I have a 2012 CAT 252B3 s/n TNK01281 with 2,800 hours on it that started to occasionally drop implements. It looks like the quick attach pins are actually retracting even though the handles are locked in position and the lock is over center where is shouldn't allow retracting of the pins -- at least that's what my mind tells me. The pins seem to extend far enough through the implement. But when backdragging, the implement rides on the pin taper which allows the pin to push back up and release. Here is a shot of the pin fully extended. Is there a wear item in there that could be allowing this? Or something I can adjust? It hadn't been an issue in the past and just started happening this summer. TIA
Most times the problem is wear on the quick attach. Check for a gap between the skid steer and the bucket at the pins with the bucket in the air. If it does need shimming check it with your other attachments to see if its the skid steer or the bucket. If it needs a shim you buy steel and weld it in or build up your skid steer side. What can also happen is on some models the latches have springs and they get tired and leave the pin retract.
It's definitely something with the quick attach plate on the loader 'cause it happens with all my attachments. There's not really any gap at the bottom of the plate (between QA plate and attachment). I've actually had to bend my grapple back so there is zero clearance with the QA plate and it will still get bent again and separate. I added gussets to the grapple so it won't bend and now I can just watch the pins retracting when putting back force on it. Mine does have springs. Maybe they are just worn out. I was thinking there should be a mechanical lock when the lever is down and over center that blocks the pin from coming up. But that's obviously not the case since the pins are able to move. Not sure why they would want a spring holding it when it's supposed to be locked. I was thinking the spring just kept the handle from moving without someone intentionally moving it. You can see the spring in this image (below and to the right of the nut). There really isn't much room to inspect anything in there. I'm guessing removing the nut allows the whole assembly to come out.
If it does it on all your attachments it would seem to be the skid steer. I am unfamiliar with Cat but sometimes there is roll pins or such to keep the springs in place, if those are sheared it doesn't put enough force on the pin. My next guess would be springs if it isn't in need of shims.
On my Bobcat T300 I had the same issue. To fix it I welded two 1/4" pieces of plate on the top portion of the quick attach on the machine to take up the slack. Works great now. Actually a little tight for a couple of my attachments but it is wearing in.