How to install a hydraulic piston seal

Written by michael signal
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How to install a hydraulic piston seal
A cylinder's actuating rod is attached to a piston inside the cylinder. (hydraulic lock mechanism image by green 308 from

A piston provides operating surface area for hydraulic fluid inside a cylinder. The larger the piston, the more force can be applied to it. Even if the component the piston rod attaches to and moves is far away from the piston itself, it's still the piston that is the workhorse of a hydraulic cylinder. Worn and damaged piston seals can cause internal leakage within the cylinder. This will cause the piston to operate improperly or less efficiently.

Skill level:

Things you need

  • Piston seals
  • Small plastic tie
  • Spring compression tool
  • Hydraulic fluid

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  1. 1

    Clean the piston and inspect it for nicks, cuts or gouges. Smooth out any rough areas by polishing with an emory cloth. Replace the piston if it has deep gouges or cuts.

  2. 2

    Pull the new piston seal around the piston. Some pistons use more than one seal. Pull them over the piston and push them into the recessed areas of the piston. If the piston uses multiple split rings, make sure the splits face opposite directions. If it is hard to push the seal into its recess, you may have to make a special tool to pull the seal. You can do this by looping a small plastic tie around the seal and then pulling.

  3. 3

    Lubricate the seal with hydraulic fluid. Shrink the seal if it is loose. Do this by inserting the seal into a seal compression tool and tightening the tool. Some seals may also shrink to their original sizes after resting for eight hours.

  4. 4

    Push the piston into the cylinder using the seal compression tool as a guide or remove the tool completely if the seal has compressed enough to fit safely into the cylinder.

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