Content .. 15 16 17 18 ..

Takeuchi Mini Excavator TB215R (No.215000003~). Operator's Manual - page 17

TROUBLESHOOTING

DOZER BLADE

5G5AX001

DOZER BLADE

Dozer blade cylinder does not move or lacks force.

1. Check the operation of actuators other than of the

dozer blade cylinder.

Determine if only the dozer blade cylinder is faulty by
checking the operation of actuators for the devices
listed in the table on the right. If one of them is faulty,
check the main relief valve and the hydraulic pump
(main).

“5. Troubleshooting, Overall machine, All sys-
tems working, but insufficient force”

2. Check the spool operation.

“5. Troubleshooting, Boom swing, Swing cylin-
der does not move, 2. Check the spool opera-
tion”

3. Check the linkage.

“5. Troubleshooting, Boom swing, Swing cylin-
der does not move, 3. Check the linkage”

Check the operation of
actuators other than of
the dozer blade cylinder.

Normal

Check the spool opera-
tion.

Faulty

Repair or replace the housing
block.

Normal

Check the linkage.

Faulty

Adjust, repair or replace.

Normal

Check the supply pres-
sure of the control valve.

Faulty

Repair or replace the housing
block.

Normal

Check the swivel joint.

Faulty

Repair or replace the swivel
joint.

Normal

Dozer blade cylinder is faulty.

Faulty

Repair or replace the dozer
blade cylinder.

Lever to operate

Device to check

Relief valve

Pump

Slew

TROUBLESHOOTING

DOZER BLADE

5G5AX001

4. Check the supply pressure of the control valve.

Disconnect one of the hoses connected to the con-
trol valve housing block (blade). Fit the pressure
gauge to the hose just disconnected. Operate the le-
ver (blade) and check the supply pressure of the
valve.

• If the value indicated is not as below, the housing

block is faulty.
Supply pressure: 20.0 MPa (2900 PSI)

When only “Dozer Blade Lower” is impossible

• Replace the port relief valve in question with a

port relief valve used for a normal arm. If the dozer
blade cylinder operates normally with the re-
placement valve, the port relief valve used on the
dozer blade side is faulty.

5. Check the swivel joint.

a. nspect the spool stroke “A” of the selector on the

swivel joint, and check if the spool is correctly
switched to the blade side.
• Spool stroke “A”......6 mm (0.2 in.)

b. Disconnect the hose between the swivel joint and

the blade cylinder from the cylinder side. Install a
pressure gauge on the hose just disconnected
and operate the lever (blade).
• If the value indicated is different from the value

given below, the swivel joint is faulty.
Supply pressure: 20.0 MPa (2900 PSI)

TROUBLESHOOTING

DOZER BLADE

5G5AX001

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

1. Is the spontaneous drop of the dozer blade within

specs?

“2. Service data, Performance criteria”

2. Check for leakage inside the dozer blade cylinder.

a. Using the hoe attachments, raise the machine,

then lower the blade fully.

b. Disconnect the hose from the rod side of the doz-

er blade cylinder and drain oil from the piping.
Install the plug (1) on the hose just disconnected.

Is the spontaneous drop
of the dozer blade within
specs?

Within specs

Normal

Out-of-specs

Check for leakage inside
the dozer blade cylinder.

Faulty

Repair or replace the housing
block.

Normal

Inspect the swivel joint
and the control valve.

Faulty

Repair or replace the swivel
joint or control valve.

5G5AF04Z

TROUBLESHOOTING

DOZER BLADE

5G5AX001

c. Raise the dozer boom and apply a load on the

blade.
• If the machine drops while oil drains from the

cylinder’s 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, try replacing the port relief valve with a
normal one. If the blade can support the ma-
chine after this replacement, then the port relief
valve is faulty.

3. Inspect the swivel joint and the control valve.

Disconnect the hose connecting the swivel joint and
control valve from the control valve. Insert a plug into
the hose just disconnected.
Apply a load to the blade by following the steps 2 (a)
through (c) above.
If the machine drops, the swivel joint is faulty.
If the machine does not drop, there is a leak inside
the control valve.

5G5AF05Z

auxiliary hyDraulicS (1ST)

TroubleshooTing

5g6AX001

AUXILIARy hyDRAULICS (1ST)

check the operation of
actuators other than the
auxiliary lines

normal

check the spool opera-
tion

Faulty

Repair or replace the housing

block

normal

Check the linkage

Faulty

Adjust, repair or replace

normal

check the supply pres-
sure of the control valve

Faulty

Repair or replace the housing

block

1. check the operation of actuators other than the

auxiliary lines.

Determine if only the auxiliary lines is faulty by checking

the operation of actuators for the devices listed in the

table on the right. If one of them is faulty, check the
main relief valve and the hydraulic pump (main).

“5. Troubleshooting, Overall machine, All systems

working, but insufficient force”

2. check the spool operation.

“5. Troubleshooting, Traveling, Right or left travel is

impossible, 2. check the spool operation”

3. check the linkage.

“5. Troubleshooting, Traveling, Right or left travel is

impossible, 3. Check the linkage”

4. check the supply pressure of the control valve.

Disconnect one of the hoses connected to the control

valve housing block (1st auxiliary lines). Fit the pressure
gauge to the hose just disconnected. Operate the lever
(1st auxiliary lines) and check the supply pressure of

the valve.

• If the value indicated is not as below, the housing

block is faulty.

Supply pressure:

.0 MPa (

3046

PSI)

auxiliary hyDraulicS (1ST)

Prescribed pressure is not supplied to the auxiliary lines.

lever to operate

Device to check

relief valve

Pump

Swing

SPanner

TroubleshooTing

5g8AX001

SPANNER

Spanner

Spanner cylinder does not move or lacks force

check the operation of
actuators other than the
spanner cylinder

normal

check the spool opera-
tion

Faulty

Repair or replace the housing

block

normal

Check the linkage

Faulty

Adjust, repair or replace

normal

check the supply pres-
sure of the control valve

Faulty

Repair or replace the housing

block

normal

check the swivel joint

Faulty

repair or replace the swivel
joint

normal

spanner cylinder is faulty

repair or replace the spanner
cylinder

Switching between the blade cylinder operation and the
spanner cylinder operation can be done by operating the
lever. Therefore, checking procedure for the spanner cylin

der is similar to that for the blade cylinder.

“5. Troubleshooting, Dozer blade”

1. check the operation of actuators other than the

spanner cylinder.

2. check the spool operation.

“5. Troubleshooting, Traveling, Right or left travel is

impossible, 2. check the spool operation”

3. check the linkage.

“5. Troubleshooting, Traveling, Right or left travel is

impossible, 3. Check the linkage”

4. check the supply pressure of the control valve.

Disconnect one of the hoses connected to the control

valve housing block (spanner). Fit the pressure gauge
to the hose just disconnected. Operate the lever (span

ner) and check the supply pressure of the valve.
• If the value indicated is not as below, the housing

block is faulty.

Supply pressure:

.0 MPa (

2900

PSI)

SPanner

TroubleshooTing

5g8AX001

SPANNER

5. check the swivel joint

a. inspect the spool stroke “A” of the selector on

the swivel joint, and check if the spool is correctly
switched to the blade side.

• Spool stroke “A”......6 mm (0.2 in.)

b. Disconnect the hose between the swivel joint and

the spanner cylinder from the cylinder side. install a

pressure gauge on the hose just disconnected and
operate the lever (spanner).
• If the value indicated is different from the value

given below, the swivel joint is faulty.

Supply pressure:

.0 MPa (

2900

PSI)

TROUBLESHOOTING

PISTON PUMP

5I0AQ00

PISTON PUMP

Symptoms

Major causes

Remedies

Noise is too loud, unusual
sound is heard

• Suction hose is crushed or suction filter

is clogged.

• Remove the dirt and correct the crushing.

• Joint in the suction side is loose and

sucking air.

• Retighten each joint.

• Cavitation is being produced due to too

high viscosity of the hydraulic oil.

• Replace with hydraulic oil of proper viscos-

ity.

• Pump and engine are not center

aligned.

• Center them again.

• 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.,

bearing).

• Replace the damaged part(s) or the pump.

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

suction filter.

• Clean the piping.

• Leak volume of hydraulic devices other

than the pump is increased.

• Repair or replace the leaking hydraulic de-

vice.

Pressure is not increased • Set pressure for the relief valve drops. • Set the relief valve pressure again.

• Leak volume of hydraulic devices other

than the pump is increased.

• Repair or replace the leaking hydraulic de-

vice.

• Pump volume efficiency becomes low. • Replace the pump.

Abnormal heat is generat-
ed

• Leak volume from the pump is in-

creased.

• Replace the pump.

• Mechanical damage to the parts (e.g.,

bearing).

• Replace the damaged part(s) or the pump.

• 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

oil seal is worn out.

• Replace the shaft or the pump.

• Plugs and bolts are loosened.

• Retighten the plugs and bolts, or replace

the seals.

TROUBLESHOOTING

GEAR PUMP

5I1AQ00

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

suction filter.

• Clean the piping.

• 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
sound is heard

• Cavitation is being produced due to the

crushed hose or clogged filter of the
suction side.

• Remove the dirt and correct the crushing.

• Joint in the suction side is loose and

sucking air.

• Retighten each joint.

• Cavitation is being produced due to too

high viscosity of the hydraulic oil.

• Replace with hydraulic oil of proper viscos-

ity.

• Pump and engine are not center

aligned.

• Center them again.

• Frothing of hydraulic oil.

• Investigate the cause of frothing and cor-

rect it.

Oil leak from the oil seal

• Oil seal is deformed, worn out or dam-

aged.

• Replace the oil seal.

Oil leak from the mating
surface between the
housing and the flange or
housing and the cover

• Body seal is damaged, or the sliding

part is worn out.

• Replace with a new one.

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.

TROUBLESHOOTING

CONTROL VALVE

5J0AQ00

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
seal

• Flaw is on the sealing part or the seal lip

is worn out due to prolonged use.

• Replace with a new one.

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

sliding part of the spool seal is caused
by an external factor.

• Repair or replace the spool.

• The lid that is pushing the sealing parts

in place is installed improperly (lid is
distorted)

• Correct the lid, and determine the partial

wear degree of the seal.

• Old paint remains on the seal sliding

part of the spool.

• Remove it by using thinner or mechanical

force. When removing, take care not to
damage the spool surface or the seal lip.

• Tank pressure becomes too high for the

performance of the sealing material.

• Remove the cause of the flow resistance.

Sliding part of the spool is
not smooth

• Foreign matter is caught in the sliding

part of the spool.

• Overhaul and repair or replace.

• Oil film between the spool and the body

becomes too thin due to the increased
oil temperature.

• Try to decrease the oil temperature. If the

relief valve is started often, find the cause
and correct it.

• Lubrication is disabled due to deterio-

rated oil.

• Oil should be replaced. The circuit also

should be overhauled in some cases.

• Spool is worn out because of prolonged

use or of the unbalanced force applied.

• Replace the spool and the valve block as-

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-

tortion of the installation surface.

• Check the distortion, independent of the in-

stallation surface (loosening the bolts will
help).

• Valve is operated with the pressure or

the flow rate of out-of-spec.

• For pressure, measure it with a pressure

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-

posite to the spool operation.

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

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

When the actuator is be-
ing raised, it drops once

• Foreign matter is caught in the seat on

the load check valve, or the seat is
damaged by large foreign matter.

• Disassemble the valve and overhaul or re-

place the faulty part(s).

TROUBLESHOOTING

CONTROL VALVE

5J0AQ00

Symptoms

Major causes

Remedies

Spool’s neutral position
cannot be maintained
(cylinder drops)

• There are cases of a large oil leak in-

side the cylinder.

• Check if the cylinder drops spontaneously

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

• Since the clearance between the spool

and the body is too large, oil is leaking
from the clearance.

• Replace the spool and the valve block as-

sembly.

• Spool is not completely back in the neu-

tral position.

• Manual: Check if the link mechanism is in-

terfering with others.
Hydraulic operation: Check the pilot pres-
sure.

• Foreign matter is caught in the seat of

the port relief valve or of the anti-cavita-
tion valve, and thus the oil is bypassing
the section. Or the seat is damaged.

• Disassemble, overhaul or replace.

Load cannot be moved
(pressure cannot be in-
creased)

• Foreign matter is caught in the seat of

the port relief valve, and thus the oil is
bypassing the section. Or the seat is
damaged.

• Disassemble, overhaul or replace.

• Adjuster screw on the relief valve is

loose.

• Screw in the adjuster screw. If loose, set the

adjustment again and fasten with a lock nut.

• Foreign matter is caught in the seat of

the port relief valve or of the anti-cavita-
tion valve, and thus the oil is bypassing
the section. Or the seat is damaged.

• Disassemble, overhaul or replace.

• 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,

because the pump is damaged.

• Hydraulic operation: Check the pilot pres-

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
(pressure is being in-
creased)

• Overloading

• Compare with a one with standard load.

• Mechanical resistance of related parts/

devices (unrelated to the hydraulic
pressure of the hydraulic oil) is large.

• Check and add oil, modify or repair the

parts/devices.

• Large resistance is generated, be-

cause the circuit is clogged with large
foreign matter or the piping is bent.

• Repair if the location of clogging or bent is

known.

• 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.

TROUBLESHOOTING

PILOT VALVE

5K2AQ00

PILOT VALVE

“4. Disassembly and assembly, Pilot valve”

Symptoms

Major causes

Remedies

The secondary pressure
is too low

• Primary pressure is insufficient.

• Keep the primary pressure.

• The spring is broken or worn out.

• Replace

• The clearance between the spool and

the casing is too large.

• Replace the spool and the casing assem-

bly.

• Too much play in the handle.

• Disassemble and assemble or replace.

The secondary pressure
is unstable

• The sliding part is not smooth.

• Repair or replace.

• 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
is high

• Pressure in the tank line is high.

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

• The sliding part is not smooth.

• Repair or replace.

TROUBLESHOOTING

SOLENOID VALVE

5K6AQ00

SOLENOID VALVE

“4. Disassembly and assembly, solenoid valve”

Symptoms

Major causes

Remedies

Solenoid valve does not
operate

• Wiring short-circuit or wire break.

• Replace

• Coil assembly short-circuit or wire

break.

• Replace

• Foreign matter is caught in the spool.

• Overhaul and repair or replace.

• Damage on the outer circumference of

the spool.

• Overhaul and repair or replace.

• Proportional controller is faulty.

• Repair or replace.

• Primary pressure is insufficient.

• Keep the primary pressure.

Oil leakage from solenoid
valve

• O-ring is damaged.

• Replace

• Seal nut is damaged.

• Replace

TROUBLESHOOTING

CYLINDERS

5L0AQ00

CYLINDERS

“4. Disassembly and assembly, Cylinders”

Symptoms

Major causes

Remedies

Oil is leaking from the pis-
ton rod sliding surface (oil
forms a ring on the piston
rod, which becomes larg-
er and starts dripping)

• Foreign matter is trapped in the inside

diameter of the rod packing or dust
seal.

• Remove the foreign matter.

• Scratching or abnormality of the inter-

nal lip surface of the rod packing or
dust seal.

• Replace the faulty part(s).

• Scratching on the sliding surface of the

piston rod.

• Smooth the sliding surface with an oilstone

(1.6 S or less).

• If the leak persists after smoothing the slid-

ing surface, replace the rod packing and
other seals.

• If the leak persists after replacing the seals,

replace the piston rod.

• Peeling of the hard chromium plated

surface.

• Re-plate the hard chromium plating.

Oil leaking around the rod
cover.

• O-ring is damaged.

• Replace the faulty part(s).

• Backup ring is damaged.

• Replace the faulty part(s).

Oil leaking from welded
joint.

• Tube welding is damaged.

• Replace the faulty part(s).

Spontaneous cylinder
drop (“Spontaneous
drop” is defined as 0.5
mm or greater piston
movement in 10 minutes
when a static load is exert-
ed on the rod. The static
load is determined by
multiplying the maximum
operating pressure by the
cylinder area.)

• Foreign matter is trapped in the wear

ring sliding surface.

• Remove the foreign matter.

• Scratching or abnormality of the wear

ring sliding surface.

• Replace the faulty part(s).

• Scratching on the piston packing slid-

ing surface.

• Replace the faulty part(s).

• O-ring is damaged.

• Replace the faulty part(s).

TROUBLESHOOTING

TRAVEL MOTOR

5M0AQ00

TRAVEL MOTOR

“4. Disassembly and assembly, Travel motor”

Hydraulic motor

2nd-speed control

Symptoms

Major causes

Remedies

Motor fails to start

• All the devices other than the motor and

the reduction gears are not working
correctly.

• Check whether the specified pressure is

generated in the inlet port, and then check
and repair each device.

• Pressure oil is not flowing properly due

to abnormal wear of the motor’s sliding
part.

• Replace the abnormally worn out part(s).

• Motor is faulty, as its main components

are damaged.

• Replace the damaged part(s).

Rated speed cannot be
obtained

• Specified volume of flow is not supplied

to the motor due to the faulty oil pump.

• Check whether the specified pressure is

generated in the inlet port, and then check
and repair each device.

• Motor volume efficiency becomes low. • Check if there is abnormal wear on the slid-

ing part; if so, repair or replace it.

Rotational fluctuations are
large

• High-pressure oil is leaking from the

drain port, because the motor’s sliding
part is worn out.

• Replace the abnormally worn part, if any.

• Bearing is worn out.

• Replace the abnormally worn part, if any.

Oil leak

• Oil leak due to O-ring breakage.

• Replace the oil seal and O-ring.

• Oil seal is broken by the internal pres-

sure generated in the motor case due
to the abnormal wear of the sliding part
of the motor.

• Repair the motor and replace the oil seal.

• Pressure increase in the drain piping

caused by the clogging of foreign mat-
ter resulted in breakage of oil seal.

• Clean the clogging in the drain piping and

replace the oil seal.

Symptoms

Major causes

Remedies

Straight-ahead traveling
level is low, switching to
2nd-speed travel is dis-
abled

Spool cannot be switched.

• Foreign matter is caught.

• Remove foreign matter and correct or re-

place the faulty part(s).

• Spring is missing.

• Install the spring.

• Spring is damaged.

• Replace the spring.

• Oil leak due to the abnormal wear of the

2nd-speed control piston.

• Replace the 2nd-speed control piston.

• 2nd-speed control piston is missing.

• Install the 2nd-speed control piston.

• Ball is abnormally worn out.

• Replace the ball.

TROUBLESHOOTING

TRAVEL MOTOR

5M0AQ00

Parking brake

Symptoms

Major causes

Remedies

Braking force is insuffi-
cient or not evenly applied

• Disc surface is faulty.

• Repair or replace

• Spring is damaged.

• Replace the spring.

• Bolt for manual releasing is being fitted. • Remove the bolt for manual release, and fit

the plug.

Abnormal heat generation
due to brake drag

• Release of braking is faulty.

• Oil leak due to O-ring breakage.

• Replace the O-ring.

• Orifice is clogged.

• Clean the orifice.

• Pilot pressure for the releasing is not

working.

• Check whether the specified pressure is

generated in the pilot port, and then check
and repair each device.

Content .. 15 16 17 18 ..