated before
assembly.
Κ Do not stretch seals so much as to deform them permanently.
Λ In fitting O-rings, pay close attention not to roll them into their final position in addition, a twisted
O-ring cannot easily untwist itself naturally and could thereby cause inadequate sealing and
thereby both internal and external oil leakage.
Μ Tighten fitting bolts for all sections with a torque wrench adjusted to the respective tightening
torque.
Ν Do not reuse removed O-rings and seals.
(2) Load check valve
Η Assemble the load check valve and spring.
Θ Put O-rings on to plug.
Ι Tighten plug to the specified torque.
ÂHexagon wrench : 10mm
ÂTightening torque : 6~7kgfÂm(43.4~50.6lbfÂft)
(3) Negative control relief valve
Η Assemble the nega-con poppet, piston, spring holder and spring together into body.
Θ Put O-ring on to plug and tighten the latter to its specified torque.
ÂHexagon wrench : 12mm
ÂTightening torque : 8~9kgfÂm(57.8~65.1lbfÂft)
(4) Main relief, port relief valves
Install main relief valve, overload relief valve into the body and tighten to the specified torque.
Tightening torque
Component Tools
kgfÂm lbfÂft
Main relief valve Spanner 32mm 8~9 57.8~65.1
Overload relief valve Spanner 32mm 8~9 57.8~65.1

(5) Main spools

Η Carefully insert the previously assembled spool assemblies into their respective bores within of
body.
ö Fit spool assemblies into body carefully and slowly. Do not under any circumstances push them
forcibly in.

8-41
(6) Covers
Η Fit spool covers to the non-spring assembly end of the spool, and tighten the hexagonal socket
head bolts to the specified torque.
ÂHexagon wrench : 5mm
ÂTightening torque : 1.0~1.1kgfÂm(7.2~7.9lbfÂft)
ö Confirm that O-rings have been fitted.
Θ Fit spring covers to the spring end for the spools, and tighten hexagon socket head bolts to the
specified torque.
ÂHexagon wrench : 5mm
ÂTightening torque : 1.0~1.1kgfÂm(7.2~7.9lbfÂft)
ö Confirm that O-rings have been fitted.
(7) Holding valves
Η Assemble the check, spring seat and poppet together into body.
Θ Tighten the poppet seat to the specified torque.
ÂSpanner : 26mm
ÂTightening torque : 6~7kgfÂm(43.4~50.6lbfÂft)
Ι Fit the "piston A" under pilot cover with internal parts into hole on the poppet seat.
Κ Tighten hexagon socket head bolt to specified torque.
ÂHexagon wrench : 5mm
ÂTightening torque : 1.0~1.1kgfÂm(7.2~7.9lbfÂft)

8-42