How to Change a Hydraulic Cylinder Packing


A hydraulic cylinder is a dynamic component. The rod end actuates back and forth in a linear action. Properly functioning seals are important to the function of a hydraulic cylinder, and almost every internal component has one or more seals. A packing is usually located in a specific part of the cylinder and is used differently than other seals like O-rings and backup rings. Packings on cylinders or located near the end cap on the rod end and help to seal against external leakage as the rod extends out of the cylinder's barrel. Most of the other cylinder seals are designed to prevent internal leakage.

Things You'll Need

  • Bench vise
  • Wrenches
  • Cylinder seal kit
  • Seal removal tool
  • Torque wrench
  • Emery cloth
  • Hydraulic fluid


  • Drain the cylinder's hydraulic fluid. You will have to open the cylinder's fluid ports if they have hydraulic caps or plugs screwed onto them. Then drain the cylinder fluid from the ports into a bucket or other container.

  • Remove the end cap components. Some cylinders are secured at the rod end with an end cap, a gland nut or both. Various other retaining mechanisms can also be used, such as lock wires or snap rings. Study the rod end of the cylinder to determine what type of tool you'll need to access the interior of the cylinder. Then clamp the cylinder securely in a vise and remove the retaining device or end cap. You may need a gland wrench, snap ring pliers or other special tool.

  • Pull the piston rod straight out of the barrel. The packing will be secured around the rod, and you'll have to disassemble the entire piston rod to remove it. This is not a problem, since it is recommended that you replace every cylinder seal every time you perform internal maintenance on a hydraulic cylinder.

  • Clamp the piston rod onto a vise with soft jaws or with some protective barrier between the vise jaws and the polished cylinder rod. A rag will due if a soft-jawed vise is not available. New packings can be damaged by scratches or scores on the rod's surface.

  • Unscrew the nut or bolt at the very opposite end of the piston rod that holds the piston on. A standard wrench or socket will do the job.

  • Slide off all the parts from the piston rod, even though the packing is one of the last parts that will come off. Remember, you will reseal everything.


  • Remove all the seals from each internal component. O-ring type seals may have to be removed with a seal removal tool, or seal pick. The cylindrical packing will simply slide off of the cylinder.

  • Clean all the polished surfaces of all cylinder parts and dry them. Use a safe, petroleum-base solvent, if needed.

  • Inspect the clean parts for scratches and cuts. They could damage the new seals on installation or operation of the cylinder. Replace any badly damage parts. You can smooth out slightly rough areas by buffing with an emery cloth.

  • Install new seals on every applicable part. You can purchase a cylinder seal kit for most hydraulic cylinders that contains every seal in the cylinder. Install the new packings in exactly the same position and orientation as the old packings. Though it is possible to replace only the packings, it is not recommended. And since you must disassemble the entire piston to remove the packing, it's not much more work to reseal the entire cylinder.


  • Install the parts back onto the piston rod so that they are positioned and configured in the same manner as they were before disassembling the piston rod assembly. Install and tighten the piston nut last.

  • Moisten newly sealed and assembled components with hydraulic fluid and insert the entire piston rod back into the cylinder barrel.

  • Reinstall gland nut, end cap, snap ring or other retaining device to secure the rod in the cylinder.

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  • Photo Credit pump image by Aleksander Nordaas from
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