Hi everyone, I have bought a Yanmar Vio15-2 circa probably 2004, 5,600 hours, with "weak hydraulics". Expected the pump is worn and needs a rebuild (I rebuilt a similar pump for a compaction roller not long ago so was not too scared about that). Upon delivery and inspection I found that it indeed felt weak in boom functions. Started looking at simple things first and found a small stone was stuck inside the high speed pedal, keeping the swith pressed while the pedal lost some of its travel. After removing stone there was a marked improvement in all functions, however it still would not lift one track off the ground, unless I simultaneously curled bucket as well. Spent some time reading this forum and found some people saying that was not unheard of for these small diggers (I have an old Hitachi from early 80s and it lifts its side almost on just above idle). Next I measured pressures - this pump has two outputs. They both maxed out at 2,500psi cold, the manual says 2,984psi. I tried adjusting relief valve on the side that does boom lift etc, I could adjust it to 3,200psi and probably more - set to factory setting. The other relief valve was pain to access but I managed to. This valve though even when screwed all the way in did not change pressure on that pump outlet. How do I interpret this? The pump physically is one pump, so can I rule it out since it clearly is capable of producing pressure - OR could it be that one side of valve plate is worn more and is leaking more on one output only? I still am not sure about this valve, it made no difference at all, so is it a higher probability that it could be stuck or spring broken? (when winding in it does feel like there is a spring but hard to tell more than that). It is VERY hard to get to it without removing whole pedal and lever assembly and disconnecting about 6 hoses from the valve block. Any suggestions or maybe someone has faced such a situation where one side of pump refuses to raise pressure? Many thanks!
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