JCB 214, left outrigger cylinder will drift down when machine is stopped. New seals installed in cylinder, no obvious scarring of barrel or piston, and new hold valve. Drifts at a rate of 1 inch every 15-20 minutes and will be on the ground overnight. Noticed cylinder will also drift under a load holding the backhoe up at about the same rate. Removed hose connections at control valve side of hold valve while the outrigger was up in stowed position eliminating a control valve connection to the circuit, same drift at the same rate. Switched hold valves with the other side that works fine to eliminate the possibility of the new hold valve leaking internally, same drift at the same rate. Pretty much tells me there is still some type of leakage in the cylinder between the barrel and rod end of the piston.....somehow. What say you geniuses here? :Banghead
Is there a seal where the piston is bolted to the rod? I don't know if all cylinders use an O-ring on the middle of the piston but on my skid steer I noticed the piston was 2 pieces and had to go together a specific way so as not to damage the inner O-ring.
Yeah, drifting with the rod extending sounds like a leak, either a scratch in the bore, or if you have already resealed the piston, perhaps a leak between the shaft and piston.
I am not a genius but I will make a comment. As already suggested it may be a rod to piston leak. But, there is a chance the seals were damaged when the piston was inserted in the barrel. It is quite easy to scuff the seals by letting them contact the barrel threads. Or the seals were assembled wrong.
There is a seal on the rod that seals the piston threads when the piston is screwed on, and it is a single piece piston.
I can't imagine the new seals being damage during installation. When I removed the rod originally I couldn't see any damage in the barrel or to the old seals on the piston. The seals are easily identified so them being placed backwards or the wrong order is almost impossible in this application. I will be disassembling the cylinder again next week to do a closer inspection of the internal surfaces. Keep the suggestions coming because I'm at a loss at the moment.:bash
I believe we may be on the same page here my friend.:cool2
Just because you can't imagine it - doesn't mean it didn't happen. What was the cylinder doing that caused you to rebuild it? Is it better now or the same?
Well we just repacked the arm and boom cylinders on a fairly new Case 160 excavator and the arm cylinder twice come to find out the second time after checking them and the tube with a micrometer the rod packing directly from Case was undersized. Also have seen the barrels swell and then the seals will not hold.
On my cylinder I remember there was a taper to allow the piston to fit easily over the inner o-ring. It could bugger the o-ring if installed backwards.
The exact same thing, only its a bit better at the moment.
I just repacked both of my tilt cylinders, and noticed I'm drifting much faster than I would like. I also noticed my lift cylinders were raising slowly without my touching the control. The machine has been down while I rebuilt the transmission for several months until today not really sure what's going on but hoping the machine is just needing to be run a little bit. was your issue resolved?
Check your control valve is centering. Dirt in the linkage or sticking linkage maybe or dirt in the valve. It the cylinders are raising on their own it's not from the cylinder seals.
If it is drifting up (hoe lifted and engine off) I would think it would have to be in the cylinder because you have swamped hold valves. You could swap cylinders just for exercise but my bet would be internal leak between piston and rod.
i would extend the cylinder alll the way out and with the machine on jacks and cap of the barrel end of the cylinder and leave the rod end open, then lower the jacks to determine if its bypassing the piston
Man, sometimes I forget to go back on these threads and give a final result. Yes, I found the problem. Someone had been into the cylinder before me and had cut the piston off the rod with some type of reciprocal or rotary blade. In doing so they got it too deep and had cut a small itsy-bitsy line into the inner piston seal surface on the rod. I missed it the first time, but realized when I took it apart the second time that oil was leaking past the piston right there. I welded the gap, ground it down and that worked perfectly.
Who the heck would do that???
If it is like mine, they probably did not see the dowel pin hidden under a seal. It won’t unscrew with that still in place.