Kobelco SK 100 mark 4 ser. # YWU1110 My old girl has become mixed up. This condition has slowly become worse. When I try to swing left or right, stick starts to move in by itself. If I stop trying to swing, stick continues to come in for a few feet before it stops. If it try to do stick out it is a very violent short motion and then it stops. I have had experts telling me to check out various check valves and spools with no improvement. Any help finding root of this problem would be greatly appreciated.
Do you run ISO (excavator) style controls? If so sounds like your pilot control valve is worn out. This is the valve under your control lever.
Both pilot control valves are NEW and their replacement had no affect on this condition
Going to need an old master to figure out the problem with this machine as she is about 28 years old and is all hydraulic control no electronics.
Not an old master, but I'm curious... it looks to me from the parts pages that the swing valve is actually on the swing motor? Wish I had a service manual or at least a schematic. Have you pulled the arm spool for inspection and the associated port relief valves and poppets? I'm guessing here, but if I'm following the layout correctly the only interaction between swing and arm function would be some sort of backpressure to the main valve block when the swing valve is shifted. Unless of course there's an issue with the pilot lines or controllers. Have you verified pilot pressures at both ends of the arm spool when moving the arm function and also when swinging?
Yes swing valve is on the swing motor. Swing spool and arm spool have been removed and inspected both looked just beautiful, like new. I will be trying to do pressure checks this weekend. Wish I could get a hold of a real factory service manual and I don't mean the one kobelco sells to the end user as a factory service manual, as I found out there is a big difference in them.