Hydraulic Cylinder Rebuild

General Discussion

  1. BigblueC

    BigblueC Well-Known Member

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    My tractor has two leaky cylinders that I've pulled off to have rebuilt this coming week, but at local shop rates of $80/hr and expect 2hr per cylinder + parts (I was told ball park $750 by my kubota dealer), I'm wondering if this is something I can pick up the parts for and do myself.

    So do any of you guys have experience here? I'm confident in my mechanical abilities but this would be my first time with a hydro cylinder so I'm not sure of what to expect in terms of difficulty or if there are specialty tools needed. What do you guys think, should i crack 'em open and see what happens or bitch and moan about shop rates?
     
  2. Davea Lux

    Davea Lux Old Man with a Hat FCBO Gold Member

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    That is a pretty typical rate for shop work these days. I might be cheaper to spring for new cylinders if they are on the loader. Part of the reason that there is some significant time involved is that the are two sets of seals. The first set, the obvious leakage, is from the ram rod that sticks out of the cylinder. As long as the rod is not scored, the seals are fairly easily replaced, some units use conventional o-rings and others have a compression packing. The power piston for the ram rod usually has o-rings to seal it. If the bore of the cylinder has gotten scored for some reason, sometimes it can be honed out, but most of the time the cylinder will not hold seals and needs to be replaced.

    You really do not need much in the way of special tools to take one the these cylinders apart. Most of the newer Kubotas have a quick disconnect on the loader to remove it, you can disconnect these snap type hydraulic fittings to isolate the loader. Unhook the two hoses from the cylinders and pull the two pins that hold the cylinder in place, stick a block of wood under the loader so that the cylinder is still in its range of travel, makes reassembly a lot easier. (Put some duct tape over the disconnected hoses to keep them clean, important). Next, clean up the cylinder to get rid of any oil or accumulated dirt. One end of the cylinder has a screw in fitting the same diameter as the cylinder, it has two slots in it for the "special" tool used to unscrew it. A pipe wrench will suffice for this operation. Once the fitting is loose, the rest of the guts pull out the end of the cylinder. You can then inspect the insides to determine its condition. The power piston is removable to get it out of the way so that the ram rod seal can be accessed. As with all things hydraulic, cleanliness is next to godliness. Kubota should be able to sell you the seal kit to do the repairs yourself. You will need to bleed the air out of the cylinders after you put them back, usually can do this by leaving the hose fittings loose enough to purge the air without spilling lots of fluid, but you will probably need to have some extra fluid to top off the system. Might be a good time to change the fluid if this tractor has a hydrostatic drive as the loader and transmission all run off the same pump.

    Dave
     
    Last edited: May 4, 2019
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  3. rkrochen

    rkrochen Well-Known Member

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    Yes hydraulic cylinders are generally quite easy to rebuild. Once you determine how to disassemble take it apart and clean then do a thorough examination of all the components to insure there is no scoring or damage, if so it may be cheaper to replace the cylinder. The top flange may be the hardest part to reassemble, sometimes it is tough to replace the seal. On reassembly make sure you prelude all the seals and take care reinstalled no components as it easy to knock a seal. Use quality replacement seals.
     
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  4. bulldogchesty

    bulldogchesty Senior Member

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    You can do it. Post pics.
     
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  5. BigblueC

    BigblueC Well-Known Member

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    Well Dave, I guess while you was tying that I got brave, actually I had a beer, but I took them apart with a big pipe wrench like you said. Everything looks really nice, clean and smooth in the bore and on the rod. Now I've got to decide if I'm going to attempt to replace the seals in the cylinder head and rod "pack", or pay for that to be done. It looks a little intimidating being so small on this 2.5 x 36" cylinder.

    @rkrochen How hard would you say it is to replace these seals with common garage/mechanic tools?
     
  6. rkrochen

    rkrochen Well-Known Member

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    Not hard you just need to take time. It all depends on the seal material. Some are quite hard and sometimes it helps if you place them in warm water first. You may need to work them into the groove, use a wooden dowel or round screwdriver handle to do this. Patience is the key. Also if I can do them so can you.
     
  7. Davea Lux

    Davea Lux Old Man with a Hat FCBO Gold Member

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    If you google "Rebuild Kubota Hydraulic cylinders, there is a you tube video that shows how to do it. Most Kubota's use the same design.

    Dave
     
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  8. Davea Lux

    Davea Lux Old Man with a Hat FCBO Gold Member

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    Just don't put the barrel of the cylinder in a vice. Clamp it at the lower mount point as that is solid metal.

    Dave
     
  9. BigblueC

    BigblueC Well-Known Member

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    Yeah, that's exactly what I did to open them up. So we're too late there. But I didn't clamp down too tight, just enough to stop slipping. But when I slid everything back together all seemed fine. No tight spots or anything.
     
  10. jct

    jct Senior Member FCBO Gold Member

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    Fingers crossed