Hyundai Excavator R210LC-7. Service and repair manual - page 6

2-46

4. TROUBLESHOOTING

GENERAL COMMENTS

When any abnormal phenomenon is noticed, investigate whether it is a failure of the control valve
itself or a problem in the pump proper, pilot pump or circuit.
For this purpose, the pilot pressure, pump discharge pressure, load pressure, etc. should be measured.
Additionally, even when partial disassembly and checking is carried out, follow the previously
mentioned disassembly and assembly procedures.

Since dust is very harmful to hydraulic components, pay full attention to dust prevention. 
Even for partial disassembly dust prevention measures should be carried out.

Handle movable parts carefully.   Even for a small damage, correction using an oilstone should be
carried out.

Carefully carry out your investigation, paying due attention not to damage the sealing faces of
O-rings.   Such damage will cause both internal and external oil leakage.

TROUBLESHOOTING

1)

2)

(1)

(2)

(3)

(4)

Phenomenon

Possible cause

Remedy

Main relief valve malfunctions.

- Dirt is jammed between main

plunger and seat.

- Dirt is jammed between poppet and

seat.

- Main plunger is stuck.
- Spring is broken or fatigued.
- Restriction in main plunger is clogged.
- Adjusting screw is loose.

Orifice just before control valve in pilot
line is clogged.

Clearance between spool and casing
is excessive.

Spool does not return to correct
neutral position.

- Dirt is jammed between casing and

spool, or casing and spool are stuck
together.

- Spring is broken or fatigued.
- Pilot line is clogged with dirt.

Main relief valve malfunctions.

Port relief valve malfunctions.

Lock valve assembly malfunctions.

Lockvalve poppet malfunctions

- Dirt is jammed between poppet and

casing.

- Poppet is stuck.
- Spring is broken or fatigued.

Machine cannot travel or
swing or functions poorly
at low speed(Insufficient
force) or generally
responds slowly.

Cylinder falls significantly
under its own weight when
the spool is in neutral.

Measure pressure of main relief valve.

- Disassemble valve and clean parts.

Replace assembly, if damaged
severely.

- Same as above.

- Correct stuck section with oilstone.
- Remove spring.
- Remove dirt.
- Readjust it and tighten locknut to

specified torque.

Remove dirt.

Replace spool.

Measure secondary pilot pressure.

- Disassemble valve and clean parts.

Correct stuck section with oilstone.

- Replace spring.
- Remove dirt.

Measure pressure of main relief valve.

Measure pressure of main relief valve.

Replace lock valve assembly.

- Disassemble poppet and clean parts

- Correct stuck section with oilstone.
- Replace spring.

2-47

Phenomenon

Possible cause

Remedy

Load check valve malfunctions

- Dirt is jammed between poppet and

casing.

- Poppet is stuck.
- Spring is broken or fatigued.

Main spool malfunctions.

- Clearance between casing and

spool is excessive.

- Dirt is jammed between casing and

spool.

- Spool is stuck.
- Return spring is broken or fatigued.
- Pilot line is clogged with dirt.

Main relief valve malfunctions.

Port relief valve malfunctions.

Each confluence valve malfunctions.

- Spool is stuck.
- Spring is broken or fatigued.
- Clearances between casing A and

casing B and spool are excessive.

Low pressure relief valve malfunctions.

- Dirt is jammed between poppet and

casing.

- Spring is broken or fatigued.
- Restriction in poppet is clogged.

When pilot control lever is
operated for cylinder
hoisting, the cylinder
initially falls.

Bucket, boom and arm
only do not work.
Action is slow(Insufficient
force) or response is slow.

Main boom and arm
confluence does not
function.

Negative control does not
function and minimum
flow cannot be obtained
when lever is in neutral.

- Disassemble poppet and clean parts

- Correct stuck section with oilstone.
- Replace spring.

Disassemble poppet and clean parts

- Replace spool.

- Disassemble valve and clean parts.

- Correct stuck section with oilstone.
- Replace spring.
- Remove dirt.

Measure pressure of main relief valve.

Measure pressure of main relief valve.

Measure pilot pressure.

- Correct stuck section with oilstone.
- Replace spring.
- Replace spool.

Measure pressure of low pressure
relief valve.

- Disassemble valve and clean parts.

Replace assembly, if damaged
severely.

- Replace spring.
- Disassemble valve and clean parts.

Remove dirt.

CONTROL VALVE TROUBLE SHOOTING

2)

2-48

Phenomenon

Possible cause

Remedy

Main plunger or pilot poppet in relief
valve is stuck or remains open, or dirt
is jammed in the seat of valve.

Pilot poppet in relief valve is scored.

Wear due to dirt.

Locknut and adjusting screw are loose.

Seat is scored.
O-ring is worm.

Parts are stuck with dirt.

Pressure does not rise at
all.

Relief pressure is
unstable.

Relief pressure is not
correct.

Oil leakage

Check for dirt that is jammed in the
seat of the valve.
Check if parts slide freely.
Clean all parts thoroughly.

Replace scored parts.
Clean all parts.
Remove score on surface.

Disassemble valve and clean parts.

Adjust pressure.

Replace scored or worm parts.
Check that all parts move smoothly,
before reassembling them.

Check them for scratch, notch or dirt,
before reassembling them.

RELIEF VALVE TROUBLE SHOOTING

3)

2-49

Phenomenon

Possible cause

Remedy

Existence of scratches, rusting or
corrosion.

Existence of scratches, fretting,
rusting or corrosion.

Insert each spool individually into its
respective casing bore, rotate and
reciprocate it.

Damage of poppet or spring.

Insert poppet into casing and move it.

Rusting, corrosion, deformation or
breaking of spring, spring seat, plug
or cover.

External oil leakage.

Rusting, corrosion or deformation of
seal.

External rust or damage.

Contacting face of valve seat.

Contacting face of poppet.

Abnormal spring.

O-rings, back up rings and seals.

Casing

Spool

Poppet

Spring

Seal

Main relief valve,
port relief valve and
negative control relief valve

In case of damage in the following
areas, replace part:
- Sliding sections of casing bore and

spool, especially land sections
continuously seeing pressure.

- Seal pocket section where spool is

inserted.

- Seal section of port where O-ring

contacts.

- Seal section of each relief valve fro

main and port.

- Other defects that may damage

normal functions.

REplace if its outside sliding section
has scratches or other damage.
(Especially on seal contacting section)

Replace if its sliding section has
scratches or other damage.

Correct or replace if the spool does
not move smoothly.

Correct or replace if sealing is
incomplete.

Use only if it can moves smoothly
without being caught.

Replace if there is significant damage.

Correct or replace.

Correct or replace.

Replace

Replace if damaged.

Replace if damaged.

Replace.

100% replacement in general.

MAIN CONTROL VALVE

4)

2-50

Phenomenon

Possible cause

Remedy

Main relief valve malfunctions.

- Dirt is jammed between main

plunger and seat.

- Dirt is jammed between poppet and

seat.

- Main plunger is stuck.
- Spring is broken or fatigued.
- Restriction in main plunger is clogged.
- Adjusting screw is loose.

Orifice just before control valve in pilot
line is clogged.

Clearance between spool and casing
is excessive.

Spool does not return to correct
neutral position.

- Dirt is jammed between casing and

spool, or casing and spool are stuck
together.

- Spring is broken or fatigued.
- Pilot line is clogged with dirt.

Main relief valve malfunctions.

Port relief valve malfunctions.

Lock valve assembly malfunctions.

Lockvalve poppet malfunctions

- Dirt is jammed between poppet and

casing.

- Poppet is stuck.
- Spring is broken or fatigued.

Machine cannot travel or
swing or functions poorly
at low speed(Insufficient
force) or generally
responds slowly.

Cylinder falls significantly
under its own weight when
the spool is in neutral.

Measure pressure of main relief valve.

- Disassemble valve and clean parts.

Replace assembly, if damaged
severely.

- Same as above.

- Correct stuck section with oilstone.
- Remove spring.
- Remove dirt.
- Readjust it and tighten locknut to

specified torque.

Remove dirt.

Replace spool.

Measure secondary pilot pressure.

- Disassemble valve and clean parts.

Correct stuck section with oilstone.

- Replace spring.
- Remove dirt.

Measure pressure of main relief valve.

Measure pressure of main relief valve.

Replace lock valve assembly.

- Disassemble poppet and clean parts

- Correct stuck section with oilstone.
- Replace spring.

2-46

A. SWING DEVICE(T3X150CHB, UP TO #1937)
1. STRUCTURE

Swing device consists swing motor, swing reduction gear.
Swing motor include mechanical parking valve, relief valve, make up valve and time delay valve.

GROUP 3   SWING  DEVICE

Reduction gear

Swing motor Time delay valve

Relief valve

Air vent port

Grease filling port

Swing reduction
gear oil drain port

SH
PG

Dr2

Mu

A

Air vent port

B

GA

GB

SH

PG

Dr2

A

B

Mu

Port

A

B

Dr2

Mu

PG

SH

GA, GB

Port name

Main port

Main port

Drain port

Make up port

Brake release port

Stand by port

Gage port

Port size

PF 3/4

PF 3/4

PF 3/8

PF 1

PF 1/4

PF 1/4

PF 1/4

21072SF03

2-47

SWING MOTOR

1

Inner ring

2

Oil seal

3

Taper roller bearing

4

Backing spring

5

Cam plate

6

Return plate

7

Piston assembly

8

Lining plate

9

Plate

10

O-ring

11

Piston

12

O-ring

13

Spring

14

Parallel pin

15

Piston

16

Cap

17

O-ring

18

Coned disc spring

19

Teflon ring

20

Bushing

21

Balance plate

22

Needle bearing

23

Snap ring

24

Cylinder

25

Housing

26

Collar

27

Plug

28

Snap ring 

29

Bypass valve assembly

30

Back up ring

31

O-ring

32

O-ring

33

Cover

34

Relief assembly

35

O-ring

36

Hexagon socket bolt

37

Time delay valve

38

O-ring

39

O-ring

40

Hexagon socket bolt

41

Check

42

Spring

43

Cap

44

Back up ring

27

4 5 6 7 8

9 10 11 12 13 14

29

30, 31 32 33

40

41

42

43

35, 44

28

26 25 24

39 23

38 22

21 20 19 18

37 36

34

35 16, 17

3

2
1

15

1)

2-48

REDUCTION GEAR

1

Casing

2

Drive shaft

3

Spacer

5

Roller bearing

6

Oil seal

7

Roller bearing

8

Thrust bearing

9

Carrier 2

10

Stop ring

11

Ring gear

12

Knock pin

13

Pinion gear

14

Thrust gear

15

Planet gear 2

16

Pin 2

17

Spring pin

18

Sun gear 2

19

Carrier 1

20

Side plate 1

21

Pin 1

22

Needle cage

23

Bush 2

24

Planet gear 1

25

Lock washer

26

Side plate 3

27

Sun gear 1

28

Stop ring

29

Plug

30

Plug

31

Socket bolt

32

Gauge pipe

33

Gauge bar

34

Cover plate

35

Hexagon socket bolt

36

Lock plate

37

Hexagon socket bolt

38

Stop ring

39

Side plate 2

25 37 36 13

3

35 34 5

2

30 29

6

7

10

9 11 18 19

26 31 28

27

38

1

32

33

8

14 12

23 15 16 21 17 20 24 22 39

2)

2-49

2. FUNCTION

ROTARY PART

When high pressurized oil enters a cylinder through port(a), which is the inlet of balance plate(1),
hydraulic pressure acting on the piston causes axial force F.   The pressure force F works via the
piston(2) upon the return plate(3) which acts upon the swash plate(4) via an hydrostatic bearing.
Force F1 perpendicular to swash plate(4) and force F2 perpendicular to cylinder center.
Being transferred to the cylinder block(5) through piston, force F2 causes rotational moment at
surroundings of cylinder.
Since cylinder block has 9 equidistantly arrayed pistons, rotational torque is transmitted to cylinder
shaft in order by several pistons connected to the inlet port of high pressurized oil.   When the
direction of oil flow is reversed, rotational direction of cylinder is also reversed.   Output torque is
given by the equation.

p

q

F

T =            , q=Z A PCD tan ,  F1 =               , F

2

=F tan , S=PCD tan

2

COS

Where  p : Effective difference of pressure(kgf/cm

2

)

q : Displacement(cc/rev)
T : Output torque(kgf cm)
Z : Piston number(9EA)
A : Piston area(cm

2

)

: Tilting angle of swash plate(degree)

S : Piston stroke(cm)

4

3

2

5

1

F

PCD

a

a

High
pressure oil

High
pressure oil

Low
pressure oil

S

F

2

1)

2-50

MAKE UP VALVE

In the system using this type of motor, there is no counter balance functioning valve and there
happens the case of revolution exceeding hydraulic supply of motor.   To prevent the cavitation
caused by insufficient oil flow there is a make up valve to fill up the oil insufficiency.
A make up valve is provided immediately before the port leading to the hydraulic oil tank to secure
feed pressure required when the hydraulic motor makes a pumping action.   The boost pressure
acts on the hydraulic motor's feed port via the make up valve.
Pressurized oil into the port B, the motor rotate counterclockwise.
If the plunger of MCV moves neutral position, the oil in the motor is drain via left relief valve, the
drain oil run into motor via right make up valve, which prevent the cavitation of motor.

A

B

2)

2-51

1

Body

2

Seat

3

Plunger

4

Spring

5

Adjusting screw

6

Piston

7

Bushing

8

Spring seat

9

Shim

10

O-ring

11

Back up ring

12

O-ring

Construction of relief valve

The valve casing contains two cartridge type relief valves that stop the regular and reverse
rotations of the hydraulic motor.   The relief valves relieve high pressure at start or at stop of swing
motion and can control the relief pressure in two steps, high and low, in order to insure smooth
operation.

Function of relief valve 

Figure illustrates how the pressure acting
on the relief valve is related to its rising
process.   Here is given the function,
referring to the figure following page.

5

6

9

3

11

10

7

8

12

1

4

2

P=pressure,   T=time

P

Ps

P

2

P

1

1

2

3

4

T

RELIEF VALVE

3)

(1)

(2)

2-52

Ports (P,R) at tank pressure.

When hydraulic oil pressure(P A

1

) reaches the preset force(F

SP

) of spring(4), the plunger(3)

moves to the right as shown.
P

1

A

1=

Fsp+Pg A

2

P

A

1

R

A

2

m

h

n

g

4

g

P=P

1

P

1

=

Fsp+Pg A

2

A

1

2-53

The oil flow chamber g via orifice m and n.   When the pressure of chamber g reaches the preset
force(F

SP

) of spring(4), the piston(6) moves left and stop the piston(6) hits the bottom of bushing(7). 

When piston(6) hits the bottom of bushing(7), it stops moving to the left any further.   As the
result, the pressure in chamber(g) equals(Ps).
Ps A

1

=Fsp+Ps A

2

Ps=

Fsp 

A

1

-

A

2 

6

4

m

n

g

7

6

g

P=P

2

P=P

s

2-54

BRAKE SYSTEM

Control valve swing brake system

This is the brake system to stop the swing motion of the excavator during operation.
In this system, the hydraulic circuit is throttled by the swing control valve, and the resistance
created by this throttling works as a brake force to slow down the swing motion.

Mechanical swing parking brake system

The mechanical swing parking brake system is installed to prevent the upper structure from
swinging downhill because of its own weight when the excavator is parked on a slope since it
completely eliminates the hydraulic drift of swing motion while the excavator is on a slop, work can
be done more easily and safely.

Brake assembly

Circumferential rotation of separate
plate(9) is constrained by the groove
located at housing(26).   When housing
is pressed down by brake spring(16)
through lining plate(10), separate
plate(9) and brake piston(12), friction
force occurs there.
Cylinder(25) is constrained by this friction
force and brake acts, while brake
releases when hydraulic force exceeds
spring force.

Work

Deceleration

Stop

MCV A, B opened

MCV A, B throttled

MCV A, B closed

MCV 

MCV 

MCV 

A

B

A

B

A

B

14

12

9

10

25

26

Groove

9

Separate plate

10

Lining plate

12

Brake piston

14

Spring

25

Cylinder

26

Housing

4)

(1)

(2)

2-55

Operating principle

When the swing control lever(1) is set to the swing position, the pilot oil go to the swing control
valve(2) and to S

h

of the time delay valve(3) via the shuttle valve(4), this pressure move

spool(5) to the leftward against the force of the spring(8), so pilot pump charged oil(P

3

) goes to

the chamber G.
This pressure is applied to move the piston(6) to the upward against the force of the spring(9).
Thus, it releases the brake force.

1

Swing control lever

2

Swing control valve(MCV)

3

Time delay valve

4

Shuttle valve

5

Spool

6

Piston

7

Poppet

8

Spring

9

Spring

10

Orifice

11

Spring

12

Pilot pump

9

6

G

3

10

7

P

g

11

D

8

5

S

h

1

12

P

3

2

4

2

a.

2-56

Meantime, the oil pressure of port D balance with the preset force of spring(11), the pressure of
chamber G keeps constant pressure.

b.

1

Swing control lever

2

Swing control valve(MCV)

3

Time delay valve

4

Shuttle valve

5

Spool

6

Piston

7

Poppet

8

Spring

9

Spring

10

Orifice

11

Spring

12

Pilot pump

9

6

G

3

10

7

P

g

11

D

8

5

S

h

1

12

P

3

2

4

2