luvbug -
I checked my
B7610 Kubota Workshop Manual - the FEL and BH are not included (must be separate WSMs) - but I did look over the hydraulics & troubleshooting tables. Your symptoms had me perplexed before I even opened the manual!
Some things to think about:
1) The FEL hydraulic attachment point is in series with (in-line / before) the 3PH lift control - so if the hydraulic pump were the problem - then the 3PH shouldn't work either. However - since you could RAISE the FEL - that clearly indicates you have pressure....
The hydraulic pump is an internal gear type - it runs continuously in proportion to the engine speed. The hydraulic pump is actually a "double-pump" - a 2nd gear pump (lower flow capacity) running off the same drive shaft supplies the power steering exclusively. If the hydraulic pump shaft had failed - then you would have had no power steering either.(think VERY expensive shear pin!)
My experience (13+ yrs industrial hydraulics) with gear pumps is that they are extremely durable and can take quite a beating. (The HST "variable pump / motor" is more complex and needs a bit of care - just keep up with the scheduled fluid changes)
2) The WSM asks if there is "noise" or "no noise" when attempting to move the implement? "No noise" clearly means no hydraulic oil is going anywhere - I'd think the "whine" ("noise") of the hydraulics would have changed if the cylinders were working - but "struggling against" a blockage.
3) Was the raise speed of the FEL / BH *normal* - or was it "slower than normal"? (As your complaint is "lock up" - I assume it isn't faster in any case! /forums/images/graemlins/wink.gif )
Slow in one direction / no movement in the other suggests that the spool of the control valve could be jammed / mechanically limited - but this falls apart IMO - because you have two different implements / control valves acting the same way?!?!
4) If the hydraulic pressure relief valve were stuck open - you should not have had pressure to raise the FEL / BH!
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So where does that leave us? Assuming the pump is OK (pressure to lift FEL / BH), and it is unlikely that two separate control valves jammed in the same way / at the same time - my guess would be some kind of stuck check valve in the return / tank line of the cylinders - especially if the hydraulics are shared between FEL & BH.
I'm not entirely thrilled with this explanation either - as the FEL for example - uses the "small side" of the hydraulic cylinders for lifting the bucket - so the lowering side has the bigger piston / surface area ( = more force --> that's why you can lift the front tires easily when you apply "downforce") - which
should mean that it would be easier to force open a stuck check valve when LOWERING the FEL - if that were the problem....
Sometimes check valves are "pilot controlled" - meaning that some other device *decides* whether the check valve is allowed to open - not just the flow / pressure of the oil passing through the check valve itself.
If the "pilot controlled check valve" theory is correct - this would explain why the FEL / BH could be lowered with the engine off: the "pilot pressure" to hold the check valve CLOSED is missing.
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Glad to hear that everything is working again - I'd sure like to know what the dealer says - an interesting problem to say the least! /forums/images/graemlins/confused.gif
Hope that my ramblings help,
Dan
