2005 Kobelco SK70SR-2 Need advice from a Kobelco expert. Lost boom lift and arm extend.

[CrazyD]

I recently had to replace the instrument cluster as the original died and I could not read any info when I ran my machine. In the process the hydraulic fluid may have gotten pretty low and when I started the machine the boom would not lift nor the arm extend. It would come down and in and now I cannot raise them again. I tried checking the main pump for any air but the fluid was clear. I tried loosening pilot lines to bleed any air from them, but at idle not much pressure and only clear oil leaked out. I did let the machine run for 2-3 hrs hoping if the oil got hot it might work out the problem...but it did not help. I do not have any pressure testing equipment for further testing and have not run the diagnostic menu on the machine. I need advice on what steps to take next. I have not yet able to get a mobile mechanic out to look at it yet. Any good suggestions are welcomed.

 

[Simon C]

Boom up and stick out are 2 different joy sticks. Not sure how to get codes out of display if possible without software. Unless if both those functions use a common ground somewhere in the cab, be worth checking, and even if it isn't you can rule that part out for the next round of problems.
Schematics would help a lot if you can borrow or buy and worth it cause machines now a days always have electrical problems of some sort.
Simon C

 

[CrazyD]

Good advice. I think this system uses actual pilot pressure lines to both joysticks but maybe there is an electrical angle I have not thought of. I will look into that. Hopefully I can find a mechanic here familiar with this type of machine.

 

[Simon C]

If you are into pilot line joystick controls, then you probable need to find which spool is boom up versus stick out on the pilot lines and check if some rubber went and plugged the lines at the main control valve.
Could check for pressure at those locations also.
Simon C

 

[alexcbh]

I'd start with the simple stuff before worrying about the pump.

Low oil can cause all sorts of odd hydraulic problems if it pulled air into the system. Just because the oil looks clean doesn't necessarily mean all the air is gone.

The other thing I'd want to know is whether you've still got pilot pressure. If the pilot circuit isn't building pressure, the boom and arm won't respond even if the main pump is fine.

One question...does it still swing and travel normally? If those work, I'd probably spend more time looking at the pilot side or the control valve before condemning the pump.

 

[HarleyHappy]

Have you tried putting a little positive pressure on the tank with a rag and an air line?
Some shop vacs suck and blow, I have successfully bled a Hitachi that got air bound and got low on fluid.
As soon as you stroke more than oil is in the reservoir, you are cavitating the pump and pushing air. If you have done that there could be air all over.
The pilot pump is usually the problem.
Might have to bleed it manually.

 

[Simon C]

Using a vacuum to blow works, always have to remember that the hose could have something in it that is sitting loose and suddenly is in the compartment.
Always better to use compressed air unless the hose is brand new and no dirt has passed through.
Yes manual bleeding of hose after pump works well to get oil moving.
Simon C