VOLVO CONSTRUCTION EQUIPMENT

Service manual
EC210D

CONTENTS
9 Hydraulic system,
working hydraulics and
other equipment
9:2 Main control valve
 Foreword
This booklet is part of a complete service manual. Read the
foreword in the service manual.

NOTICE
In a link or cross-reference to a specification the number
stated in the link refers to respective section in the booklet
'0 General', e.g. 311 Battery, specification.

WARNING
Always read the booklet Safety before proceeding.

PUB 20048403-A 2015.10

1
Table of contents
91 WORKING HYDRAULICS; SERVO HYDRAULICS
912 Working hydraulics
9121 Directional valve; control valve
Hydraulic circuits, ports ............................................................................... 5
Main control valve, description ................................................................... 6
Main control valve, sectional view ............................................................ 9
Pressure relief valve, troubleshooting ....................................................... 12
Main control valve troubleshooting ........................................................... 12
General, precautions ................................................................................ 15
Removal, precautions ............................................................................. 15
Disassembly, precautions ....................................................................... 15
Assembly, precautions ............................................................................ 15
General, inspection ................................................................................. 15
General, tools ........................................................................................... 16
Holder (Material: Brass) .......................................................................... 17
Main spool, disassembly and assembly ................................................... 17
Main relief valve, description .................................................................... 19
Pressurized (350 kgf/cm2) ...................................................................... 20
Main relief valve, adjustment .................................................................... 20
Adjustment of the limiting pressure ......................................................... 20
Measurement .......................................................................................... 20
Hydraulic pressure .................................................................................. 20
High pressure adjustment (Boost pressure) ........................................... 21
Low pressure Adjustment (Standard pressure) ...................................... 22
Main relief valve, disassembly and assembly ........................................... 22
Main pressure relief valve, replacing ........................................................ 23
Port relief valve, description ...................................................................... 24
Overload operation ................................................................................. 24
Anti–cavitation operation ......................................................................... 25
Port relief valve pressure, measuring and adjusting ................................. 26
Measuring condition ................................................................................ 26
Measurement .......................................................................................... 26
Hydraulic pressure .................................................................................. 26
Primary pump supply to each actuator and test port location. ................ 26
Pressure measuring port of track motor ................................................. 27
Pressure measuring port of slew motor .................................................. 27
Adjustment of the pump displacement .................................................... 27
Port relief valve pressure, adjustment .................................................... 28
Slew motor port relief valve pressure, adjustment .................................. 29
Port relief valve pressure, adjustment (When installing or
dismantling the line rupture valve ........................................................... 29
Port relief valve, disassembly ................................................................... 29
Boom holding valve, description ............................................................... 31
Spool in neutral ....................................................................................... 31
Spool operating ....................................................................................... 31
Boom holding valve, disassembly ............................................................. 33
Boom regenerating valve, description ...................................................... 35
Boom back pressure check valve, disassembly and assembly ................ 36
Arm holding valve, description .................................................................. 36
Spool in neutral ....................................................................................... 36
Spool operating ....................................................................................... 37
Arm holding valve, disassembly and assembly ........................................ 38
Arm regenerating valve, description ......................................................... 39
Pressure on rod side is high [PB > PA ] .................................................. 40
Pressure on piston is high [PA > PB ] ..................................................... 41
Arm regenerating and arm conflux check valve, disassembly and
assembly ................................................................................................... 41

3
 Arm parallel conflux valve, disassembly and assembly ............................ 42
Arm parallel conflux check valve, disassembly and assembly ................. 43
Main control valve adjustor, adjusting ....................................................... 43
Logic valve, description ............................................................................ 44
In neutral and boom lowering ................................................................. 44
Boom raising ........................................................................................... 45
Logic valve, disassembly and assembly ................................................... 45
Load check valve, disassembly and assembly ......................................... 47
Straight travel changeover valve, disassembly and assembly ................. 47
Foot relief valve (flow sensing valve), description .................................... 48
Foot relief valve (flow sensing valve), disassembly .................................. 49
Center bypass valve, disassembly and assembly .................................... 50
Load check valve – single, disassembly and assembly ............................ 51
Control valve, replacing ............................................................................ 51

4
 HYDRAULIC SYSTEM;
DIGGING/ HANDLING/
GRADING EQUIPM.; MISC.
EQUIP.

91 WORKING HYDRAULICS;
SERVO HYDRAULICS

912 Working hydraulics

9121 Directional valve; control valve

Hydraulic circuits, ports
Table. Port connection, component
Port Port
name Description name Description
PL Pump P1 port br3 Right travel servo hydraulic port (forward)
PR Pump P2 port ar3 Right travel servo hydraulic port (reverse)
PR1 Pressure source of option port a Arm conflux signal port
BR1 Boom raise port (large chamber) b Boom raise conflux signal port
AR2 Bucket curl port (cylinder extend) - large al3 Arm in servo hydraulic port (cylinder extend)
chamber
BR2 Bucket dump port (cylinder retract) - small bl3 Arm out servo hydraulic port (cylinder retract)
chamber
BL4 Left travel port (forward) R Main return port
AL4 Left travel port (reverse) Rs1 Swing motor boost port
BR3 Right travel port (forward) Pa Arm regeneration valve port
AR3 Right travel port (reverse) Py Pressure boost servo hydraulic port (main)
AL3 Arm in port (cylinder extend) - large Px1 Travel pressure switch port
chamber
BL3 Arm out port (cylinder retract) - small Px2 Attachment pressure switch port
chamber
AL1 Swing port (left) Po Arm conflux port
BL1 Swing port (right) dr1 Drain port
AL2 Option port dr2 Drain port
BL2 Option port dr3 Drain port
al1 Swing servo hydraulic port (left) dr4 Drain port
bl1 Swing servo hydraulic port (right) dr5 Drain port
al2 Option (X1) shuttle block port Y Quickfit valve
bl2 Option (X1) shuttle block port Fr Negative pump control signal port
ar1 Boom lower servo hydraulic port Fl Negative pump control signal port

5
Port Port
name Description name Description
br1 Boom raise servo hydraulic port Ps Arm semi-parallel valve signal port
ar2 Bucket curl servo hydraulic port Pb Boom raise conflux signal port
br2 Bucket dump servo hydraulic port 3Pi Boom lower holding valve servo hydraulic port
4Pi Arm holding valve release signal port Pg1 -
bl4 Left travel servo hydraulic port (forward) Pg2 Boom holding valve primary pressure source
al4 Left travel servo hydraulic port (reverse)

Main control valve, description

This valve block consists of a 4-spool block and a 3-spool block
connected by screws, main spool, main relief valve, port relief
valves, boom & arm holding valve, boom & arm regenerating
valve, arm parallel valve, boom priority logic valve, foot relief
valve, straight travel valve, center bypass valve, and various
check valves such as arm parallel conflux check, back pressure
check, load check etc.

6
 PF1/4
PF1/4 Ps
Pb
dr5 Pa

Bl1
2 2 PF1/4
8 PF1/4
PF1/4
PF1/4
Br1
Pg2
5 Bl2 dr4 3
Br2 A View B
Bl3 B
Pa
Br3 7
PF1/4
Bl4
3Pi
PF1/4

R BR1 PR

M12x1.75
3
2
AR1

7
dr3 1 BR2 AR2
PF1/4
C
BR3 AR3
PF1/4 Py
Y Rs M10x1.5
3 PF1/4
al1

ar1 PF1/4 PF1/4 6

PF1/4 4 Fr a
al2

ar2
D
PF3/8 PF1/4
Pi
al3 View A
1
6 ar3
Px al4

PF1/4
M12x1.75 8
Px1
dr1

PF1/4 5
View C

View E
E
5
1
PL
4 8 M10x1.5
8
AL1 BL1

M12x1.75
AL2 BL2 5
Pa dr2
Pi 4Pi BL3
AL3
PF1/4
Px2 M10x1.5
AL4 BL4
7 4
PF1/4 g1 b F1

PF1/4 PF1/4
6
F
View F View D V1162579

Fig.1 Main control valve, external view 1

1 Main relief valve
2 Boom raise port relief valve
3 Boom lower port relief valve
4 Arm in port relief valve
5 Arm out port relief valve

7
 6 Bucket curl port relief valve
7 Bucket dump port relief valve
8 Option port relief valve

Table. Port connection

Port size Tightening torque Port name
kgf·m (lbf·ft)
ø26 5 ± 0.5 PR, PL, BL3
(M10 x 1.5) (36 ± 4)
ø23 AL1, BL1, AL2, BL2, AL3, AR1, BR1, AR2, BR2, AR3, BR3, AL4, BL4
(M10 x 1.5)
ø38 10 ± 1 R
(M12 x 1.75) (72 ± 7)
PF1 21 ± 2 Rs1
(152 ± 14)
PF3/8 4 ± 0.4 Pi, Po
(29 ± 3)
PF 1/4 3 ± 0.3 al1, al2, al3, al4, ar1, ar2, ar3, bl1, bl2, bl3, bl4, br1, br2, br3, a, b, Fr,
(22 ± 2) Fl, Dd, Ps, Pg2, dr1, dr2, dr3, dr4, dr5, Pa, Pb, Px1, Px2

8
 Main control valve, sectional view
A B
56
C 50

G 43
D D G 39
19
41,44 41,44
E E
63 48
36
62
43
H H

F
36
26
3
L
K K

49 51 49

Section B-B
A C
B
37,38 1 36 32
2 47 33
14
41,44
A

60

12 13
View X
64
Section D-D
42,45 54,57

View Y

X Y
17 46 18
43
36
49
16
15
52
6
BM

BKT
8
5 TR
51
39

Section A-A View A V1162606

Fig.2 Main control valve (sectional view 1) 9

 20-1 20 19

20-2

61

21 36 40 35,53
Section E-E
View W

22

52
39
SW
9

11

OPT 34,34
58 23
Section F-F
10
AM
8

5
TL
14 51
36
24
55

Section C-C

25
31 30
Section G-G 59,64
Dr2 4pi

29 63
31
Section L- L

28

Section K-K 27
Section H-H V1162607

Fig.3 Main control valve (sectional view 2)

10
 Tightening torque: N m Tightening torque: N m
Item Item
(kgf m) (lbf ft) (kgf m) (lbf ft)
29.4 ±2.9 (3 ±0.3) (21.6
1 Valve block (right) - 34 Spool stopper
±2.1)
2 Valve block (left) - 35 Flange -
3 Spool cap - 36 Plug -
147 ±14.7 (15 ±1.5) (108
4 Arm holding valve - 37 Screw
±10.8)
5 Spool plate - 38 Washer
6 Boom spool - 39 Screw 49 ±4.9 (5 ±0.5) (36 ±3.6)
7 Bucket spool - 40 Screw 49 ±4.9 (5 ±0.5) (36 ±3.6)
29.4 ±2.9 (3 ±0.3) (21.6
8 Travel spool - 41 Plug
±2.1)
39.2 3.9 (4 ±0.4) (28.9
9 Slew spool - 42 Plug
±2.9)
10 Arm spool - 43 O-ring -
11 Option spool - 44 O-ring -
12 Parallel check valve - 45 O-ring -
13 Parallel check valve spring - 46 O-ring -
196 ±19.6 (20 ±2) (144.4
14 Orifice assembly 47 O-ring -
±14.4)
15 Check valve - 48 O-ring -
16 Spring - 49 O-ring -
17 Boom holding valve - 50 O-ring -
18 Arm parallel changeover valve - 51 O-ring -
196 ±19.6 (20 ±2) (144.4
19 Check valve (boom, slew) 52 O-ring -
±14.4)
58.8 ±5.9 (6 ±0.6) (43.3
20 Port relief valve 53 O-ring -
±4.3)
19.6 ±2 (2 ±0.2) (14.4
201 Lock nut 54 Name plate -
±1.4)
Boom back pressure check 58.8 ±5.9 (6 ±0.6) (43.3
21 55 Main relief valve 98 ±9.8 (10 ±1) (72 ±7.2)
valve ±4.3)
196 ±19.6 (20 ±2) (144.4 58.8 ±5.9 (6 ±0.6) (43.3
22 Load check valve (travel) 551 Lock nut
±14.4) ±4.3)
Straight travel changeover 58.8 ±5.9 (6 ±0.6) (43.3 58.8 ±5.9 (6 ±0.6) (43.3
23 552 Lock nut
valve ±4.3) ±4.3)
24 Logic valve 98 ±9.8 (10 ±1) (72 ±7.2) 56 Eye bolt -
25 Main parallel check valve 98 ±9.8 (10 ±1) (72 ±7.2) 57 Rivet -
196 ±19.6 (20 ±2) (144.4 14.7 ±2 (1.5 ±0.2) (10.8
26 Load check valve 58 Orifice screw
±14.4) ±1.4)
58.8 ±5.9 (6 ±0.6) (43.3
27 Bucket conflux valve 59 Screw 49 ±4.9 (5 ±0.5) (36 ±3.6)
±4.3)
28 Arm regenerating valve 98 ±9.8 (10 ±1) (72 ±7.2) 60 Screw 98 ±9.8 (10 ±1) (72 ±7.2)
58.8 ±5.9 (6 ±0.6) (43.3
29 Center bypass valve (boom) 98 ±9.8 (10 ±1) (72 ±7.2) 61 Port relief valve
±4.3)
196 ±19.6 (20 ±2) (144.4
30 Center bypass valve (Arm) 98 ±9.8 (10 ±1) (72 ±7.2) 62 Load check valve (bucket)
±14.4)
58.8 ±5.9 (6 ±0.6) (43.3 Load check valve (option, 196 ±19.6 (20 ±2) (144.4
31 Foot relief valve 63
±4.3) arm) ±14.4)
29.4 ±2.9 (3 ±0.3) (21.6
32 Signal orifice - 64 Screw
±2.1)
33 Plug 98 ±9.8 (10 ±1) (72 ±7.2)

11
 Pressure relief valve, troubleshooting
• If an abnormal condition is detected, determine if the
malfunction is in the control valve, main pump, servo hydraulic
pump or the circuit components such as: remote control valve,
motor, or the center passage.
• Check the main relief, port relief, and servo hydraulic relief
pressure.
• Check the P1/P2 pump flow rate.
• Check the hoses and piping for damage.
• Check the filters and hydraulic oil for contamination.

Table. Troubleshooting
Phenomenon Cause Remark
Pressure does not • Main poppet of relief valve is sticking and • Check for contamination on the poppet.
rise. valve is open. • Confirm that each component slides smoothly.
• There is contamination on the poppet or • Clean all the components thoroughly.
seat.
Unstable relief • Damaged main poppet seat or servo • Replace damaged component.
pressure. hydraulic poppet seat of relief valve. • Clean all the components thoroughly.
• Main poppet is sticking.
Relief pressure is • Wear due to foreign matter. • Disassemble and clean the valve.
incorrect. • Damaged pilot seat due to foreign matter. • Adjust the relief pressure.
• Loosened lock nut or adjusting screw.
Oil leak • Damaged main poppet seat or pilot poppet • Replace damaged or worn component. Confirm
seat due to foreign matter. that each component operates smoothly before
• Worn O-ring. reassembling.
• Sticking component due to foreign matter. • Confirm that there are no scratches, nicks, or
contamination present before reassembling.

Main control valve troubleshooting

• If an abnormal condition is detected, determine if the
malfunction is in the control valve, main pump, servo hydraulic
pump or the circuit components such as: remote control valve,
motor, or the center passage.
• Check the main relief, port relief, and servo hydraulic relief
pressure.
• Check the P1/P2 pump flow rate.
• Check the hoses and piping for damage.
• Check the filters and hydraulic oil for contamination.

Table. Troubleshooting
Phenomenon Cause Remark
Travel does not Malfunctioning travel crossover relief valve. Measure travel relief valve pressure.
occur. • Contamination between main poppet and • Disassemble and clean the valve. If damaged,
Slow to start up seat. replace the assembly as a unit.
(sluggish). • Contamination between servo hydraulic • Same as above.
poppet and seat. • Smooth sticking poppet with crocus cloth.
Slow response.
• Sticking main poppet. • Replace spring.
• Broken or fatigued spring. • Remove contamination.
• Clogged main poppet orifice.
Clogged orifice in servo hydraulic circuit. Remove contamination.

12
Phenomenon Cause Remark
Machine does not Malfunctioning straight travel valve. Measure servo hydraulic pressure.
travel straight • Sticking spool. • Smooth sticking spool with crocus cloth.
during • Broken or fatigued spring. • Replace spring.
simultaneous • Excessive clearance between casing block • Replace spool.
travel and digging and spool. • Remove contamination.
unit operation. • Clogged orifice in spool.
Malfunctioning 3 spool or 4 spool side Measure servo hydraulic pressure.
center bypass valve.
• Sticking spool. • Smooth sticking spool with crocus cloth.
• Broken or fatigued spring. • Replace spring.
• Excessive clearance between right or left • Replace spool, right or left casing.
casing and spool. • Remove contamination.
• Clogged oil passage in spool.
Malfunctioning logic valve.
• Contamination between poppet and seat. • Disassemble and clean valve.
• Damaged poppet or seat face. • If damaged, replace poppet or seat.
• Broken or fatigued spring. • Replace spring.
Malfunctioning track motor relief valve. See 4411, Track motor, troubleshooting.
Excessive drift of Excessive clearance between casing and Replace control valve section.
cylinder in neutral spool.
position. Spool is not completely in neutral position. Measure primary, secondary servo hydraulic
• Contamination between casing and spool, or pressure.
sticking spool. • Disassemble, clean and smooth sticking part with
• Broken or fatigued spring. crocus cloth.
• Clogged servo hydraulic circuit. • Replace the spring.
• Remove the contamination.
Malfunctioning port relief valve. Measure port relief valve pressure.
Malfunctioning anti-cavitation check valve. • Disassemble and clean.
• Contamination between poppet and casing. • Replace spring.
• Broken or fatigued spring.
When extending Malfunctioning load check valve. • Disassemble and clean. If damaged, replace it.
cylinder, at first it • Contamination between poppet and casing. • Smooth sticking poppet with crocus cloth.
retracts. • Sticking poppet. • Replace spring.
• Broken or fatigued spring.
Bucket, boom or Malfunctioning main spool. Measure primary, secondary servo hydraulic
arm alone does • Excessive clearance between casing and pressure.
not operate. spool. • Replace control valve section.
Slow to start up • Contamination between casing and spool. • Disassemble and clean.
• Sticking spool. • Smooth sticking spool with crocus cloth.
(sluggish).
• Broken or fatigued return spring. • Replace spring.
Slow response.
• Clogged servo hydraulic circuit. • Remove contamination.
Malfunctioning main relief valve. Measure main relief valve pressure.
Malfunctioning port relief valve. Measure port relief valve pressure.
Malfunctioning servo hydraulic relief valve. Measure servo hydraulic pressure.
Clogged screen filter of joystick. Clean filter screen.
Slew priority Malfunctioning logic valve. • Smooth sticking spool with crocus cloth.
function does not • Replace spring.
occur. • Replace spool, right or left casing.
• Remove contamination.
Clogged orifice in servo hydraulic circuit. Remove contamination.

13
Phenomenon Cause Remark
Slew does not Malfunctioning center bypass valve. • Disassemble and clean.
occur. • If damaged, replace poppet or seat.
• Replace spring.
Despite lever Malfunctioning foot relief valve. Measure foot relief valve pressure.
being in neutral, • Contamination between poppet and seat. • Disassemble and clean. If damaged, replace the
negative control • Broken or fatigued spring. assembly as a unit.
does not occur, • Clogged poppet orifice. • Replace spring.
• Clogged filter. • Remove contamination.
and fails to
• Replace filter screen.
minimize flow.

14
 General, precautions

Removal, precautions
• Thoroughly clean the control valve prior to removal from the
machine.
• Tag all hoses prior to disconnecting from the control valve.
• Cap all hoses and plug all ports to prevent contamination from
entering.
• Use eye bolts to lift the control valve. Do not sling on the relief
valves or spool caps.

WARNING
The control valve is heavy. Take appropriate safety precautions
when handling.

Disassembly, precautions
• Do not use excessive force, sharp or high hardness tools to
disassemble the control valve.
• Handle the components carefully, protect the highly polished
precision finish. If the surface is damaged it will cause internal
oil leakage and malfunction.
• Match mark the parts to indicate original location and position
during reassembly.
• Take care not to mix the parts of the various check valves and
flow valves.
• Inspect and analyze all failures. – Determine the root cause!

Assembly, precautions
• Clean all parts with cleaning solvent and dry with compressed
air.
• Rework damaged parts, polish minor burrs, nicks, score marks
or sharp edges with fine emery and crocus cloth. Prepare all
replacement parts.
• Coat the sliding parts with clean hydraulic oil.
• Replace the seals, O-rings and back-up rings.
• Use a torque wrench to tighten the screws and plugs to the
specified torque.
• Take care not to interchange the spools.

General, inspection

Table. Inspection methods

Part Remark
1 Housing
• Check for flaws, cracks and corrosion, and • If there are score marks, rust and corrosion, correct with #2000
check for hidden cracks by use of various sand paper and crocus cloth.
detection methods. i.e. magnetic flux or dyes. • If there is damage that cannot be repaired, replace with a new
component.
• Valve housing is a non-serviceable part. If there • Housing bore: spool and sliding parts.
is damage, replace the control valve assembly. Especially around the pressure holding areas as applied to:
Seat: Seat of check valve.
Port seal: O-ring contact surface.
Seal: Main relief, port relief bore contact surface.

15
 Part Remark
2 Spool
• Check for nicks, scratches, rust and corrosion • If there are nicks, scratches, rust and corrosion, correct with
on the outer diameter. #2000 sand paper and crocus cloth.
• If a flaw is found on the outer diameter, check • The spool is a non-serviceable part. If damaged replace the
the relevant housing bore. control valve assembly.
• Insert the spool into its bore and operate • If it binds slightly try polishing the spool with crocus cloth.
forward/reverse while rotating.
• Check if there is a flaw on the check valve seat • If there is a flaw or a partial contact trace on the seal face seat,
and the check valve, inside the spool. replace the valve.
• Insert the check valve into the spool, and • If it sticks, replace it.
operate it forward/reverse.
• Check the spring. • If there is damage or heat discoloration replace it.
3 Return spring, rear side.
• Check the spring, spring guide, spool cap and • If there is wear or damage, replace the part.
cover for rust, corrosion, wear, and damage.
4 Load check valve.
• Check the seat of check valve. • If there is a flaw or partial contact trace on the seat, replace the
part.
• Check the spring. • If there is damage replace it.
5 Orifice
• Check if the foot relief valve orifice is clogged. • If clogged, bore with wire.

NOTE!
Do not distort or change the orifice size.
6 Boom holding valve, servo hydraulic logic
valve
• Check the poppet seat for flaws. • If there is a flaw or partial contact trace on the seat, replace the
part.
• Insert the poppet, and operate it forward/ • If it sticks, replace it.
reverse.
7 Main relief, port relief valve.
• Check the seat for flaws. • If there is a flaw or partial contact trace on the seat, replace it.
• Check if the orifice is clogged. • If clogged, bore with wire.
• Insert the poppet, and move it forward/reverse. • If it sticks replace it.
• Check the spring. • If there is damage or heat discoloration, replace it.
• It is difficult to judge the relief valve for damage
by eye, therefore check the operating condition
carefully.

General, tools
Before disassembling or assembling the valves, prepare the
following tools:

Table. Tools
No. Tool Size Quantity
1 Vise 1
2 Socket 27 mm 1
3 32 mm 1
4 41 mm 1
5 46 mm 1

16
 No. Tool Size Quantity
6 Allen wrench 4 mm 1
7 5 mm 1
8 6 mm 1
9 8 mm 1
10 10 mm 1
11 12 mm 1
12 14 mm 1
13 17 mm 1
14 19 mm 1
15 Torque wrench 75 ~ 4000 kgf·cm Various
(5 ~ 300 ft·lbs)
16 Loctite # 262 1

Prepare the following tools, also:

• M6 screw (to remove cut-off valve, conflux flow valve, travel
priority valve)
• Magnet bar (to remove shuttle valve ball, negative control relief
valve)
• Holder for main spool (to protect the spool when clamped in
the vise)

Holder (Material: Brass)

A. Tool no : 8932-00030 B. Tool no : 8932-00610

90 "A" PF 1
4
"B"

22 9.2
11
10
30

R1
10
28
50

34.5
R1 M10 x 30

2 25 5.3 M10 V1089494

Fig.4 Holder
A Hexagon holder (2 pieces)
B Screw (M5 × 60)

Table. Holder usage

φD Holder Application
28.2 41 Main spool
15.9 32 Straight travel changeover spool

Main spool, disassembly and assembly

(For assembly, reverse disassembly procedures)

Op. no. 00000

Tools:
When disassembling, mark each part to indicate original location
and position during assembly.

17
 3 2 1

V1004716

Fig.5 Main spools

1 Remove screw (1), and remove cover (2).

- Tools: Allen wrench 12 mm
- Tightening torque: 15 kgf·m (108 lbf·ft)
NOTE!
When assembling, make sure that the O-ring is installed
before assembling the cover.
2 Pull out the spool subassembly.
NOTE!
Pull out the spool slowly confirming the housing condition.
V1004717

Fig.6 Removal, spools

3 Hold spool with holder and vise, and loosen spool cap (3).
- Tools: Allen wrench 12 mm
3 - Tightening torque: 15 kgf·m (108 lbf·ft)
NOTE!
Remove oil from the spools and holder.
V1004718
NOTE!
Fig.7 Disassembly, spools
When assembling, note spring guide direction.
4 Remove spools cap (3) and remove spring guides (4 & 7),
spring (5) and spacer (6).

3 7
6

4 V1004719

Fig.8 Removal, spring etc.

18
 5 Only for the arm and the boom spools, remove cap (8), and
pull out spring (9) and check valve (10).
- Tools: Allen wrench 8 mm
- Tightening torque: 6 kgf·m (43 lbf·ft)

10 V1004720

Fig.9 Removal, check valve etc.

Main relief valve, description

Py servo hydraulic signal: OFF
Hydraulic oil supplied from the pump flows to chamber (3) through
orifice (2) of main poppet A.
As section area d1 > d2, main poppet A will not move.
B
C A
D d1
d2

P
(Py)

1
E
4 3 2 T V1004721

Fig.10 Main relief valve

A Main poppet E Servo hydraulic signal: OFF

B Servo hydraulic poppet P From pump port
C Spring T Tank passage
D Piston

If the pressure exceeds set value of spring C, servo hydraulic

poppet B will open so that the oil flows to tank passage through
hole (4). The pressure in chamber (3) will be lowered.

V1004722

Fig.11 When the pressure reaches set value

A The oil supplied when servo hydraulic poppet B is opened (the

pressure of chamber (3) is low) creates a pressure differential
d1
d2 between front and rear of orifice (2), so the “pressure of chamber
(1) × d2” becomes larger than “pressure of chamber (3) × d1”. The
P circuit pressure is controlled to constant level as main poppet A
opens to allow hydraulic oil flow to tank passage.
1

4 3 2 T V1004723

Fig.12 Hydraulic oil flow to tank passage

19
 Pressurized (350 kgf/cm2)
Py servo hydraulic signal: ON
C Servo hydraulic pressure moves piston D and the set pressure of
D spring C is increased, so pressure setting is raised.

(Py)

E V1004724

Fig.13 Pressure setting is raised

E: Servo hydraulic signal ON

Main relief valve, adjustment

Adjustment of the limiting pressure

Measuring condition
- Place the machine in the service position B. See091, Service
positions
- Hydraulic oil temperature : 50 ±5°C (122 ±41°F)
- Working mode: “P” mode ( North America : H mode )
- Measuring location : P2 gauge ports at hydraulic main pump
- At full stroke end of bucket in/out (at 1 pump flow condition)
NOTE!
Adjustment temperature should be kept within 50 ±5°C (122
±41°F), as unnecessary relief (valve loading) causes rapid
temperature rise.

WARNING
Hot hydraulic oil and hydraulic oil under pressure may result in
severe personal injuries

WARNING
Leaking high-pressure hydraulic hoses may cause severe
injuries. Fine jets have high penetrating capacity on bare skin.

Measurement
• Connect oil pressure gauge (600 kgf/cm2, 8530 psi) to the
quick coupler.
• Start the engine, set to “ P ” mode, and measure the main
pressure with the engine at high idle.
• Operate the bucket cylinder to the end of its stroke to check the
low/high relief pressures.
• Operate the switch on the upper part of operating lever (right)
to measure the boost pressure.

Hydraulic pressure
See 9121, Main control valve, specifications

20
 a4 Pi2

Dr 2

a1 a2 View A
A 2
4 V1013968

Fig.14 Pressure measuring port of hydraulic pump

1 Quick coupler 2 Hose (pressure gauge) 3 Pressure gauge 4 Cap

1 2 3 4 5 6 7 8

NOTICE
If the relief valve pressure setting is wrong, hydraulic devices may
be damaged, and the result could be dangerous. Make absolutely
sure that the pressure setting is not higher than specified.

YZ

3
Y Z

V1013893

Fig.15 Main relief valve

1 Screw (low 6 Cartridge

pressure)
2 Lock nut 7 Regulating spring
3 Screw (high 8 Servo hydraulic
pressure) poppet
4 Lock nut Y Piston surface
5 Piston Z Screw (high
pressure) surface

High pressure adjustment (Boost pressure)

1 Remove the servo hydraulic hose connected to the relief
valve, and plug the hose end.
2 Loosen lock nut (2), and turn adjusting screw (1) clockwise
until fully seated(Y and Z).
3 Loosen lock nut (4), and turn adjusting screw (3) as follows To
increase pressure, turn clockwise.

21
 To decrease pressure, turn counterclockwise.
NOTE!
1/4 rotation will change it by about 46 kgf/cm2 (652psi.)
4 Hold adjusting screw (3) securely and tighten lock nut (4).
NOTE!
Tightening torque : 6 kgf·m (43.3 lbf·ft)
5 Readjust the low pressure setting to specifications.
6 Reconfirm the high/low pressure settings.

Low pressure Adjustment (Standard pressure)

1 Remove the servo hydraulic hose connected to the relief
valve, and plug the hose end.
2 Loosen lock nut (2), and turn adjusting screw (1) as follows
To increase pressure, turn clockwise.
To decrease pressure, turn counterclockwise.
3 Hold adjusting screw (1) securely and tighten lock nut (2).
NOTE!
Lock nut (2) tightening torque : 6kgf·m (43.3 lbf·ft)
4 Reinstall the relief valve servo hydraulic hose.

NOTICE
Reconfirm the low pressure setting, then check the high pressure
setting using the power boost function. Do not try to adjust the
high pressure setting without proper gauges.

Main relief valve, disassembly and assembly

(For assembly, reverse disassembly procedures)

Op. no. 00000

Tools:
1 2 3 4 1 Hold adjusting screw (1) and loosen lock nut (2).

5 V1004725

Fig.16 Main relief valve

2 Hold cap (4) and loosen lock nut (3).

3 Remove cap (4) and remove the cartridge.
4 Remove sleeve (6) and pull out piston (7), spring (8) and
orifice (9).
NOTE!
Do not remove servo hydraulic seat, because it is press
fitted.
6 5 Loosen each screw and nut.
7
8
9 V1004726

Fig.17 Removal, piston etc.

22
 Table. Dimensions
Item Dimension
1 Adjusting screw 22 mm
2 Lock nut 30 mm
3 Lock nut 30 mm
4 Cap 30 mm
5 Sleeve 27 mm

Main pressure relief valve, replacing

Op. no. 912-067

WARNING
Risk of crushing injury.
The hydraulic system could respond slowly at low temperatures
and could cause unexpected machine movements.
Operate carefully until the hydraulic system has reached
operating temperature.

WARNING
Hot hydraulic oil and hydraulic oil under pressure may result in
severe personal injuries

WARNING
Lower the digging units to the ground and stop the engine (start
switch ON position). Operate the control levers several times to
release the remaining pressure in the hydraulic piping.
1 Place the machine in the service position B. See 091,
Service positions.
2 Remove screws and main control valve compartment cover.

V1161661
1 2
Fig.18 Cover, removal
1 Screws
2 Cover

23
 3 Remove hose and main relief valve.
4 Install a main relief valve.
NOTE!
Tightening torque : 147.1 ±14.7 N m (108.3 ±10.8 lbf ft)
5 Adjust the main pressure and test the machine. See : Main
relief valve, adjustment page 20
6 Install main control valve cover.

V1161706
1 2
Fig.19 Main relief valve, replacing
1 Hose
2 Main relief valve

Port relief valve, description

Overload operation
D d1 2 B d2 1 Hydraulic oil from the cylinder port (P), flows through the orifice
of piston A to chamber (2). Since section area d1 > d2, main
poppet B can not move.

C 4 5 6 T A
V1004727

Fig.20 Normal condition

If the pressure reaches set value of spring C, servo hydraulic

poppet D will open and the oil flows to tank through the lateral
hole and circular passage, then the pressure in chamber (2) will
be lowered.
The oil supplied when servo hydraulic poppet D is opened (the
V1004728 pressure of chamber (2) is low) creates a pressure differential
Fig.21 Pressure reaches set value between front and rear of the orifice in piston A (chamber (1) and
(2)), so piston A moves to the left and stops at the end of servo
hydraulic poppet D.
D d1 2 B d2 1 The oil in chamber (1) flows to tank passage through the orifice
of piston A, through the lateral hole and circular passage.

4 5 6 T A V1004729

Fig.22 Oil creates pressure differential

As the pressure is lowered front and rear of the orifice in servo

hydraulic poppet D, “pressure of chamber (1) × d2” will be higher
than “pressure of chamber (2) × d1”. Therefore, poppet B opens
and hydraulic oil from the cylinder port flows directly to tank
passage.

V1004730

Fig.23 Oil flows to tank passage

24
 Anti–cavitation operation
d2 B Section area of poppet B is larger than d1, and since pressure in
d1
the cylinder port is usually higher than pressure in the tank port,
the valve is closed. However if the pressure in the cylinder port
decreases lower than the tank port (near to negative pressure),
P poppet B is opened by tank pressure by as much as the area
difference of d1 and d2. Then the tank passage return oil will flow
to the cylinder port to prevent cavitation.
NOTE!
T V1004731 See 9121, 2 stage port relief valve, description
Fig.24 Preventing the cavitation

25
 Port relief valve pressure, measuring and
adjusting

Measuring condition
- Place the machine in the service position B. See091, Service
positions
- Hydraulic oil temperature : 50 ±5°C (122 ±41°F)
- Working mode: “P” mode ( North America : H mode )
- Adjusting the pump displacement
- Main relief valve pressure : 44.1 MPa (450 kgf/cm2) (6400 psi)
(441.3 bar)
NOTE!
Adjustment temperature should be kept within 50 ±5°C (122
±41°F), as unnecessary relief (valve loading) causes rapid
temperature rise.

WARNING
Hot hydraulic oil and hydraulic oil under pressure may result in
severe personal injuries

WARNING
Leaking high-pressure hydraulic hoses may cause severe
injuries. Fine jets have high penetrating capacity on bare skin.

Measurement
• Connect oil pressure gauge (600 kgf/cm2, 8530 psi) to the P1/
P2 gauge ports.
• Start the engine, set to “P” mode, and measure the main
pressure with the engine at high idle.
• Condition of digging unit to be measured.
- For the working equipment, set each cylinder to the end of
its stroke.
- For slewing, put the bucket against an immovable object or
put it in a trench.
- For travel, fit a pin between the sprocket and frame to lock
the sprocket against the frame.
- Operate the switch on the upper part of operating lever
(right) to measure the boost pressure.

Hydraulic pressure
See 9121, Main control valve, specifications.

Primary pump supply to each actuator and test port

location.

Table. Port connection

Plug Pump Actuator (test port)
(1) P2 (PR) pump • Boom cylinder • Bucket cylinder • Right travel motor (on the motor head)
(2) P1 (PL) pump • Slew motor (on the motor head)• Option digging unit• Arm cylinder• Left travel motor
(on the motor head)

26
 a4 Pi2

Dr

a1 a2

1 2
V1013903

Fig.25 Pressure measuring port of hydraulic pump

1 Quick coupler for P1 (Gauge port) PF 1/4 × 15
2 Quick coupler for P2 (Gauge port) PF 1/4 × 15

Pressure measuring port of track motor

See 4411, Track motor, description

Pressure measuring port of slew motor

See 4412, Swing motor, description

Adjustment of the pump displacement

(When measurement Port relief valve (boom, arm, bucket,
option)
NOTE!
For the correct setting of the limiting pressure of the port relief
valve, connect the hoses and follow the procedures for adjusting
the pump displacement.
NOTE!
Do not adjust the main relief pressure and pump displacement
when adjusting the slewing relief pressure only.
1 Removal a hose (11) and a fitting (4) from servo hydraulic
pump a3 port.
2 Mount a tee (12) and hoses (11, 13, 14) to servo hydraulic
pump a3 port.
3 Disconnect a hose (5) from fitting (6) and plug it
4 Install a jumper hose (14) to a fitting (6).
5 Disconnect hoses (7, 10) from tee (8) and plug it.
6 Removal a tee (8) from negative port (Pi1).
7 Install a fitting (9) and a jumper hose (13) to negative port (Pi1).
8 Checking and adjustment the port relief pressure of each port
relief valve.
9 Reconnect the servo hydraulic hoses to their original position
upon completion of checking and adjusting pressures.

27
 5 15 6 15 7
(2-Fr) (2-Fl)

5 6 7 8 10 9 10
(2-Fr) (2-Fl) 45-A
45-A 14

1 1
Psv 13 Psv Pi1
2 Pi2 Pi1 Pi2
2
3 3

4 12
a3
a3

11 11

View A View B
V1013986

Fig.26 Connect the pump to the control valve

View A Original servo hydraulic line View B Connected servo hydraulic line for adjusting the pump
displacement
1 Main pump 9 Fitting (PF1/4)
2 Servo hydraulic pump 10 Hose (flow control solenoid valve(45-A)
3 Servo hydraulic pump inlet port 11 Hose
4 Fitting (outlet port) 12 Tee - 3 port (PF1/4)
5 Hose (from main control valve (2-Fr)) 13 Jump hose (P1)
6 Tee (PF1/4) 14 Jump hose (P2)
7 Hose (from main control valve (2-Fl) port) 15 Plug
8 Tee (PF1/4)

Port relief valve pressure, adjustment

(For boom, arm, bucket)

28
 1 NOTE!
For the correct setting of the pressure of the relief valve, connect
hoses and follow the procedures for adjusting the pump
displacement.
NOTE!
2 Do not adjust the port relief valve unnecessarily.

3 Symptoms of faulty port relief valve :

• Main relief valve high/low pressures can not be adjusted.
• Attachment hoses rupture repeatedly.
NOTE!
Adjustment temperature should be kept within 50 ±5 °C (122 ±41
°F), unnecessary relief valve loading causes rapid temperature
rise. If pump displacement is not decreased, the port relief valve
will open at lower than specified pressure.
* Operate the hydraulic cylinder of the circuit to be measured to
the end of its stroke.
1 Decrease the displacement of the pump.
2 Increase the main relief valve pressure to exceed 450
kgf/cm2 (6525 psi), approximately 1/2 turn.
3 Loosen lock nut (2), and turn adjusting screw (1) as follows :
V1013895 To increase pressure, turn clockwise. To decrease pressure,
Fig.27 Port relief valve, adjustment turn counterclockwise.
4 Hold adjusting screw (1) securely and tighten lock nut (2).
5 After completion of adjustment, reset the main relief valve
1 Adjusting screw 2 Lock nut 3 Cartridge
high/low pressures to specifications.

Slew motor port relief valve pressure, adjustment

See 4412, Slew motor, adjustment

Port relief valve pressure, adjustment (When installing or

dismantling the line rupture valve
See 9123, Port relief valve pressure, adjustment (when installing
or dismantling the line rupture valve)

Port relief valve, disassembly

(For assembly, reverse disassembly procedure)

Op. no. 00000

Tools:
When disassembling, mark each part to make assembling easier.
NOTE!
Do not disassemble pressure adjusting part.

1 1 Remove sleeve (1) and cartridge form the main control

valve.
- Tools: Spanner 32 mm
- Tightening torque: 6 kgf·m (43 lbf·ft)
NOTE!
Set pressure is different according to position. Be sure to
assemble it to its original position.
2 V1004735

Fig.28 Removal, sleeve

29
 2 Remove cap (2) and pull out spring (3) and servo hydraulic
poppet (4).
- Tools: Socket, spanner 27 mm
- Tightening torque: 6 kgf·m (43 lbf·ft)

3
4 V1004736

Fig.29 Removal, spring and servo hydraulic poppet

9 8 6,7 5 3 Remove servo hydraulic seat (5) and pull out springs (6, 7),
piston (8) and main poppet (9).

5
6
7
8

9 V1004737

Fig.30 Removal, servo hydraulic seat, spring and

main poppet

30
 Boom holding valve, description

Spool in neutral
3Pi servo hydraulic signal : OFF
The position of piston A is as illustrated and servo hydraulic
pressure (Pg2) is isolated from chamber Y. Therefore, the
positions of piston B and poppet C become as shown, and
passage (5) and (6) will be isolated from poppet C. As chamber
(1) is connected to chamber (2) through orifice (4), pressure Pc
is obtained. As poppet E is closed because section area d1 > d2,
chamber (2) and (3) are completely isolated.
Z
5
D 6
C
B E
1 d1
Y (Pc) 2 4

(Pv) 3 d2
P
Pg2
7
F
dr4

H
View Z A
3Pi T V1004738

Fig.31 Boom holding valve

A Piston F Boom spool

B Piston P Boom cylinder head side
C Poppet H High pressure supply passage
D Check valve T Tank passage
E Poppet

Spool operating
Boom raising [Pv > Pc] (3Pi servo hydraulic signal : OFF)
As chamber (1) is connected to chamber (2) through orifice (4),
pressure (Pc) is obtained and poppet E will open. The oil in high
pressure supply passage flows to cylinder, piston side.

31
 Z

1 E

4
(Pc) 2

(Pv) 3 P
Pg2

H
View Z
3Pi T V1004739

Fig.32 Boom raising

P Boom cylinder head side 3Pi Servo hydraulic pressure

H High pressure oil supply passage T Tank passage
E Poppet

Boom lowering [Pc > Pv] (3Pi servo hydraulic signal : ON)
When servo hydraulic pressure (3pi) is applied, piston A moves
up and servo hydraulic pressure (Pg2) flows to chamber Y. Piston
B and poppet C move to the right, so passage (5) and (6) are
connected.
As chamber (3) is connected to the tank passage (by spool
moving to left), the oil in chamber (1) opens check valve D through
passage (5) and (6), and then flows to tank passage through
passage (7). Therefore, pressure Pc is applied to (d1 area – d2
area). Poppet E is opened and the oil returned from the cylinder,
piston side, now flows to tank passage.
Z 6
5
D 6
C
B E
1
d1
Y (Pc) 2

(Pv) 3 d2
P
Pg2
7

dr4

A
3Pi View Z T V1004740

Fig.33 Boom lowering

A Piston P Boom cylinder piston side

B Piston G Drain port
C Poppet 3Pi Servo hydraulic pressure port
D Check valve T Tank passage
E Poppet

32
 Boom holding valve, disassembly
(For assembly, reverse disassembly procedure)

Op. no. 00000

Tools:
When disassembling, mark each part to make assembling easier.
Z 1
2

4
7

View Z 5 V1004741

Fig.34 Boom holding valve

Main body check valve

1 Remove screw (1) and remove cover assembly (2).
NOTE!
When reassembling, make sure that the o-ring is installed
on housing inlet before assembling the cover.
3
2 Pull out spring (3) and poppet (4).
4 V1004742 Tools : Allen wrench 10 mm
Fig.35 Main body check valve Tightening torque : 10 kgf·m (72 lbf·ft)

Selector valve
3 Remove cap (5) and pull out piston (6) and spring (7).
Tools : Allen wrench 6 mm
Tightening torque : 3 kgf·m (22 lbf·ft)
5

6
7 V1004743

Fig.36 Selector valve

Cover assembly
8 4 Remove cap (8) and pull out spring (9) and check poppet
9 (10)
Tools : Allen wrench 8 mm
10 Tightening torque : 5 kgf·m (36 lbf·ft)

11 12 13 14 15 16
V1004744

Fig.37 Cover assembly

33
 8
9
10 V1004745

Fig.38 Spring etc, removal

5 Remove cap (11) and pull out piston (12).

Tools : Allen wrench 10 mm
Tightening torque : 6 kgf·m (43 lbf·ft)

12

11 V1004746

Fig.39 Piston, removal

6 Remove cap (16) and pull out spring (15) and poppet (14).
Tools : Allen wrench 8 mm
Tightening torque : 5 kgf·m (36 lbf·ft)
7 Pull out sleeve (13) by tapping the left side of cover lightly.
16
NOTE!
15 Take care not to damage the surface edge (φ5) of sleeve.

14 V1004747

Fig.40 Poppet, removal

34
 Boom regenerating valve, description

H
BR1 AR1

A
ar1

B C T P V1004758

Fig.41 Boom regenerating valve

A Check valve H Boom holding valve

B Spring P Center bypass passage
C Back pressure check valve T Tank passage

Servo hydraulic pressure (ar1) pushes the boom spool left (boom
lowering) and pressurized oil from the pump opens the load check
valve and flows through the U-shaped path, the circular notch of
the spool, and port AR1 to the cylinder, rod side.
The return oil flows from port BR1, to the circular notch of the
spool, where it passes through the path inside the spool to check
valve A. As the oil pressure rises it overcomes the spring force,
opens the check valve and merges with the flow through port AR1
to the cylinder, rod side.
This process prevents cylinder cavitation during boom lowering.

35
 Boom back pressure check valve, disassembly
and assembly
(For assembly, reverse disassembly procedure)

Op. no. 00000

Tools:
When disassembling, mark each part to make assembling easier.
1 2 3 1 Remove cap (1) and pull out spring (2) and poppet (3).
- Tools: Socket wrench 30 mm
- Tightening torque: 6 kgf·m (43 lbf·ft)

V1004765

Fig.42 Boom back pressure check valve

Arm holding valve, description

Spool in neutral
4Pi servo hydraulic signal : OFF
A
D
Dr2 4Pi

d1

B
d2

2 (Pc)

(Pv) 3
4

H T V1004748

Fig.43 Arm holding valve

A Spool
B Poppet
C Arm spool
D Servo hydraulic signal port
R Arm rod

36
H High pressure oil supply passage
T Tank passage

Spool A is positioned as shown, and chamber (1) and drain (Dr2)

are isolated. As chamber (1) is connected to chamber (2) through
orifice (4), the pressure in chamber (1) will be Pc. Since area d1
> d2, poppet B can not move, and chamber (2) and chamber (3)
are isolated to hold the arm in position.

Spool operating
Arm out [Pv > Pc] (4Pi servo hydraulic signal : OFF)
A
D
Dr2 4Pi

2 (Pc)

(Pv) 3
4

H T V1004749

Fig.44 Arm out

A Spool
B Poppet
D Servo hydraulic signal port
R Arm rod
H High pressure oil supply passage
T Tank passage

As chamber (1) is connected to chamber (2) through orifice (4),

the pressure will be Pc and poppet B will open. Oil (Pv) in the high
pressure supply passage is supplied to the cylinder rod side
through chamber (3).
Arm in [Pc > Pv] (4Pi servo hydraulic signal : ON)

37
 A
D
Dr2 4Pi

d1

B
d2

2 (Pc)

(Pv) 3

T V1004750

Fig.45 Arm in

A Spool
B Poppet
D Servo hydraulic signal port
R Arm rod
T Tank passage

When servo hydraulic pressure (4pi) is applied, spool A moves

left, chamber (1) and drain (Dr2) are connected. The oil in
chamber (1) drains, and the pressure in chamber (2) decreases.
When pressure Pc applied by (area d1 - area d2), poppet B will
open and the oil returned from the cylinder, rod side, flows to tank
passage.

Arm holding valve, disassembly and assembly

(For assembly, reverse disassembly procedure)

Op. no. 00000

Tools:
When disassembling, mark each part to make assembling easier.
1 Screw (1) and remove cover (2).
- Tools: Allen wrench 6 mm
- Tightening torque: 5 kgf·m (36 lbf·ft)
NOTE!
When assembling, make sure that the O-ring is installed on
manifold inlet before assembling.

38
 2

1 A

V1013951

Fig.46 Arm holding valve

A Arm port relief valve

2 Pull out spring seat (3), spring (4) and poppet (5).
5

3
4 V1004752

Fig.47 Removal, spring etc.

6 7 8 9 3 Cover assembly
Remove cap (6) and pull out spring (7), seat (8) and spool
(9).
- Tools: Allen wrench 6 mm
- Tightening torque: 3 kgf·m (22 lbf·ft)

8
7 V1013952

Fig.48 Removal, spool

Arm regenerating valve, description

Servo hydraulic pressure (al3) pushes the arm spool right (arm
in) blocking the center bypass passage, and pressurized oil from
the pump opens the load check valve and flows through the U-
shaped path, the circular notch of the spool, and port AL3 to the
cylinder, piston side.

39
 J

(PB)
BL3
(PA)

AL3

T
F
al3

H P G B 1 2 C D E V1004759

Fig.49 Arm regenerating valve

A Check valve E Check valve P Center bypass passage

B Piston F Arm regenerating valve R Reserve passage
C Spool G Check valve for conflux T Tank passage
D Spring H High pressure supply passage J Arm holding valve

Pressure on rod side is high [PB > PA ]

The return oil flows from port BL3, to the circular notch of the
spool, to restricted passage (1) and (2) where the pressure rises,
moving spool C and opening a narrow path to check valve A.
When the check valve opens the oil flows via the passage in the
spool to merge with the flow through port AL3 to the cylinder,
piston side. At this time the oil in spring chamber (3) flows port Pa
(Dr) through check valve (E), so the pressure in spring chamber
(3) becomes Pa (Dr). This process prevents cylinder cavitation
during arm in operation

(PB)
BL3
(PA)

AL3

T
F
al3
pa(Dr)

I
H G 1 2 C 3 D E V1004760

Fig.50 When pressure on rod side is high

40
A Check valve H High pressure supply passage
C Spool T Tank passage

Pressure on piston is high [PA > PB ]

When the pressure at AL3 is greater than BL3, check valve A
closes. The pressurized oil acts against piston B, and if it exceeds
the force of spring D, piston B and spool C move right and
passage (2) is opened wide. The return oil now flows through
unrestricted passage (1) and (2) to tank. If servo hydraulic
pressure is applied to port (pa) the force of the servo hydraulic
pressure multiplied by the piston area is added to the spring force
and moves spool C, closing passage (2). As the return oil
pressure rises the regeneration process starts.
When port (Pa) is no-load condition, the oil in spring chamber (3)
flows to port Pa (Dr) through check valve (E), so the pressure in
spring chamber (3) becomes Pa (Dr).

(PB)
BL3
(PA)

AL3

T
al3 F

pa(Dr)

I
H G B 1 2 C 3 D E V1004761

Fig.51 When pressure on piston is high

A Check valve E Check valve I Servo hydraulic oil

B Piston F Arm regenerating valve R Reserve passage
C Spool G Check valve for conflux T Tank passage
D Spring H High pressure supply passage J Arm holding valve

Arm regenerating and arm conflux check valve,

disassembly and assembly
(For assembly, reverse disassembly procedure)

Op. no. 00000

Tools:

41
 7 6 4 2 1

5 3 9 8
V1004762

Fig.52 Arm regenerating and arm conflux check valve

When disassembling, mark each part to make assembling easier.

1 Remove cap (1) and pull out spring (2) and spool (3).
- Tools: Socket wrench, spanner 27 mm
- Tightening torque: 10 kgf·m (72 lbf·ft)
2 2 Remove sleeve (4) and pull out piston (5), spring (6) and
check valve (7).
3
3 Remove cap (8) and pull out piston (9).
- Tools: Socket wrench, spanner 27 mm
- Tightening torque: 4 kgf·m (29 lbf·ft)
5

9 V1004763

Fig.53 Disassembly, arm regenerating and arm

conflux check valve

4 Remove plug (10) from piston (9) and pull out check valve
(11).
- Tools: Allen wrench 4 mm
- Tightening torque: 0.8 kgf·m (6 lbf·ft)

11
10 V1004764

Fig.54 Removal, plug and check valve

Arm parallel conflux valve, disassembly and

assembly
(For assembly, reverse disassembly procedure)

42
 Op. no. 00000

5 1
Tools:
When disassembling, mark each part to make assembling easier.

4 3 2 V1004773

Fig.55 Arm parallel conflux valve

1 Remove cap (1) and pull out spring (2), spring seat (3) and
spool (4).
- Tools: Socket wrench, spanner 30 mm
- Tightening torque: 6 kgf·m (43.3 lbf·ft)
2
2 Remove screw (5) and manifold.
3 - Tools: Allen wrench 6 mm
- Tightening torque: 3 kgf·m (21.7 lbf·ft)

4 V1004774

Fig.56 Removal, spool etc.

Arm parallel conflux check valve, disassembly and

assembly
(For assembly, reverse disassembly procedure)

Op. no. 00000

Tools:
When disassembling, mark each part to make assembling easier.
1 2 3 1 Remove cap (1) and pull out check valve (2) and spring (3).
- Tools: Socket wrench, spanner 30 mm
- Tightening torque: 6 kgf·m (43.3 lbf·ft)

2 V1004775

Fig.57 Disassembly, arm parallel conflux check

valve

Main control valve adjustor, adjusting

1 2

V1162608

Fig.58 Main control valve adjustor

43
 1 Adjusting screw (HEX. 6)
2 Lock nut (HEX. 19)

X1 2pump (Basic delivery status): Open main control valve

adjustor
1 Loosen lock nut and turn adjusting screw counter clockwise (8
rotations) until fully opened (10 mm).
1 V1158513 Tightening torque: 3 ±0.3 Nm (2.2 ±0.2 lbf ft)
Fig.59 Valve is opened 2 Tighten lock nut.
1 10 mm (0.39 inches) Tightening torque: 30 ±3 Nm (22.2 ±0.2 lbf ft)

X1 1pump: Close main control valve adjustor

1 Loosen lock nut and turn adjusting screw clockwise (8
rotations) until fully closed (10 mm).
Tightening torque: 3 ±0.3 Nm (2.2 ±0.2 lbf ft)
1 V1158514 2 Tighten lock nut.
Fig.60 Valve is closed Tightening torque: 30 ±3 Nm (22.2 ±0.2 lbf ft)
1 10 mm (0.39 inches)

Logic valve, description

In neutral and boom lowering

Servo hydraulic signal : OFF
E D C dr5
d1
d2

Pb
F G
a

b
Z
H A

1 B

Z V1004766

Fig.61 Logic valve, in neutral and boom lowering

A Piston F From PL pump (Pa)

B Piston G Boom raise servo hydraulic oil
C Check valve H High pressure supply passage for
D Poppet 3-spool side boom (Pb)
E Orifice

Pistons A and B are positioned as shown by the force of the

springs. Pressure Pa at (a) port flows to chamber Z through
passage (1) and (2) when check valve C opens. Pressure Pb‚ at
(b) port flows to chamber Z from orifice E of poppet D. This
process prevents cylinder cavitation during arm in operation.
In case of Pa > Pb

44
 As area d1 > d2, poppet D remains in position and the passage
between (a) and (b) is cut off. (when the boom is lowered, some
oil is leaked through orifice E).
In case of Pa < Pb
The pressure in chamber Z becomes Pb‚ through orifice E of
poppet D, so check valve C is closed. Poppet D is positioned in
place due to area difference between d1 and d2, and the passage
between (b) and (a) is cut off.

Boom raising
Servo hydraulic signal : ON
When the boom is raised, servo hydraulic pressure is applied to
Pb‚ port. Piston A and B move left, and passage (1) and (2) are
cut off.
In case of Pa > Pb
The pressure in chamber Z becomes Pb through orifice E of
poppet D, so poppet D is opened and oil flows from (a) to (b).
In case of Pa < Pb
E D C dr5
d1
d2

Pb
F G
a

b
Z
H A
B
1

Z
Pa < Pb V1004767

Fig.62 Logic valve, boom raising

A Piston F From PL pump (Pa)

B Piston G Boom raise servo hydraulic oil
C Check valve H High pressure supply passage for
D Poppet 3-spool side boom (Pb)
E Orifice

The pressure in chamber Z becomes Pb through orifice E of

poppet D. Poppet D is positioned and the passage between (a)
and (b) is cut off. This process prevents cylinder cavitation during
arm in operation.

Logic valve, disassembly and assembly

(For assembly, reverse disassembly procedure)

45
 Op. no. 00000

Tools:
When disassembling, mark each part to make assembling easier.
7 6 5 4 3 2 1

10 9 8 V1004768

Fig.63 Logic valve

1 Remove cap (1) and pull out pistons (2, 3) and spring (4).
Pull out sleeve (13) by tapping the left side of cover lightly.
- Tools: Socket wrench, spanner 36 mm
2
- Tightening torque: 10 kgf·m (72.2 lbf·ft)
3

4 V1004769

Fig.64 Removal, spring etc.

2 Pull out sleeve (5) by using the horizontal hole and pull out
spring (6) and check valve (7).

6
7 V1004770

Fig.65 Removal, check valve etc.

10 9 8 3 Insert a round bar with threaded screw (M5 × 0.8) in one end
into sleeve (8) and pull out the sleeve.

M5 x 0.8 V1004771

Fig.66 Removal, sleeve etc.

4 Pull out spring (9) and poppet (10).

10 V1004772

Fig.67 Removal, poppet and spring

46
 Load check valve, disassembly and assembly
(For assembly, reverse disassembly procedure)

Op. no. 00000

1 1
Tools:

2 2
When disassembling, mark each part to make assembling easier.

3 3

A B V1004783

Fig.68 Load check valve

A (Single) Boom, slew
B (Double) Arm, travel, bucket, option

1 Remove cap (1) and pull out spring (2) and spool (3).
- Tools: Socket wrench, spanner 41 mm
3 - Tightening torque: 10 kgf·m (72 lbf·ft)

4
2
V1004784

Fig.69 Removal, spool etc.

Straight travel changeover valve, disassembly and

assembly
(For assembly, reverse disassembly procedure)

Op. no. 00000

1
Tools:
When disassembling, mark each part to make assembling easier.

6 5 4 3 2
V1004776

Fig.70 Straight travel changeover valve

1 Remove cap (1) and pull out spool assembly.

- Tools: Socket wrench, spanner 30 mm
- Tightening torque: 6 kgf·m (43 lbf·ft)
V1004777
2 Hold spool with holder and vise, and loosen nut (2)
Fig.71 Removal, spool assembly - Tools: Spanner, socket wrench 13 mm
- Tightening torque: 1.5 kgf·m (11 lbf·ft)
NOTE!
Tighten nuts prior to assembling.

47
 6 3 Remove nut (2) and pull off spacer (3), spring (4) and spring
seat (5).

2
2
3
4

5 V1004778

Fig.72 Removal, spring etc.

Foot relief valve (flow sensing valve), description

A B C Oil in the center bypass passage flows to tank passage through
orifice C of poppet A. Pump delivery volume can be controlled as
pressure (fp) balanced with the passing flow at orifice C is fed
back to the pump regulator.
(fp) P

T V1004754

Fig.73 Foot relief valve

A Poppet
B Spring
C Orifice
P From center bypass passage
T Tank passage
N Pressure signal to pump

When due to a delayed response of the pump, a large amount of

oil flows, pressure (fp) exceeds the set pressure of spring B, and
poppet A will open and the hydraulic oil flows to tank. Therefore,
it acts as a relief valve.

V1004755

Fig.74 Act as a relief valve

48
 Foot relief valve (flow sensing valve), disassembly
(For assembly, reverse disassembly procedure)

Op. no. 00000

Tools:
When disassembling, mark each part to make assembling easier.
1 2 1 Remove cap (1) and pull out poppet (2).

3 4 5 V1004756

Fig.75 Foot relief valve

2 Remove cap (3) and pull out shim (4) and spring (5).
- Tools: Socket wrench, spanner 30 mm
- Tightening torque: 6 kgf·m (43 lbf·ft)
NOTE!
2 If shims for adjusting pressure are installed, confirm the
1
quantity.

3 V1004757

Fig.76 Removal, poppet etc.

49
 Center bypass valve, disassembly and assembly
(For assembly, reverse disassembly procedure)

Op. no. 00000

1 2 3
Tools:
When disassembling, mark each part to make assembling easier.

V1004779

Fig.77 Center bypass valve

1 Remove cap (1) and pull out spring (2) and spool (3).
- Tools: Socket wrench, spanner 41 mm
- Tightening torque: 10 kgf·m (72 lbf·ft)
NOTE!
2 Note that the spool notches in 3 series and 4 series side are
different.

3 V1004780

Fig.78 Removal, spring

50
 Load check valve – single, disassembly and
assembly
(For assembly, reverse disassembly procedure)

Op. no. 00000

3 Tools:
When disassembling, mark each part to make assembling easier.
2

1
V1004781

Fig.79 Load check valve

1 Remove cap (1) and pull out spring (2) and check valve (3),
(4).
- Tools: Allen wrench 12 mm
- Tightening torque: 20 kgf·m (144 lbf·ft)
3
NOTE!
2
There is no check valve (4) in the boom and slew.
NOTE!
The hole diameter of the cap is different in each assembling
portion, so pay attention during assembly.

1 V1004782

Fig.80 Removal, check valve etc.

Control valve, replacing

Op. no. 912-001

51
 WARNING
Risk of crushing injury.
The hydraulic system could respond slowly at low temperatures
and could cause unexpected machine movements.
Operate carefully until the hydraulic system has reached
operating temperature.

WARNING
Hot hydraulic oil and hydraulic oil under pressure may result in
severe personal injuries

WARNING
Lower the digging units to the ground and stop the engine (start
switch ON position). Operate the control levers several times to
release the remaining pressure in the hydraulic piping.
NOTE!
Draining oil must be collected in a barrel. Plug all hoses/lines and
connections when these have been disconnected or removed.
NOTE!
Any work on the hydraulic system requires great demands on
cleanliness. Even very small particles can cause damage or clog
up the system. therefore, wipe areas clean before any work is
carried out.
1 Place the machine in the Service position B, See 091,
Service position
2 Connect drain hose to drain valve and drain hydraulic oil into
an oil container.
Disconnect drain hose after draining hydraulic oil.

V1161648
1
Fig.81 Hydraulic oil, draining
1 Drain valve

52
 3 Remove screws and cover.

V1161651
1 2
Fig.82 Cover, removal
1 Screws
2 Cover

4 Remove screws and cover.

V1161652
1 2
Fig.83 Cover, removal
1 Screws
2 Cover

5 Open engine hood and remove screws.

V1161659
1
Fig.84 Engine hood, removal
1 Screws

53
 1 6 Remove engine hood with hoist.

V1161660
2
Fig.85 Engine hood, removal
1 Hoist
2 Engine hood

7 Remove screws and main control valve cover.

V1161661
1 2
Fig.86 Cover, removal
1 Screws
2 Cover

8 Remove screws to move air cleaner.

V1161662
1 2 3
Fig.87 Air cleaner, move
1 Screws
2 Bracket
3 Air cleaner

54
 1 2 9 Loosen clamp and disconnect hose.

V1161664
3
Fig.88 Hose, disconnect
1 Clamp
2 Screws
3 Hose

1 2 10 Disconnect hose and wire harness.

Loosen clamp and remove pipe.

V1161665
3
Fig.89 Pipe, removal
1 Hose
2 Wire harness
3 Pipe

1 2 11 Remove screws and set the expansion tank aside.

V1161666
2
Fig.90 Expansion tank, move
1 Expansion tank
2 Screws

55
 1 12 Remove screws and cover.

V1161667
2
Fig.91 Cover, removal
1 Cover
2 Screws

1 13 Disconnect hydraulic servo hoses and set the hoses aside.

Disconnect wire harness.

V1161678

Fig.92 Hoses, disconnecting

1 Hydraulic servo hoses

14 Disconnect hydraulic main hoses and return pipe.

V1161679
1 2 1
Fig.93 Main hoses and return pipe, disconnecting
1 Main hoses
2 Return pipe

56
 1 2 15 Hold main control valve with hoist.

V1161680

Fig.94 Hoist, installation

1 Hoist
2 Main control valve

1 16 Remove mounting screws and lower it to work bench safely.

NOTE!
Tightening torque: 261.8 ±26.5 N m (192.8 ±19.5 lbf ft) (26.7
±2.7 kgf m)
17 Transfer the fittings/elbows and hoses from old main control
valve to new control valve.
NOTE!
When assembling, make sure that the O-ring is installed
before assembling connector and elbow.
Tightening torque See 9121, Main control valve, port size
and tightening torque
V1161681
18 Install a new control valve in reverse order of removal
Fig.95 Main control valve, removal
procedure.
1 Mounting screws
NOTE!
O-rings disassembled should be replaced with new ones.
19 Refill hydraulic oil.
20 Start the engine, test machine and check main relief/port
relief pressure. See : Main relief valve, adjustment page 20
Port relief valve pressure, measuring and adjusting page 26
9121, Main control valve, specifications

57
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To From
Volvo Construction Equipment AB ....................................................................................
Customer Support Division
Dept. 45110, RLA 0301 ....................................................................................
SE-631 85 Eskilstuna
Sweden ....................................................................................
e-mail: servicemanuals@volvo.com

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Ref. no. PUB 20048403-A English
2015.10
Volvo, Pyeongtaek