951C 86J3065 I'm sure this question has to have been answered a 100 different ways, but have not found quite what I am looking for. Apologies in advance. I just got the unit back from the cat dealer. They rebuilt both tilt and tilt cylinders, the bores did have some scouring, but thought it not too bad. Issue is the bucket tilt does not hold at all. The lift circuit holds just fine so suspecting this is a control side problem rather than a cylinder issue. I was looking at the kick out and relief valves in the service manual. I know I need to set up test rigs and go through those calibrations, but as it tilts and goes to the stops with what seems significant force. But as soon as it is in the hold position, the bucket immediately starts to drop. I've not timed the full droop time yet, but it goes from all the way tilted up to flat in around a minute. Will get a more accurate number later today. Is there another path I should be looking at. As everything I've seen in the book and here on the forum seems to focus on the cylinders, maybe the scoring Is just worse than I think and the call to rebuild was wrong? I've looked through the test info available in the book I have, and se how where the block plates and such go, but seems to be mussing something in diagnostics. I'm guessing that if the pressures from the text are in spec, and the relief valves are set right, I out the cylinders. And these should... Have been shop tested. Could the bucket position circuit be a problem? Or am I likely to need to drain the system, pull the tank open, and go through the pilot block? Just did not see any good trouble shooting for that side of the system. All help, suggestions, rants, and doubts on my sanity, comprehension (and forum search skills) welcome! Thank you.
It falls a bit slower than I thought take a couple mins to go from full reurn to about flat. Does not hold at all when it is tilted all the way back. It does hold in the other direction. Inset the bucket flat on the ground and tilted it down, dump, until I got the front end off the ground enough to know it had weight. Held just fine. So it does not hold to keep the cyliders from extending, but does keep them from compressing. Making an assumption that unless both cylinders had pretty bad internal leaks, in same direction, that the culprit has to be something common in the circuit? Could of course be totally off base, as my depth of understanding of how this thing works is pretty rudimentary.
Sounds like a line relief is leaking past to me. Would have to consult the service manual for location. Could confirm by swapping the rod end and head end line relief and see if the problem goes to the other side of the cylinder.
I had same issue after piston broke in 1 of the tilt cylinders. After i rebuilt both tilt cylinders the bucket would not hold when bucket was used to say back drag. Split hydraulic and pulled relief vale. Had a piece piston metal lodged in there. Removed metal and issue gone. Have pic and will post
Pic
Thank you! that is very helpful!