Takeuchi Hydraulic excavator TB1140 (Serial No. 514400002~). Operator's Manual

TROUBLESHOOTING

SLEWING

Slewing is slow or lacks force.

Within spec

Is the slewing time within

Normal

spec?

Slow

Faulty

Repair or replace the pilot

Check the pilot valve.

valve.

Normal

Faulty

Repair or replace the housing

Check the control valve.

block.

Normal

Pressure too low

Adjust the slew relief

Check the slew pressure.

Adjust to the set pressure.

valve pressure.

Normal

Pressure does not in-

crease.

Repair or replace the relief

valve.

Faulty

Check the check valves

Repair or replace the brake

in the slew brake valve.

valve.

Normal

Faulty

Repair or replace the slew

Check the slew motor.

motor.

Normal

Slew bearing is faulty.

Replace

1. Is the slewing time within spec?

“2. Service data, Performance criteria”

2. Check the pilot valve.

“No slew movement, Check the pilot valve.”

3. Check the control valve.

“No slew movement, Check the control valve.”

4. Check the slew pressure.

“2. Service data, Performance criteria”

5. Check the check valve in the slew brake valve.

”No slew movement, Check the check valve in

the slew brake valve.”

6. Check the slew motor.

“No slew movement, Check the slew motor.”

SLEWING

5D0AS00

TROUBLESHOOTING

SLEWING

Slewing occurs but overrun is large when slewing stops or slewing fails to stop.

Within spec

Is the overrun when slew-

Normal

ing stops within spec?

Out-of-spec

Faulty

Repair or replace the pilot

Check the pilot valve.

valve.

Normal

Faulty

Repair or replace the housing

Check the control valve.

block.

Normal

Faulty

Check the check valve in

Repair or replace the brake

the slew brake valve.

valve.

Normal

Pressure too low

Adjust the slew relief

Check the slew pressure.

Adjust to the set pressure.

valve pressure.

Pressure does not in-

crease.

Repair or replace the relief

valve.

1. Is the overrun when slewing stops within spec?

“2. Service data, Performance criteria”

2. Check the pilot valve.

Check to see if the pilot valve spool returns to the

neutral position when the operation lever (slew) is re-

leased after operation. Disconnect the hose con-

necting the pilot valve and control valve (Pa3, Pb3)

from the control valve, and attach a pressure gauge

to the disconnected hose.

• Read the pressure gauge when the lever (slew) is

released after operation.

• If the pressure is zero, the pilot valve is normal.

SLEWING

5D0AS00

TROUBLESHOOTING

SLEWING

3. Check the control valve.

Check to see if the control valve (slew section) spool

returns to the neutral position when the operation le-

ver (slew) is returned to the neutral position. Discon-

nect the hose connecting the control valve (B3, A3)

and the slew motor from the control valve, and attach

a pressure gauge to the port of the valve.

• Read the pressure gauge when the lever (slew) is

released after operation.

• If the pressure is zero, the control valve is normal.

4. Check the check valve in the slew brake valve.

“No right or left slew movement, Check the

check valve in the slew brake valve.”

5. Check the slew pressure.

“2. Service data, Performance criteria”

SLEWING

5D0AS00

TROUBLESHOOTING

SLEWING

When stopped on a slope, the upper-structure cannot maintain its posture.

Within spec

Is the slew spontaneous

Normal

drop within spec?

Out-of-spec

Pressure too low

Adjust the relief valve

Check the slew pressure.

pressure for the slew

Adjust to the set pressure.

brake valve.

Normal

Pressure does not in-

crease.

Repair or replace the slew re-

lief valve.

Faulty

Repair or replace the slew

Check the slew motor.

motor.

1. Is the slew spontaneous drop within spec?

“2. Service data, Performance criteria”

2. Check the slew pressure.

Measure the pressure at the right and left slew relief

valves.

• If the measured value is within the specifications,

the valve is normal.

“2. Service data, Performance criteria”

3. Check the slew motor.

“No slew movement, Check the slew motor.”

SLEWING

5D0AS00

TROUBLESHOOTING

BOOM 5

BOOM

Boom cylinder does not move.

Check the operation of

Abnormal

Check the main relief valve

actuators other than the

and pump.

boom cylinder.

Normal

Faulty

Repair or replace the pilot

Check the pilot valve.

valve.

Normal

Faulty

Check the control valve.

Repair or replace.

Normal

Problem solved

Test the port relief valve

The port relief valve is

Repair or replace the port re-

with a replacement valve.

faulty.

lief valve.

No change

Faulty

Check the emergency

Replace

shut-off valve.

Normal

Faulty

Repair or replace the boom

Check the boom cylinder.

cylinder.

1. Check the operation of actuators other than the boom

cylinder.

• Check whether only the boom operation is faulty.

If the operation of other actuators is also defective,

see Overall machine.

2. Check the pilot valve.

Disconnect the hose between the pilot valve and

control valve (Pa4, Pb8) from the control valve, and

attach a pressure gauge to the disconnected hose.

• Operate the lever (boom), and measure the pres-

sure.

• The pilot valve is working normally if the pressure

varies between 0 MPa and 3.9 MPa (0 and 566

psi), according to the lever angle.

If the measured pressure is abnormal, replace the pi-

lot valve.

BOOM

5G0AS00

TROUBLESHOOTING

BOOM 5

3. Check the control valve.

Disconnect the cylinder end of each of the hoses (A,

B, C, D) connecting the control valve and boom cyl-

inders, and attach a pressure gauge to each of the

disconnected hoses.

• Operate the lever (boom), and measure the pres-

sure.

Supply pressure: 34.3 MPa (4975 psi)

If the measured pressure is abnormal, replace the

control valve.

4. Test the port relief valve with a replacement valve.

If the boom cylinder is able to operate with a replace-

ment valve taken out from a normal port relief valve

of the arm, then the port relief valve on the boom side

is faulty.

5. Check the emergency shut-off valve.

Note: The emergency shut-off valve (1) allows pres-

sure to be supplied to the cylinder side from

the check valve (2) when the boom is raised,

which enables the boom to be prevented from

being lowered by the check valve (2) even if

some problem arises such as due to damage

in the hose on the downstream side on the low-

er part of the check valve.

When the boom is lowered, pilot pressure for

boom (lower) operation is supplied to the

emergency shut-off valve (1), and the emer-

gency shut-off valve (1) connects together the

cylinder head side and the return side on the

control valve.

BOOM

5G0AS00

TROUBLESHOOTING

BOOM 5

Boom cylinder is slow or lacks force.

Within spec

Is the speed of the boom

Normal

cylinder within spec?

Out-of-spec

Faulty

Repair or replace the pilot

Check the pilot valve.

valve.

Normal

Faulty

Repair or replace the housing

Check the control valve.

block.

Normal

Problem solved

Test the port relief valve

The port relief valve is

Repair or replace the port re-

with a replacement valve.

faulty.

lief valve.

No change

Faulty

Repair or replace the boom

Check the boom cylinder.

cylinder.

1. Is the speed of the boom cylinder within spec?

“2. Service data, Performance criteria”

2. Check the pilot valve.

“Boom, Boom cylinder does not move.”

3. Check the control valve.

“Boom, Boom cylinder does not move.”

4. Test the port relief valve with a replacement valve.

“Boom, Boom cylinder does not move.”

5. Check the boom cylinder.

Check for leakage inside the boom cylinder (1).

a. With the bucket cylinder fully retracted and the

arm cylinder extended slightly from the fully re-

tracted position, lower the bucket tip to the

ground.

BOOM

5G0AS00

TROUBLESHOOTING

BOOM 5

b. Disconnect the hose (A) from the rod end only,

and drain the oil from the piping. Insert a plug (1)

into the disconnected hose.

• Check the right and left cylinders separately,

one at a time. The two hoses should be discon-

nected from the cylinder that is not being

checked during the check of the other cylinder

and each hose fitted with a plug on the end that

was disconnected.

c. Retract the arm cylinder to lift the bucket off the

ground. If oil leaks from the cylinder piping from

which the hose was disconnected and the boom

cylinder rod retracts, the cylinder is leaking inter-

nally. If no oil leaks from the cylinder piping and

the boom cylinder rod retracts, the control valve is

leaking internally.

Check for leakage inside the boom cylinder (2).

a. Set the machine in the posture shown in the fig-

ure.

b. Disconnect the hose (B) from the head end, and

drain the oil from the cylinder piping. Insert a plug

(2) into the disconnected hose.

• Check the right and left cylinders separately,

one at a time. The two hoses should be discon-

nected from the cylinder that is not being

checked during the check of the other cylinder

and each hose fitted with a plug on the end that

was disconnected.

BOOM

5G0AS00

TROUBLESHOOTING

BOOM 5

Spontaneous drop of the boom cylinder is too large.

Is the spontaneous drop

Within spec

of the boom cylinder with-

Normal

in spec?

Out-of-spec

Faulty

Check for leakage inside

Repair or replace the boom

the boom cylinder.

cylinder.

Normal

Problem solved

Test the port relief valve

The port relief valve is

Repair or replace the port re-

with a replacement valve.

faulty.

lief valve.

Normal

Check the control valve.

Replace the housing block.

1. Is the spontaneous drop of the boom cylinder within

spec?

“2. Service data, Performance criteria”

2. Check for leakage inside the boom cylinder.

“Boom, Boom cylinder is slow or lacks force.”

3. Test the port relief valve with a replacement valve.

“Boom, Boom cylinder does not move.”

4. Check the control valve.

“Boom, Boom cylinder does not move.”

BOOM

5G0AS00

TROUBLESHOOTING

ARM 5

ARM

Arm cylinder does not move.

Check the operation of

Abnormal

Check the main relief valve

actuators other than the

and pump.

arm cylinder.

Normal

Faulty

Repair or replace the pilot

Check the pilot valve.

valve.

Normal

Faulty

Check the control valve.

Repair or replace.

Normal

Problem solved

Test the port relief valve

The port relief valve is

Repair or replace the port re-

with a replacement valve.

faulty.

lief valve.

No change

Faulty

Check the emergency

Replace the emergency shut-

shut-off valve.

off valve.

Normal

Faulty

Repair or replace the arm cyl-

Check the arm cylinder.

inder.

1. Check the operation of actuators other than the arm

cylinder.

• Check whether only the arm operation is faulty.

If the operation of other actuators is also defective,

see Overall machine.

2. Check the pilot valve.

Disconnect the hose between the pilot valve and

control valve (Pa5, Pb5) from the control valve, and

attach a pressure gauge to the disconnected hose.

• Operate the lever (arm), and measure the pres-

sure.

• The pilot valve is working normally if the pressure

varies between 0 MPa and 3.9 MPa (0 and 566

psi), according to the lever angle.

If the measured pressure is abnormal, replace the pi-

lot valve.

ARM

5G1AS00

TROUBLESHOOTING

ARM 5

3. Check the control valve.

Disconnect the hose connecting the control valve

and arm cylinder from the pipe, and attach a pres-

sure gauge to the disconnected hose.

• Operate the lever (arm), and measure the pres-

sure.

Supply pressure: 34.3 MPa (4975 psi)

If the measured pressure is abnormal, replace the

control valve.

1 Arm

2 Bucket

4. Test the port relief valve with a replacement valve.

If the arm cylinder is able to operate with a replace-

ment valve taken out from a normal port relief valve

of the boom, then the port relief valve on the arm side

is faulty.

5. Check the emergency shut-off valve.

• Check it in the cylinder extension direction.

a. Disconnect the hose from the emergency shut-off

valve (PIL port), and attach a pressure gauge to

the hose.

Pil

b. Operate the lever (arm), and measure the pres-

sure.

c. The emergency shut-off valve is defective if the

pressure varies between 0 MPa and 3.9 MPa (0

psi and 566 psi), according to the lever angle.

6. Check the arm cylinder.

“4. Disassembly and assembly, Cylinder”

5G0AQ04Z

ARM

5G1AS00

TROUBLESHOOTING

ARM 5

Arm cylinder is slow or lacks force.

Within spec

Is the speed of the arm

Normal

cylinder within spec?

Out-of-spec

Faulty

Repair or replace the pilot

Check the pilot valve.

valve.

Normal

Faulty

Repair or replace the housing

Check the control valve.

block.

Normal

Faulty

Repair or replace the arm cyl-

Check the arm cylinder.

inder.

1. Is the speed of the arm cylinder within spec?

“2. Service data, Performance criteria”

2. Check the pilot valve.

“Arm, Arm cylinder does not move.”

3. Check the control valve.

“Arm, Arm cylinder does not move.”

ARM

5G1AS00

TROUBLESHOOTING

BUCKET

Bucket cylinder does not move or lacks force.

Check the operation of

Abnormal

Check the main relief valve

actuators other than the

and pump.

bucket cylinders.

Normal

Faulty

Repair or replace the pilot

Check the pilot valve.

valve.

Normal

Faulty

Check the control valve.

Repair or replace.

Normal

Problem solved

Test the port relief valve

The port relief valve is

Repair or replace the port re-

with a replacement valve.

faulty.

lief valve.

No change

Faulty

Check the bucket cylin-

Repair or replace the bucket

der.

cylinder.

1. Check the operation of actuators other than the buck-

et cylinder.

• Check whether only the bucket operation is faulty.

If the operation of other actuators is also defective,

see Overall Machine.

2. Check the pilot valve.

Disconnect the hose between the pilot valve and

control valve (Pa7, Pb7) from one of the valves, and

attach a pressure gauge to the disconnected hose.

• Fit the pressure gauge to the section indicated by

the arrow.

• Operate the lever

(bucket), and measure the

pressure.

• The pilot valve is working normally if the pressure

varies between 0 MPa and 3.9 MPa (0 and 566

psi), according to the lever angle.

If the measured pressure is abnormal, replace the pi-

5G2AS01

lot valve.

“Boom, Boom cylinder does not move.”

BUCKET

5G2AS00

TROUBLESHOOTING

BUCKET

3. Check the control valve.

Disconnect the hose connecting the control valve

and bucket cylinder from the pipe, and attach a pres-

sure gauge to the disconnected hose.

• Operate the lever

(bucket), and measure the

pressure.

Supply pressure: 34.3 MPa (4975 psi)

If the measured pressure is abnormal, replace the

control valve.

1 Arm

2 Bucket

4. Test the port relief valve with a replacement valve.

If the bucket cylinder is able to operate with a re-

placement valve taken out from a normal port relief

valve of the arm, then the port relief valve on the

bucket side is faulty.

5. Check the bucket cylinder.

“4. Disassembly and assembly, Cylinder”

BUCKET

5G2AS00

TROUBLESHOOTING

BUCKET

Spontaneous drop of the bucket is too large.

Is the spontaneous drop

Within spec

of the bucket cylinder

Normal

within spec?

Out-of-spec

Faulty

Check for leakage inside

Repair or replace the bucket

the bucket cylinder.

cylinder.

Normal

Oil leaking inside the control

Replace the housing block.

valve.

1. Is the spontaneous drop of the bucket cylinder within

spec?

“2. Service data, Performance criteria”

2. Check the bucket cylinder.

a. Fully extend the bucket cylinder, fully retract the

arm cylinder, and rest the bucket on the ground.

b. Disconnect the two hoses from the cylinder. Insert

plugs (1) into the disconnected hoses and the cyl-

inder piping.

c. Raise the boom and lift the hoe attachment off the

ground. If the bucket drops, the cylinder is faulty.

Otherwise, there is a leak inside the control valve.

BUCKET

5G2AS00

TROUBLESHOOTING

BOOM SWING 5

BOOM SWING

Swing cylinder does not move.

Check the operation of

actuators other than the

swing cylinder.

Normal

Faulty

Repair or replace the pilot

Check the pilot valve.

valve.

Normal

Faulty

Repair or replace the housing

Check the control valve.

block.

Normal

Problem solved

Test the port relief valve

The port relief valve is

Repair or replace the port re-

with a replacement valve.

faulty.

lief valve.

No change

Faulty

Check the swing cylin-

Repair or replace the swing

der.

cylinder.

1. Use the table to check whether only the boom swing

cylinder operation is faulty. If the operation is faulty,

check the main relief valve and the hydraulic pump

(main).

“2. Service data, Performance criteria”

2. Check the pilot valve.

Disconnect the hose between the pilot valve and

control valve (Pra1, Prb1) from the control valve, and

attach a pressure gauge to the disconnected hose.

• Operate the pilot valve (boom swing), and mea-

sure the pressure.

• The pilot valve is working normally if the pressure

varies between 0 MPa and 3.9 MPa (0 and 566

psi), according to the lever angle.

BOOM SWING

5G3AS00

TROUBLESHOOTING

BOOM SWING 5

3. Check the control valve.

Disconnect the hose connecting the control valve

(AR1, BR1) and swing cylinder (R, H) from the cylin-

der end, and attach a pressure gauge to the discon-

nected hose.

• Operate the lever (boom swing), and measure the

pressure.

Supply pressure: 17 MPa (2465psi)

4. Test the port relief valve with a replacement valve.

If the boom swing cylinder is able to operate with a

replacement valve taken out from a port relief valve

of the normal arm, then the port relief valve on the

boom swing side is faulty.

5. Check the swing cylinder

“4. Disassembly and assembly, Cylinders”

BOOM SWING

5G3AS001

TROUBLESHOOTING

BLADE

Blade cylinder does not move or lacks force.

Check the operation of

actuators other than the

blade cylinder.

Normal

Faulty

Repair or replace the pilot

Check the pilot valve.

valve.

Normal

Faulty

Check the control valve.

Repair or replace.

Normal

Problem solved

Test the port relief valve

The port relief valve is

Repair or replace the port re-

with a replacement valve.

faulty.

lief valve.

No change

Faulty

Check the swivel joint.

Repair or replace.

Normal

Faulty

Repair or replace the blade

Check the blade cylinder.

cylinder.

1. Use the table to check whether only the blade cylin-

der operation is faulty. If the blade cylinder is faulty,

check the main relief valve and the hydraulic pump.

“2. Service data, Performance criteria”

Lever to operate

Device to check

2nd auxiliary line

Relief valve R3

Pump Pr

2. Check the pilot valve.

Disconnect the hose between the pilot valve (blade)

and control valve (Pra2, Prb2) from the control valve,

and attach a pressure gauge to the disconnected

hose.

• Operate the pilot valve (blade), and measure the

pressure.

• The pilot valve is working normally if the pressure

varies between 0 MPa and 3.9 MPa (0 and 566

psi), according to the lever angle.

BLADE

5G5AS00

TROUBLESHOOTING

BLADE

3. Check the control valve.

Disconnect the hose connecting the control valve

(blade section) and swivel joint from the control valve

(AR2, BR2), and attach a pressure gauge to the port

of the control valve.

• Operate the pilot valve (blade), and measure the

pressure.

Supply pressure: 23.6 MPa (3423 psi)

4. Test the port relief valve with a replacement valve.

If the blade is able to operate with a replacement

valve taken out from a normal port relief valve of the

2nd auxiliary line, then the port relief valve on the

blade side is faulty.

After the above check is complete, return the port re-

lief valve to its prescribed position.

5. Check the swivel joint.

Disconnect the hose connecting the swivel joint and

blade cylinder from the cylinder. Attach a pressure

gauge to the disconnected hose.

• Fit the pressure gauge to the section indicated by

the arrow.

• Operate the pilot valve (blade), and measure the

pressure.

• The swivel joint is faulty if the measured value list-

ed below is not achieved.

Supply pressure: 23.6 MPa (3423 psi)

5G5AS01

BLADE

5G5AS00

TROUBLESHOOTING

BLADE

The spontaneous drop of the blade is too large, or the blade cannot support the machine.

Within spec

Is the spontaneous drop

Normal

of the blade within spec?

Out-of-spec

Faulty

Check for leakage inside

Repair or replace the housing

the blade cylinder.

block.

Normal

Faulty

Check the swivel joint

Repair or replace the swivel

and control valve.

joint or control valve.

1. Is the spontaneous drop of the blade within spec?

“2. Service data, Performance criteria”

2. Check for leakage inside the blade cylinder.

a. Raise the machine using the hoe attachment, and

fully lower the blade.

b. Disconnect the hose from the rod end of the blade

cylinder (right), and drain oil from the hose.

Insert a plug (1) into the disconnected hose.

• Remove the two hoses from the blade cylinder

(left) not being checked, and insert plugs (1) into

the disconnected ports and hoses.

• After checking the cylinder of the blade cylinder

(right), check the blade cylinder (left).

BLADE

5G5AS00

TROUBLESHOOTING

BLADE

c. Raise the boom to apply a load to the blade.

• If the machine drops while the oil drains from

the cylinder piping, the cylinder is faulty.

If the machine drops even though no oil drains

out, the control valve or the swivel joint is faulty.

If the machine cannot be supported by the

blade, replace the port relief valve with a nor-

mal valve. If the blade can now support the ma-

chine, the port relief valve was faulty.

5G5AF05Z

3. Check the swivel joint and control valve.

Disconnect the control valve end of the hose con-

necting the swivel joint and control valve. Insert a

plug in the disconnected hose.

Follow the procedure in item 2 a to c above to apply

a load to the blade.

If the machine drops, the swivel joint is faulty.

If the machine does not drop, oil is leaking inside the

control valve.

BLADE

5G5AS00

TROUBLESHOOTING

AUXILIARY HYDRAULICS

Prescribed pressure is not supplied to the 1st and 2nd auxiliary lines.

Check the operation of

actuators other than the

auxiliary line.

Normal

Check the voltage sup-

Faulty

plied to the proportional

Repair or replace.

control solenoid valve.

Normal

Faulty

Check the proportional

Repair or replace.

control solenoid valve.

Normal

Faulty

Repair or replace the housing

Check the control valve.

block.

1. Use the table to check whether only the auxiliary line

operation is faulty. If operation is faulty, check the

main relief valve and the hydraulic pump.

“2. Service data, Performance criteria”

1st auxiliary line

Lever to operate

Device to check

Right travel

Relief valve R1

Pump P1

2nd auxiliary line

Lever to operate

Device to check

Dozer blade

Relief valve R3

Pump P4

AUXILIARY HYDRAULICS

5G6AS00

TROUBLESHOOTING

AUXILIARY HYDRAULICS

2. Check the voltage supplied to the proportional control

solenoid valve.

Operate the pilot valve proportional lever, and check

the voltage supplied to the proportional control sole-

noid valve from the proportional amplifier.

<1st auxiliary line>

• Terminals (1) and (2), Marking A

• Terminals (3) and (4), Marking B

24 V is normal.

<2nd auxiliary line>

• Terminals (5) and (6), Marking C

• Terminals (7) and (8), Marking D

24 V is normal.

5G6AS02

3. Check the proportional control solenoid valve.

<1st auxiliary line>

Disconnect the hose between the proportional con-

trol solenoid valve (1) and control valve (2), (Pa3,

Pb3) from the control valve, and attach a pressure

gauge to the disconnected hose.

• Operate the proportional lever for the pilot valve,

and measure the pressure.

• The pilot valve is working normally if the pressure

varies between 0 MPa and 3.9 MPa (0 and 566

psi), according to the lever angle.

<2nd auxiliary line>

Disconnect the hose between the proportional con-

trol solenoid valve (3) and control valve (Pra3, Prb3)

from the control valve, and attach a pressure gauge

to the disconnected hose.

• Operate the proportional lever for the pilot valve,

and measure the pressure.

• The pilot valve is working normally if the pressure

varies between 0 MPa and 3.9 MPa (0 and 566

psi), according to the lever angle.

AUXILIARY HYDRAULICS

5G6AS00

TROUBLESHOOTING

AUXILIARY HYDRAULICS

4. Check the control valve.

AR3

<1st auxiliary line>

BR3

Disconnect the auxiliary line hose from the control

valve (A2, B2), and attach a pressure gauge to the

AR1

port on the control valve.

• Operate the proportional lever for the pilot valve,

BR1

and measure the pressure.

• Supply pressure: 34.3 MPa (4975 psi)

<2nd auxiliary line>

Disconnect the auxiliary line hose from the control

valve, and attach a pressure gauge to the port on the

control valve (AR3, BR3).

• Operate the proportional lever for the pilot valve,

and measure the pressure.

• Supply pressure: 34.3 MPa (4975 psi)

AUXILIARY HYDRAULICS

5G6AS00

TROUBLESHOOTING

PISTON PUMP

Symptoms

Major causes

Remedies

Noise is too loud, unusual

•

Suction hose is crushed or suction filter

•

Remove the dirt and correct the crushing.

sound is heard

is clogged.

•

Joint in the suction side is loose and

•

Retighten each joint.

sucking air.

•

Cavitation is being produced due to too

•

Replace with hydraulic oil of proper viscos-

high viscosity of the hydraulic oil.

ity.

•

Pump and engine are not center

•

Center them again.

aligned.

•

Frothing of hydraulic oil.

•

Investigate the cause of frothing and cor-

rect it.

•

Engine RPM is too high.

•

Run at the rated RPM.

•

Mechanical damage to the parts (e.g.,

•

Replace the damaged part(s) or the pump.

bearing).

•

The regulator is experiencing hunting

•

Repair the regulator.

oscillation.

Discharge is insufficient

•

Engine RPM is too low.

•

Run at the rated RPM.

•

Oil temperature is too high.

•

Stop running, and check the temperature

again after the oil cools down.

•

Viscosity of hydraulic oil is too high.

•

Replace with hydraulic oil of proper viscos-

ity.

•

Pump volume efficiency becomes low.

•

Replace the pump.

•

Hydraulic oil tank level is too low.

•

Add oil to the specified level.

•

Clogging in the suction piping or the

•

Clean the piping.

suction filter.

•

Leak volume of hydraulic devices other

•

Repair or replace the leaking hydraulic de-

than the pump is increased.

vice.

•

The regulator is faulty.

•

Repair the regulator.

Pressure is not increased

•

Set pressure for the relief valve drops.

•

Set the relief valve pressure again.

•

Leak volume of hydraulic devices other

•

Repair or replace the leaking hydraulic de-

than the pump is increased.

vice.

•

Pump volume efficiency becomes low.

•

Replace the pump.

Abnormal heat is generat-

•

Leak volume from the pump is in-

•

Replace the pump.

creased.

•

Mechanical damage to the parts (e.g.,

•

Replace the damaged part(s) or the pump.

bearing).

•

Seizing on the sliding part.

•

Replace the damaged part(s) or the pump.

Oil leak

•

Seals are damaged.

•

Replace the seal(s).

•

Sliding part between the shaft and the

•

Replace the shaft or the pump.

oil seal is worn out.

•

Plugs and bolts are loosened.

•

Retighten the plugs and bolts, or replace

the seals.

PISTON PUMP

5I0AS00

TROUBLESHOOTING

GEAR PUMP 5

GEAR PUMP

“4. Disassembly and assembly, Gear pump”

Symptoms

Major causes

Remedies

No discharging operation

•

Direction of rotation is incorrect.

•

Rotate in the rated direction.

•

Hydraulic oil tank level is too low.

•

Add oil to the specified level.

•

Clogging in the suction piping or the

•

Clean the piping.

suction filter.

•

Viscosity of hydraulic oil is too high.

•

Replace with hydraulic oil of proper viscos-

ity.

•

RPM is too low.

•

Run at the rated RPM.

Noise is too loud, unusual

•

Cavitation is being produced due to the

•

Remove the dirt and correct the crushing.

sound is heard

crushed hose or clogged filter of the

suction side.

•

Joint in the suction side is loose and

•

Retighten each joint.

sucking air.

•

Cavitation is being produced due to too

•

Replace with hydraulic oil of proper viscos-

high viscosity of the hydraulic oil.

ity.

•

Pump and engine are not center

•

Center them again.

aligned.

•

Frothing of hydraulic oil.

•

Investigate the cause of frothing and cor-

rect it.

•

Oil seal is deformed, worn out or dam-

•

Replace the oil seal.

Oil leak from the oil seal

aged.

Oil leak from the mating

•

Body seal is damaged, or the sliding

•

Replace with a new one.

surface between the

part is worn out.

housing and the flange or

housing and the cover

Discharge is insufficient

•

Bushing seal is damaged.

•

Replace the bushing seal.

•

Cavitation is being produced.

•

Clean the suction filter and the suction pip-

ing.

•

Aeration is being produced.

•

Check if piping is properly screwed in.

•

Viscosity of hydraulic oil is too low.

•

Replace with hydraulic oil of proper viscos-

ity.

GEAR PUMP

5I1AQ00

TROUBLESHOOTING

CONTROL VALVE

“4. Disassembly and assembly, Control valve”

The problems are listed individually in the table below, but in reality, many problems have multiple causes. Therefore,

try to check and eliminate each possible cause one at a time.

Symptoms

Major causes

Remedies

Oil leak from the spool

•

Flaw is on the sealing part or the seal lip

•

Replace with a new one.

seal

is worn out due to prolonged use.

•

Flaw (e.g., dents or scratches) on the

•

Repair or replace the spool.

sliding part of the spool seal is caused

by an external factor.

•

The lid that is pushing the sealing parts

•

Correct the lid, and determine the partial

in place is installed improperly (lid is

wear degree of the seal.

distorted)

•

Old paint remains on the seal sliding

•

Remove it by using thinner or mechanical

part of the spool.

force. When removing, take care not to

damage the spool surface or the seal lip.

•

Tank pressure becomes too high for the

•

Remove the cause of the flow resistance.

performance of the sealing material.

Sliding part of the spool is

•

Foreign matter is caught in the sliding

•

Overhaul and repair or replace.

not smooth

part of the spool.

•

Oil film between the spool and the body

•

Try to decrease the oil temperature. If the

becomes too thin due to the increased

relief valve is started often, find the cause

oil temperature.

and correct it.

•

Lubrication is disabled due to deterio-

•

Oil should be replaced. The circuit also

rated oil.

should be overhauled in some cases.

•

Spool is worn out because of prolonged

•

Replace the spool and the valve block as-

use or of the unbalanced force applied.

sembly.

•

Spool is bent by the external force.

•

Check for the straightness of the spool, and

repair or replace.

•

Whole valve is distorted due to the dis-

•

Check the distortion, independent of the in-

tortion of the installation surface.

stallation surface (loosening the bolts will

help).

•

Valve is operated with the pressure or

•

For pressure, measure it with a pressure

the flow rate of out-of-spec.

gauge. For flow rate, determine it by finding

out the movement speed and capacity of

the actuator.

•

Fixing bolts are over-tightened.

•

Check if the fixing bolts are tightened with

the specified torque. If not, tighten them

again with the specified torque.

•

Oil stays in the lid (spring or detent) op-

•

Oil may come out from the lid, if it is leaking

posite to the spool operation.

in the seal of the spool. If that is the case,

replace the seal.

When the actuator is be-

•

Foreign matter is caught in the seat on

•

Disassemble the valve and overhaul or re-

ing raised, it drops once

the load check valve, or the seat is

place the faulty part(s).

damaged by large foreign matter.

CONTROL VALVE

5J0AQ00

TROUBLESHOOTING

CONTROL VALVE

Symptoms

Major causes

Remedies

Spool’s neutral position

•

There are cases of a large oil leak in-

•

Check if the cylinder drops spontaneously

cannot be maintained

side the cylinder.

when it is held. If the cylinder is faulty, dis-

(cylinder drops)

assemble and repair it.

•

Since the clearance between the spool

•

Replace the spool and the valve block as-

and the body is too large, oil is leaking

sembly.

from the clearance.

•

Spool is not completely back in the neu-

•

Manual: Check if the link mechanism is in-

tral position.

terfering with others.

Hydraulic operation: Check the pilot pres-

sure.

•

Foreign matter is caught in the seat of

•

Disassemble, overhaul or replace.

the port relief valve or of the anti-cavita-

tion valve, and thus the oil is bypassing

the section. Or the seat is damaged.

Load cannot be moved

•

Foreign matter is caught in the seat of

•

Disassemble, overhaul or replace.

(pressure cannot be in-

the port relief valve, and thus the oil is

creased)

bypassing the section. Or the seat is

damaged.

•

Adjuster screw on the relief valve is

•

Screw in the adjuster screw. If loose, set the

loose.

adjustment again and fasten with a lock nut.

•

Foreign matter is caught in the seat of

•

Disassemble, overhaul or replace.

the port relief valve or of the anti-cavita-

tion valve, and thus the oil is bypassing

the section. Or the seat is damaged.

•

Spool stroke is out-of-spec.

•

Manual: Check if the link mechanism is in-

terfering with others. Check if the pin or pin

hole on the linking section is worn out.

•

Oil supply from the pump is insufficient,

•

Hydraulic operation: Check the pilot pres-

because the pump is damaged.

sure.

Check for any abnormality in the pump.

If the pump is faulty, replace it and find the

cause of the abnormality (e.g., faulty air

sucking or oil degradation).

Load cannot be moved

•

Overloading

•

Compare with a one with standard load.

(pressure is being in-

•

Mechanical resistance of related parts/

•

Check and add oil, modify or repair the

creased)

devices

(unrelated to the hydraulic

parts/devices.

pressure of the hydraulic oil) is large.

•

Large resistance is generated, be-

•

Repair if the location of clogging or bent is

cause the circuit is clogged with large

known.

foreign matter or the piping is bent.

•

Spool stroke is out-of-spec.

•

Check if the link mechanism is interfering

with others and if the pin or pin hole on the

linking section is worn out.

CONTROL VALVE

5J0AQ00

TROUBLESHOOTING

PILOT VALVE

“4. Disassembly and assembly, Pilot valve”

Symptoms

Major causes

Remedies

The secondary pressure

• Primary pressure is insufficient.

• Keep the primary pressure.

is too low

• The spring is broken or worn out.

• Replace

• The clearance between the spool and

• Replace the spool and the casing assem-

the casing is too large.

bly.

• Too much play in the handle.

• Disassemble and assemble or replace.

The secondary pressure

• The sliding part is not smooth.

• Repair or replace.

is unstable

• The tank line pressure fluctuates.

• Remove the faulty part(s) in the tank line.

• Air is present in the piping.

• Bleed air by operating the valve several

times.

The secondary pressure

• Pressure in the tank line is high.

• Remove the faulty part(s) in the tank line.

is high

• The sliding part is not smooth.

• Repair or replace.

PILOT VALVE

5K2AQ00

TROUBLESHOOTING

SOLENOID VALVE

“4. Disassembly and assembly, solenoid valve”

Symptoms

Major causes

Remedies

Solenoid valve does not

• Wiring short-circuit or wire break.

• Replace

operate

• Coil assembly short-circuit or wire

• Replace

break.

• Foreign matter is caught in the spool.

• Overhaul and repair or replace.

• Damage on the outer circumference of

• Overhaul and repair or replace.

the spool.

• Proportional controller is faulty.

• Repair or replace.

• Primary pressure is insufficient.

• Keep the primary pressure.

Oil leakage from solenoid

• O-ring is damaged.

• Replace

valve

• Seal nut is damaged.

• Replace

SOLENOID VALVE

5K6AQ00

Takeuchi Hydraulic excavator TB1140 (Serial No. 514400002~). Operator's Manual - page 11