mpb Posted April 17, 2022 Share Posted April 17, 2022 I’ve got a Bobcat mini digger that the seals on one of the rams has started to leak. Can anyone offer any advice on resealing a hydraulic cylinder, is there anything to watch out for. Obviously making sure things are clean, are going to be high on the agenda. Many thanks Martin Quote Link to comment Share on other sites More sharing options...
landroversforever Posted April 17, 2022 Share Posted April 17, 2022 Clean being the first one, and then where the seals go, is it actually the seals that are no good or is it the sealing surfaces? No point changing the seals if the chrome is scored for example. 1 Quote Link to comment Share on other sites More sharing options...
Stellaghost Posted April 17, 2022 Share Posted April 17, 2022 12 minutes ago, mpb said: I’ve got a Bobcat mini digger that the seals on one of the rams has started to leak. Can anyone offer any advice on resealing a hydraulic cylinder, is there anything to watch out for. Obviously making sure things are clean, are going to be high on the agenda. Many thanks Martin I would imagine you are buying a new seal kit, obviously lots of care in fitting new kit, check the cylinder bore and the piston / ram for any signs of roughness that could have contributed to the seal failure, check the piston for any signs of pitting. Any rough surfaces will need to be smoothed off with fine grade wet and dry paper, same with the cylinder bore. If the ram is pitted smooth off any roughness degrease and then score pitted area with some 80 grit emery paper, coat the pitted area in araldite and allow to harden then you can sand it down until your ram is smooth again ( used to do this on motorcycle forks )Use plenty of lubrication when putting back together regards Stephen 1 Quote Link to comment Share on other sites More sharing options...
smallfry Posted April 17, 2022 Share Posted April 17, 2022 Normally the rod seal is the first to go, usually because the wiper seal is worn. The piston seals will not cause any external leakage. What I do with mine is leave the cylinder on the machine to loosen the gland as I do not find vices or clamps hold the cylinder body very well, then remove the body pin and slide the cylinder off of the piston. Then you can undo the piston nut with the rod still attached. Save a lot of backache this way, as you will not be lifting the complete cylinder. You will get a fair bit of oil spill, so be prepared for this. Make sure the chrome rod is well padded and not allowed to hit anything, and never, ever, grip the rod with stilsons Make sure you note how it all fits together. Its actually very easy, and they are self bleeding You can buy seals from a specialist for a lot less money once you have the sizes ! All my Yanmar cylinders use the same seals, so I always keep a set in hand. I found all mine started to go in fairly quick succession, so I guess it was an age thing ? I always park the machine up with the piston rods retracted into the body to protect them. 2 Quote Link to comment Share on other sites More sharing options...
mpb Posted April 18, 2022 Author Share Posted April 18, 2022 Thank you all for the advice. The rod doesn’t look pitted, I think it’s an age thing as the machine is about 20 years old. 1 Quote Link to comment Share on other sites More sharing options...
muddy Posted April 18, 2022 Share Posted April 18, 2022 Give any nuts and locking rings a waft with a blowtorch, this softens the thread lock with can often make undoing them nigh on impossible. Also check for the right number of seals as wiper seals can sometimes get spat out and lost making assembley confusing. Cutting Edge Engineering on YouTube has lots of interesting videos on rams. Quote Link to comment Share on other sites More sharing options...
mpb Posted April 18, 2022 Author Share Posted April 18, 2022 Many thanks I’ll take a look Quote Link to comment Share on other sites More sharing options...
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