How to Rebuild a Welded Hydraulic Cylinder


Hydraulic cylinders have two basic construction types: welded construction and tie rod construction. Welded hydraulic cylinders have end caps welded directly onto the cylinder barrel. Tie rod cylinder end caps are held together with threaded rods. Welded hydraulic cylinders can be more compact that tie rod cylinders, but the internal mechanics are identical. Disassembling a welded cylinder is slightly different than taking apart a tie rod cylinder, but once that is done, you will have to replace all the internal seals to rebuild any hydraulic cylinder.

Things You'll Need

  • Bench vise
  • Wrenches
  • Cylinder seal kit
  • Torque wrench
  • Seal removal tool


  • Remove any hydraulic plugs from the cylinder's fluid ports and drain all the cylinder's hydraulic fluid.

  • Clamp the cylinder securely into a bench vise and pull the piston rod all the way out.

  • Remove the gland nut, snap ring or spanner nut with the appropriate tool. This retaining device holds the entire piston rod inside the cylinder.

  • Pull the piston rod completely out of the cylinder and secure it in a soft-jawed vise.

  • Unscrew the nut or bolt that holds the actual piston onto the rod, then remove the piston and the gland, if applicable. Remove any other parts attached to the piston rod, as well.

  • Remove the seals from all the parts with a seal removal tool, and wipe all the parts clean. Clean them with a petroleum-based solvent if needed, and inspect them for gouges and scratches. Replace any damaged parts.


  • Install new seals onto every applicable part from the cylinder seal kit or rebuild kit.

  • Assemble the parts back onto the piston rod. Consult a diagram of the cylinder parts or install the parts in the reverse order of how they were removed. Install the nut or bolt that holds the piston last and tighten it to its required torque with a torque wrench.

  • Insert the piston rod assembly into the cylinder barrel and secure it by screwing in the gland nut or securing the snap ring or other retaining device.

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