I recently bought a good condition JCB214e and replaced the seals on the right rear stabilizer arm after replacing the ram as it was slightly bent. The stabilizer held pressure in both directions and apart from being bent worked 100%. After replacing the ram the arm will extend and raise the machine's rear wheels off the ground and remain like that for a full day with the machine switched off. If I however raise the stabilizer and switch off the machine it will immediately start to slowly drift back to the ground, only under the weight of the stabilizer arm itself, going all the way to the ground in the end. The seals obviously holds pressure when raising the machine, so I am hesitant in saying it is a seal problem. Any pointers, maybe trapped air somewhere and if so, how do I bleed it?
The air will bleed itself out after running thru a few full cycles, no need to do anything special there. More than just the seals have to hold the pressure, the valve could be where it's leaking down. The tube, piston or gland could be out of round or have some gouge or damage in there from when the rod was bent, the new seals could even be causing it if they are a hair undersized or were cheap ones. Costs a bit, but it's always best to have a machine or hydraulic shop check the whole thing out when the rod gets bent, as that's for sure the part that will take the most abuse and everything else related there at that point is suspect to being a little bit off, and that's all it takes sometimes.
Are you sure the piston is tight
Thanks for your replies. Yes, the seal is tight, OEM seals bought from JCB, received in their own sealed and branded packaging. Also thought it would bleed itself. Initially it would not hold pressure in either way, but this morning, after working the stabilizer up and down quite a few times, I eased off the supply lines and a good deal of air escaped from one side. Since then it would hold pressure in the extended position, coincidentally the side the air escaped from. Could not get air released from the other side, but still would not hold pressure. Might have pushed the air up the system towards the valve bank, dunno? Positive the cylinder is not damaged or scored, hence the only thing I could think of was more trapped air. Not sure how it could result in the cylinder losing pressure in order to slowly drop position. Not impossible that the seal was damaged when I put it in, but unlikely. If so, is it possible to hold pressure in one direction, but not the other?
The air might have been working toward your benefit to hold up the stabilizer. Any leakage volume in the extend side is taken up by the compressed air. The retract side holding the stabilizer up may be leaking and under the pressure of the trapped air in the extend side of the piston.
Yes, it is possible to hold in one direction over another. Scenario 1 , the piston to rod seal has failed. This would hold pressure when pressure is applied to the plus or barrel side. In opposition when pressure is applied to rod or negative side, oil may slip between rod and piston. Scenario 2 , you have a load holding valve on the plus side only, that would physically trap oil in the cylinder til a signal is applied to the valve to release the oil. Scenario 3 , you have a scratch or perhaps an oversized bore in the middle or end of the barrel. This would allow oil to escape past piston packing regardless of age. Most likely when cylinder is in full extension. (Not your situation) Scenario 4 , least likely of all, a scratch on the spool or valve body. This , you would feel. It would stick, bind etc. Hope these shed a little light into what direction you want to pursue.
You can pull the lines off and put caps on them to see if the problem is in the cylinder also. That way all the fluid/air that's in there should be trapped in there. Quickest way to see if it's cylinder or valve related.
The bend in your ram when extended will not effect anything with a good seal but when fully with drawn your putting pressure on one side of the seal that's why it won't hold. Get the ram straightened at least within 4 or 5 thou. and you'll be fine.
When installing a cylinder and operating it the first time it is possible to burn the packing rings. I used to only slightly move the stroke a couple of inches each way to start with and gradually increase the amount of stroke until the ram reaches each end of the stroke. All this was done with the engine at low idle. I also left the reservoir cap loose so the air would exhaust out of the system easily.
One thing to note, a failed piston seal will only ever cause a cylinder to drift outwards, never inwards. Bypassing fluid from the base end will not be able to occupy the rod end due to the smaller volume of space in the rod end.