Pc 138-8 hydraulic problem

[Brad789]

I have a 2012 komatsu 138 and it is having hydraulic issues. Machine has 4300 hours on it and have had this issue since 900 hours on it. The boom now and then come to a complete stop and as fast as you let off the lever and try again it would work. The dealer un hooked the relief valve on the bottom of the control valve and it made the boom stopping issue go away but the boom never moves at the same speed. It is a nightmare to grade with because the boom is never consistent It either puts too much pressure down while grading or it will pick up off the ground. Our local dealer and komatsu Canada doesn’t know what’s wrong they turned pressures down which just made the problem slower.The local dealer said it could be control valve but not confident it is the problem.hydraulic temperature has no effect on how the machine works. Any suggestions of what I can try to fix would be appreciated before I buy a 20000 part.

 

[uffex]

Good day Brad
Have met a similar issue with another make however I suggest you check out the spool for free movement be aware of fluid loss, often missed is the spring mechanism see attached.
Kind regards
Uffex

 

[John C.]

Do you know how to get into the monitor panel diagnostics section?

I'm a little concerned about the statement of

The dealer un hooked the relief valve on the bottom of the control valve and it made the boom stopping issue go away but the boom never moves at the same speed.

I don't have any idea of what is going on there nor of what they did. What you are describing seems to only affect the one function of boom up and I can understand your aggravation about fine control and making a smooth and level dig. I think I would get into the monitor and check out the signals from the pressure switches for the boom up and down functions to see if they are working all the time. Mr. Uffex is also correct in checking the mechanical things like springs and spacers and such on the ends of the hydraulic spool for boom up and down control. There are plenty of other things to check but we should start at the easy and least expensive stuff first.

 

[Brad789]

Do you know how to get into the monitor panel diagnostics section?
Spool has been removed and checked 3 times. If the relief valve is hooked up and I swing and raise the boom it comes to a stop. There is also nothing in the diagnostics. It has been to the dealer 5 times and I’ve had another mechanic look at it who also checked out the spool and they can’t find an issue.

I'm a little concerned about the statement of

I don't have any idea of what is going on there nor of what they did. What you are describing seems to only affect the one function of boom up and I can understand your aggravation about fine control and making a smooth and level dig. I think I would get into the monitor and check out the signals from the pressure switches for the boom up and down functions to see if they are working all the time. Mr. Uffex is also correct in checking the mechanical things like springs and spacers and such on the ends of the hydraulic spool for boom up and down control. There are plenty of other things to check but we should start at the easy and least expensive stuff first.

 

[Chris$$$]

Good morning, I'm having a similar problem with my 138-8. But it's mainly the bucket and swing. They both will slow right down to almost a stop but once you open another valve like the boom it will move normally. Have checked pilot pressures. Are normal until it slows down. Any suggestions on what I should check ? Machine only has 3800 hours. This problem just started suddenly. Thank you for any help with this matter.