I am working on Bobcat S300 (2003) which was leaking oil out from lift cylinders and was creeping down so fast that you can tell it just by looking the arm. So all the seals were pretty worn, replaced them and made sure that cylinders were in working order. But the lift arm is still creeping down, just much slower than before and no oil leaking out. Replaced both BICS-valves since lift side valve seals were little bit worn, no noticeable difference. Any ideas where to look next?
i'd swap the lift and tilt lock valves and see if the problem goes away. it's possible that the retainer bolt for the centering spring/detent assembly on the lift spool may be loose. :drinkup
New lift and tilt lock valves and no loose bolts, arms still coming down. Could faulty bucket positioning valve cause this? Or how likely lift spool would be so damaged that it would let this much oil trough? Also found pieces of broken ~30-50 mm o-ring from the hydraulic filter . Everything else works fine, arms just comes down slowly.
To rule out the cylinders I'd raise the lift arms and support them with another loader or hoist and block off the ports on the cylinder then take away the support. If it goes down then you still have bad cylinders. Steve
it's a possibility the bucket position valve could be leaking internally. probably not that the spool is damaged, but that the spool bore is worn, or the valve is cracked internally :drinkup
I tested the cylinders exactly in that way. I raised the cylinders up, supported arms with forklift, blocked lift ports of the cylinders and lowered forklift so that the lift arms were free. Waited 60 minutes and no movement at all. So I am sure the cylinders are fine and no oil leaking out so the fault must be in some valve. I think the fault must be either in bucket positioning valve or in lift spool/valve block.
Quick and dirty solution, plumb in a vented counterbalance valve on the lift line, something like this would work: http://www.sunhydraulics.com/assembly/CWCALHN-MAK