L783 Boom/Bucket locking up

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Jun 20, 2022
L783 Skid Steer boom and bucket issues

I have a New Holland L783 skid steer, it’s almost exactly the same as the L785 skid steer. Im having an issue with the hydraulics. Moving the machine in forward and reverse and turning is zero issue. The machine does it fine. The issue comes when using the foot pedals to operate the boom and/or bucket. When operating either at full throttle, they will “lock up” within 30 seconds of use, if not in less time than that. It’s more so the boom that locks up first, then takes the bucket out with it sort of thing. When the boom locks up, most of the time the bucket is affected in some way and locks up as well but sometimes the bucket takes a second itself to lockup with the boom for some reason. The way I free these, is I’ll lower the throttle to idle, and within a few seconds of waiting, I’m able to boom down with the foot controls no problem. I found that if I operate the boom and bucket at idle, they do not lockup at all like they do at full throttle. I also found that if I operate the boom/bucket at full throttle but only slightly depress the pedals to move the boom/bucket at a very low speed, they will not lockup. So it seems the issue comes into play when the hydraulics are moving at their maximum speed/flow. Once this lockup happens, if I remain at full throttle and try to boom up or down or bucket tilt, it will sound like the pressure relief in the control valve for the boom/bucket is kicking in (sound it makes when tilting the bucket back all the way and holding it). I can see the bucket/boom make an attempt to move when it is “locked up” when I rock the pedals back and forth but again, you just hear the pressure relief kick in. The pins seem to be in good shape, the cylinders don’t leak, I haven’t noticed cylinder drop and I just used this to move 40y of rock weeks ago.

This issue seems to have progressively got worse as before it did it once in a rare while. Now it happens basically anytime operating boom/bucket at full throttle. Again to restate, at idle when operating the boom/bucket, it doesn’t have this lockup issue at all. Any help, similar experiences or ideas anyone has to share is greatly appreciated. Linked is a free service manual I found on almost the same exact machine (L785 but I believe they are identical), on page 1-3 is a schematic for the hydraulic system.

P.S. The seat activated boom lockout is disabled on this machine and I verified that. I also know these machines have bypasses if the filters are plugged. I did clean the hydraulic screen filter/magnet. When it locks up, I still have full range of motion on the pedals. No load is in the bucket and sometimes the bucket isn’t even on when troubleshooting this. Thank you!