6-2

(1) (1) If even a minor fault is left intact and operation is continued, a fatal failure may be caused, entailing a large sum of expenses and long hours of restoration. Therefore when even a small trouble occurs, do not rely on your intuition and experience, but look for the cause based on the troubleshooting principle and perform maintenance and adjustment to prevent major failure failure from occurring. Keep in mind that a fault results from a combination of different causes. (2) The following following lists up commonly occurring faults faults and possible causes with this machine. machine. For the troubleshooting of the engine, refer to the coming troubleshooting and repair. (3) (3) When carrying out troubleshooting, do not hurry hurr y to disassemble the components. It will become impossible to find the cause of the problem. (4) (4) Ask user or operator the following. ① Was there any strange thing about machine before failure occurred? ② Under what conditions did the failure occur? ③ Have any repairs been carried out before the failure?

troubleshooting. (5) (5) Check before troubleshooting. ① Check oil and fuel level. ② Check for any external leakage of oil from components. ③ Check for loose or damage of wiring and connections.

6-4

Cause YES YES

Remove dust plug under engine flywheel and check if rubber pieces or particles are not present.

Coupling element Disassemble is broken. and repair.

YES

Coupling hub spline is worn or NO hub fastening setscrew is slack.

Remedy

Replace hub or retighten setscrew.

If hydraulic pump or engine is suspected as a culprit refer to this NO manual "Structure and function".

6-5

Cause NO

Is oil level in hydraulic oil tank within standard level?

Remedy Replenish specified oil to

Abnormal noise

YES comes out of

the standard level. Hydraulic pump is Disassemble broken. and repair.

YES

hydraulic pump Do not hydraulic pump and pump YES Abnormal noise YES connections comes out of YES make abnormal pump connection noise?

See item 1). at page 6-5

Is primary pilot pressure within NO standard level?

ⓐ

YES

Clean pilot piping interior or repair piping.

Is not pilot piping YES clogged or is not

oil leakage present on pilot piping? NO ⓐ

Pilot valve is faulty.

Disassemble and repair.

YES

Pilot relief valve is Repair or faulty. replace.

Is gear pump NO delivering oil? NO

6-6

Gear pump is broken.

Disassemble and repair.

3

Cause YES

Water is mixed.

Drop hydraulic oil sample on hot plate and check if foams come up.

Remedy Put hydraulic oil still, separate water and dispose it or replace hydraulic oil.

Air is intruded.

NO

Cause NO

Remedy Replenish

Is hydraulic oil volume proper?

specified oil to the standard level. Clean oil cooler. Secure air circulation route.

YES

Is not oil cooler clogged and is YES anything blocking air circulation?

Check suction line and return line and eliminate the air intruding source.

YES

ⓐ

Is fan belt NO tension proper? Adjust belt tension or replace belt.

NO

ⓐ

Is not the set YES pressure of main relief, relief and travel relief valve Is main relief lower than the valve used very standard level? NO often?

6-7

Readjust set pressure. YES

Reduce load.

Cause NO

Is hydraulic oil volume proper?

Replenish specified oil to the standard level. YES

Replace oil with one of proper viscosity.

Is not viscosity of hydraulic oil YES too high?

YES

Is not suction NO strainer clogged?

Clean suction strainer.

Is not air intruding from pump NO suction line?

Check for air intrusion in suction line and retighten or replace parts.

Cause YES

Has not hydraulic oil passed specified replacement hours?

Remedy

Remedy Replace hydraulic oil to be specified.

Has return filter NO been replaced at NO proper intervals?

Flush with hydraulic oil and replace return filter.

6-8

Cause NO YES Is safety solenoid

YES

Is oil in hydraulic YES tank within standard level?

valve pressure within standard?

Is gear pump pilot pressure within standard level?

YES

NO

ⓐ

Are attachment and travel motions impossible at all?

YES

NO

YES

Is MCV pilot

YES pressure within

Safety valve faulty or not operated. Gear pump faulty.

NO

Are broken pieces of coupling present when dust plug under engine fly wheel is removed?

ⓐ

Remedy Replenish specified oil to the standard level. Repair or replace.

Repair or replace.

Pump connection Disassemble and coupling is broken. repair.

Is not main relief valve faulty?

NO

Hydraulic pump is out of order.

Does swing control valve spool move lightly by hand?

NO

Swing control valve Disassemble and spool is stuck. repair.

YES

Disassemble and repair.

ⓑ

standard level? Does LH travel NO function?

ⓒ

NO

Does not symptom change when front YES NO and rear pump discharge hoses are exchanged? YES

ⓑ

Is swing brake release valve faulty?

YES

Does swing NO motor rotate? NO

YES

NO Is gear pump

Hydraulic pump is

Disassemble and

broken.

repair.

Swing brake release valve is broken.

Disassemble and repair.

Swing reduction unit is broken.

Disassemble and repair.

Swing motor is broken.

Disassemble and repair.

Pilot relief valve is faulty.

Disassemble and repair or replace.

Gear pump is out of order.

Disassemble and repair.

Pilot valve is broken.

Clean pilot piping interior or repair piping. Disassemble and repair.

delivering oil?

ⓒ

NO

Is gear pump pilot pressure within standard level?

YES

Is not there oil leakage from YES pilot piping or is not it clogged? NO

6-9

Cause YES

Swing port relief valve is faulty.

Does swing control YES valve spool move smoothly by hand?

YES Clogged or oil

Clean pilot piping interior or repair piping.

leak.

Is not pilot piping clogged or is not NO it leaking oil?

Single direction Is the trouble in one direction or in both direction?

Pilot valve or shuttle Disassemble and repair. valve is faulty.

NO

Both directions YES

Is Arm speed within standard value?

Does swing YES control valve spool move lightly by hand?

Is MCV pilot pressure within standard level?

YES

NO

NO

ⓑ

Is swing motor's drain rate within standard value?

NO

Swing control valve Disassemble spool is stuck. and repair.

Swing motor is broken.

Check that pilot piping is not YES clogged or oil is NO Pilot valve or not leaking from shuttle valve is it? faulty.

Is gear pump pilot pressure within standard level?

Is gear pump NO delivering oil? NO NO

Is main relief valve setting pressure normal? Is safety valve pilot pressure YES within standard level?

6-10

Does the symptom change when front YES and rear pump discharge hoses are exchanged?

YES

NO

YES

Is gear pump output pressure NO within standard level?

Disassemble and repair. Disassemble and repair. Clean pilot piping interior or repair piping.

Clogged or oil leak.

YES

ⓒ

ⓐ

ⓑ ⓒ

NO

ⓐ

Disassemble and repair or replace.

Swing control valve Disassemble spool is stuck. and repair.

NO

Is MCV pilot pressure same on LH and RH sides?

Remedy

NO

Pilot relief valve is defective.

Disassemble and repair or replace.

Gear pump is broken.

Disassemble and repair.

Main relief valve faulty.

Main relief valve pressure resetting or repair.

Hydraulic pump is broken.

Disassemble and repair.

Shuttle valve is faulty.

Repair or replace.

Pilot relief valve is faulty.

Repair or replace.

Gear pump is faulty.

Repair or replace.

Cause YES Does symptom change when LH YES and RH port relief valves are exchanged? NO Does swing control YES valve spool move smoothly by hand?

Is MCV pilot pressure same for LH and RH?

Swing port relief valve is faulty.

Disassemble and repair.

Shuttle valve is faulty.

Disassemble and repair.

Swing control valve Disassemble and spool is stuck. repair.

NO YES

Check if pilot piping is not clogged or does NO not have oil leakage.

Pilot valve is faulty. Disassemble and repair.

Clogged or oil leak.

Clean pilot piping interior or repair piping.

Cause YES Pilot relief valve is YES

Is MCV pilot pressure within standard value?

YES

Is gear pump pilot pressure within standard level? NO

YES Does swing control

valve spool move smoothly by hand? NO

Is swing control valve's return spring normal?

Remedy

faulty.

Disassemble and repair or replace.

Gear pump is broken.

Disassemble and repair.

Pilot valve is faulty. Disassemble and repair. Swing control valve spool is stuck. Return spring is faulty.

NO

NO

6-11

Remedy

Disassemble and repair. Disassemble and replace.

Cause YES YES Is swing shuttle

ⓐ

valve normal? NO YES Is brake spring

Remedy

Shuttle valve is faulty.

Disassemble and replace.

Brake spring is

Disassemble and replace.

normal? Is return spring of swing control valve normal?

NO

faulty. Return spring of swing control valve is faulty.

NO

YES

ⓐ

Is swing relief pressure within standard level?

Is drain rate of YES swing motor within standard value?

NO

Disassemble and replace.

Swing relief valve Disassemble and repair or is faulty. replace. Disassemble Swing motor is and repair. broken. Adjust swing relief valve pressure or replace swing relief valve.

NO

6-12

5

Cause YES

Is travel brake YES valve pressure within standard level? Has travel YES control valve spool changed over positively?

Does counterbalYES ance spool in travel brake valve move lightly by hand? NO

Does the symptom change when relief valves in NO travel motor are exchanged? YES

Does spool move NO lightly by hand? NO

Is bucket or arm operation possible?

YES

ⓐ

Do not metallic particles come out of drain port in travel reduction unit? NO

Does the symptom NO change when front YES and rear pump Does the discharge hoses symptom change are exchanged? when LH/RH NO travel relief valves are exchanged? YES

YES

Remedy

ⓐ

Counter spool in Disassemble travel brake valve and repair or replace. is stuck. Relief valve built in travel motor is faulty.

Disassemble and repair.

Control system is Disassemble inspect and defective. repair. Travel control valve spool is stuck.

Disassemble

Travel reduction unit is faulty.

Disassemble and repair.

Travel motor is out of order.

Disassemble

and repair.

and repair.

Hydraulic pump is Disassemble and repair. broken.

Travel relief valves are faulty.

Disassemble and repair or replace.

6-13

S

Cause YES

Do LH and RH travel speeds YES change when LH and RH travel brake valves are exchanged? YES

Has control valve spool changed over positively?

Does the symptom change when relief valves in NO LH and RH travel motors are exchanged?

Brake valve is defective. YES

NO

YES

Does the symptom change when YES front and rear pump discharge hoses are Is external pilot exchanged? pressure within NO standard level?

Does travel speed change when YES parking brake spring in the slower travel motor is removed?

NO

6-14

Disassemble and repair.

Travel relief valve Disassemble is faulty. and repair or replace. YES

NO

Is leak rate of travel motor within standard level?

ⓐ

Control valve spool is stuck.

YES

ⓐ

replace. Disassemble and repair.

repair.

NO

Do LH and RH travel speeds change over when NO travel relief valves are exchanged?

Disassemble and repair or

Control system is Disassemble, faulty . inspect and

Does spool move lightly when it is NO cut off from control spool?

Is the lower speed(Bucket or arm) within standard level?

Relief valve built in travel motor is faulty.

Remedy

YES

Hydraulic pump is Disassemble broken. and repair.

External pilot piping is clogged or oil is leaking from it.

Disassemble and clean.

Travel motor's parking brake is not released properly.

Disassemble and clean pilot piping.

Travel motor is faulty.

Disassemble and repair.

None YES Check if parking

brake pilot line is not clogged.

Is travel brake pressure within standard level?

YES

Is drain rate of travel motor within standard value?

Is parking brake friction plate worn?

Cause YES

Friction plate is faulty.

NO

Travel motor is defective.

Disassemble and repair.

Brake valve is

Disassemble and repair or replace.

faulty.

Cause

YES

Disassemble and repair. Disassemble and clean pilot piping.

Clogged

NO

Remedy

Remedy

Inspectaccording to the procedure "Travel does not function at all on one side." However, a case where both LH and RH travel motions are disabled is extremelyseldom OK statistically. Hydraulic pump is Disassemble and faulty. repair.

Is bucket or arm operation possible?

OK

Check oil volume in hydraulic oil NO tank.

Disassemble OK both travel relief valves and Remove dust plug inspect for any under engine fault. Travel relief valve flywheel and Faulty check that there is is faulty. no coupling element particles. Particles present. Coupling at pump connection is broken. Short

6-15

Disassemble and repair or replace. Disassemble and repair.

Replenish hydraulic oil.

(Travel only) Cause YES YES YES Is travel brake

Is travel relief valve pressure within standard level?

ⓐ

Is travel motor's drain rate within standard level? Travel motor is faulty.

NO

pressure within standard level?

Travel relief valve Disassemble and repair or is faulty. replace.

NO

YES

ⓐ

Disassemble and repair.

Disassemble Travel brake valve is defective. and repair or replace.

NO

Remove parking brake spring in travel motor, draw out piston completely, refit cover and check if travel power changes.

Remedy

Increases

Does parking brake piston move lightly by hand? NO

Hydraulic circuit that releases travel parking brake is clogged with dirt. Parking brake piston in travel motor is stuck.

Remains unchanged

Travel reduction unit is defective.

Cause

Travel brake valve (counterbalance valve) is faulty.

Disassemble and clean.

Disassemble and repair.

Disassemble and repair.

Remedy Disassemble and repair or replace.

6-16

Cause YES

Remedy Normal.

YES Is select valve

normal? Is pilot pressure for travel select valve within standard level?

Select valve is

NO

faulty.

YES

Is filter in pilot piping between gear pump and NO control valve not clogged?

Repair or replace. Remove dirt on pilot line filter.

YES Is pilot relief

valve normal? Is gear pump NO delivering oil? NO

6-17

NO

Pilot relief valve is Disassemble defective. and repair or replace. Gear pump is broken.

Disassemble and repair.

6

YES

YES

Is MCV pilot pressure within standard level?

Are other YES attachments operatable?

Cause

Remedy

Port relief valve is Disassemble Does the faulty. and repair or YES symptom change when port relief replace. valve is replaced with other valve? NO ⓐ Inspect if pilot piping is not OK clogged or oil is Pilot valve is NO not leaking from faulty. the piping.

Disassemble and repair.

YES

Pilot relief valve is Disassemble faulty. and repair or replace. Gear pump is Disassemble NO broken. and repair.

Is gear pump pilot YES Is gear pump pressure within delivering oil? NO standard level? Are LH/RH operations possible?

OK

Disassemble

YES main relief valve

Inspect oil NO volume in hydraulic oil tank.

Remove dust plug under engine OK flywheel and check if coupling element particles are not present.

and check if it is not irregular. Faulty

Particles present

YES

ⓐ

Main relief valve is defective.

Cylinder interior is Disassemble broken. and repair.

NO Control valve

spool is stuck.

6-18

Disassemble and repair or replace.

Coupling at pump Disassemble connection is and repair. broken. Replenish hydraulic oil.

Short

Does control valve spool move lightly by hand?

Hydraulic pump is Disassemble broken. and repair.

Disassemble and repair.

B Cause YES

Remedy Normal.

Are other

YES

ⓐ

YES attachment

Is combination YES of oil streams normal at boom hoisting and at arm extrusion?

Is speed low only in composite operation? Are LH/RH travel NO speeds within standard levels?

speeds within standard levels? NO ⓑ YES

Does spool of flow summation check NO valve move lightly by hand?

Flow summation check valve spool is stuck.

Disassemble and repair.

Hydraulic pump is faulty.

Disassemble and repair.

NO YES

Are both LH/RH travel speeds NO low?

Is MCV pilot pressure within NO standard?

YES

NO

ⓒ ⓓ

OK

Does the Port relief valve is symptom change faulty. YES when port relief valve is replaced Does control Cylinder is faulty. with other valve? YES valve spool move NO lightly by hand?

ⓐ

Is not MCV pilot pressure piping NO clogged or is not there oil leakage?

YES

NO YES ⓑ

Is primary pilot pressure within standard level?

NO Is gear pump

ⓒ

NO

Is not orifice in control valve clogged?

Pilot valve is

Clean pilot piping interior or repair piping. Disassemble and

defective. Pilot relief valve is faulty.

repair. Disassemble and repair or replace.

Gear pump is broken.

Disassemble and repair. Adjust engine revolution.

YES

ⓓ

repair.

delivering oil? NO

Is engine revolution within standard level?

Disassemble and

Control valve spool Disassemble and is stuck. repair.

NO

Is MCV pilot pressure within standard level?

Disassemble and repair or replace.

Clean orifice in control valve. YES

Is pilot piping not clogged or is oil NO not leaking from the piping?

6-19

Is pilot valve NO normal?

NO

Clean pilot piping interior or repair piping. Pilot valve is faulty. Disassemble and repair.

Cause YES

Does the symptom change when port Normal relief valve is replaced with Is control valve normal valve? return spring YES Is not hydraulic NO normal? oil temperature high?

Is genuine hydraulic oil or equivalent being used?

Port relief valve is Disassemble faulty. and repair or replace. YES

NO

ⓐ

Control valve's return spring is faulty.

Disassemble and replace. Locate the

Abnormally high.

cause of hydraulic oil temperature rise and lower it to proper level. Replace with genuine hydraulic oil or equivalent.

NO

OK

Disassemble and YES inspect check valve in hydraulic circuit and check for any fault. ⓐ

Remedy

Is cylinder internal leakage within standard level?

Abnormal

Pressure tightness between control valve casing and spool is poor. Contact surface between poppet

Disassemble and repair.

Disassemble and repair.

and seat is poor. Cylinder is faulty.

NO

6-20

Disassemble and repair.

Cause YES

Check according to the procedure in Item "Speed is low".

Is cylinder YES internal leakage

Is relief pressure in main relief valve within standard level?

within standard level?

Is relief pressure YES in port relief valve within standard level?

Cylinder is faulty.

NO

NO

Main relief valve

Adjust pressure,

is defective.

repair or replace.

Cause YES

Does the YES symptom change when port relief valve is replaced with other valve?

Is RH travel possible?

Is MCV pilot pressure within standard level?

Does control valve spool NO move smoothly by hand?

NO

YES

Does the symptom change YES when hydraulic pump's discharge hoses are exchanged?

6-21

Remedy

Port relief valve is Disassemble defective. and repair or replace. YES Cylinder interior is Disassemble broken. and repair.

NO

Does the symptom change when NO main relief valves are exchanged? NO

Disassemble and repair.

Port relief valve is Adjust pressure, faulty. repair or replace.

NO

YES

Remedy

Control valve spool is stuck.

Disassemble and repair.

Pilot valve is faulty.

Disassemble and repair.

Main relief valve is faulty.

Adjust pressure, repair or

replace. Hydraulic pump is Disassemble broken. and repair.

Cause YES

Remedy Frictional noise occurs between the sliding faces of boom cylinder's oil seal and boom proper. ※ Frictional noise will disappear if they are kept used.

Is boom foot pin greased sufficiently?

Boom foot pin has run out of grease.

NO

Supply grease . ※If seizure is

in an initial stage, supply sufficient grease. If seizure is in a grown state, correct it by paper lapping or with an oil stone.

6-22

※

1. Lower the bucket teeth to the ground with bucket cylinder fully retracted and arm cylinder rod retracted almost in full.

29076TS01

2. Disconnect hoses(A) from rod side of boom cylinder and drain oil from cylinders and hose.(Put cups on piping and hose ends)

A

6-20(2) 210-7

3. Raise bucket OFF the ground by retracting the arm cylinder rod. If oil leaks from piping side and boom cylinder rod is retracted there is an internal leak in the cylinder. If no oil leaks from piping side and boom cylinder rod is retracted, there is an internal leak in the control valve. 29076TS01

6-23