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kobelco sk120 mark v critical problem

rankothge

Well-Known Member
Joined
Aug 12, 2013
Messages
143
Location
sri lanka
kobelco sk 120 mark v long arm
this machine repaired cobelco agent, these are they have done.

main hydraulics pump overhaul
pilot pump change
pump proportional solenoid change
all filters & hyd oil change
pressure relief valve change

but still machine is not OK.

:Banghead:Banghead:Banghead:Banghead

both tracks is OK. ( relief pressure 350bar )
boom is not OK. ( relief pressure approximately 170bar )
arm is not OK. ( relief pressure approximately 180bar )
bucket is not OK. ( relief pressure approximately 190bar )
swim is not OK. ( relief pressure approximately 180bar )
when backup switch is on no condition change (no pressure go up )
repair persons said valve box has a internal leak
i think all port valve is OK.
dear all my group any idea do you have for this ?
thanks in advance
 

Ben Witter

Senior Member
Joined
Apr 3, 2013
Messages
263
Location
On the outside
The straight travel valve only dedicates pump flow so that one pump supplies the tracks and the other supplies the working hydraulics. Your problem is most likely a leak internal to the MCV. What happens when you operate 2 functions at the same time such as arm in and boom up?
 

rankothge

Well-Known Member
Joined
Aug 12, 2013
Messages
143
Location
sri lanka
thanks for advice Mr ben witter
operate 2 functions at same time machine change little slow
bucket & arm operate individually i show the display p1 or p2 bypass cut proportional vale readings not change. low pressure sensor readings ok
when i tried to do 'A' adjustment display shows 'CPU condition error'
this is a machine serial no lp 13684
i want check CPU serial no and machine serial no is mach. can i know correct cpu serial no on this machine?
 

hatorade

Member
Joined
Apr 21, 2018
Messages
22
Location
Fruita, Co
The straight travel valve only dedicates pump flow so that one pump supplies the tracks and the other supplies the working hydraulics. Your problem is most likely a leak internal to the MCV. What happens when you operate 2 functions at the same time such as arm in and boom up?

Ben Witter I have a 1993 Kobelco SK120 #LP-07713 All functions are working however they are slow. However when you walk the machine and slightly engage lift on boom or swing or anything the machine speeds up not just the tracks but everything. Also just digging if you apply slight pressure to the tracks not enough to engage the digging speeds up again.
I have tested the pilot pressure at port P3 and get 500 psi all the time, I dead headed the boom and got 4500psi from port A1, i put the bucket against the track and got it up to 3000 psi from A2 before i stopped. I have removed both solenoids on the pump and they seem to be in working order, i also increased the Master relief valve by tightening it 2 turns slight change. I have also changed the filters checked the screen but it still almost lurches forward when both tracks and digging are engaged. Any thoughts or places to start would be greatly appreciated!
 
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