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The Complete Guide on How to Repack a Hydraulic Cylinder
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The Complete Guide on How to Repack a Hydraulic Cylinder


Hydraulic cylinders are costly to replace. At Cylinders, Inc., we always opt for repair and only suggest replacement as a last resort. Naturally, regular hydraulic cylinder maintenance and repacking hydraulic cylinders prolong a cylinder’s lifespan.

Knowing how to repack hydraulic cylinders is an uncomplicated process and easy process to learn. In this guide, we explain exactly how to do it, so you can take better care of your equipment.

Why Do You Want to Repack Your Hydraulic Cylinder?

Repacking hydraulic cylinders is part of regular preventative maintenance, as most eventually begin to leak oil from their seals. When you repack a cylinder, you ensure it keeps working in optimal condition. It’s also more eco-friendly than purchasing a new one.

As a side note: When cylinders start to leak, it is more cost-effective to repair components than replace the entire thing. The process of repacking a cylinder is relatively straightforward with the right tools:

  • A repacking kit: These contain parts and components to replace damaged components.
  • Hydraulic oil: It’s important to have a new supply of oil, as contaminated oil can damage new packaging.
  • A container to catch used oil
  • A clean workplace: Sometimes oil spills occur, regardless of how diligent you are. Always choose an area that won’t be affected by oil spills.

How Do You Know That Your Cylinder Needs Repacking?

Typical signs your cylinder requires repacking include; increased oil leaks, increased levels of difficulty in moving a part of lifting heavy loads, and implements leaking down at a faster rate than usual. But, before repacking a hydraulic cylinder, we advise testing it first.

  1. Fill both of the cylinder’s sides with hydraulic fluid.
  2. Move the cylinder through its full stroke several times to expel all air.
  3. Pressurize the cylinder fully extended and check for leaks.
  4. Retract the cylinder and hold to check for further leaks.
  5. Run an internal bypass test. To conduct this, retract the cylinder and hold it with the base port line removed and capped. Different types of seals have various levels of acceptability when it comes to leakage. In general, you will see the cylinder rod extend as fluid fills the chamber and bypasses the piston seals.

Tools and Equipment Required for Hydraulic Cylinder Repacking

You will need these tools to successfully repack a cylinder:

  • A seal kit
  • A rubber mallet
  • Screwdrivers
  • A punch
  • Pliers
  • A spanner
  • A wrench
  • Allen wrenches
  • Emery cloth
  • A torque wrench

Prepare for Repacking

You’ll want to ensure the old parts are the same shape, size, and type as the new ones. If your cylinders are used in equipment that raises and lowers heavyweight, then brace the support weight with jacks or blocks to prevent accidental injury to you and costly damage to the equipment.

Clean off the unit, detach hoses, and plug all ports before disconnecting the hydraulic cylinder, after which you will need to open all ports and drain all fluid.

During preparation to repack a cylinder, make sure that:

  • The rod is straight
  • The inside of the barrel surfaces display proper cross-hatching
  • There are no scars or gouging
  • The chrome plating on the rod is undamaged. If there is a slight nick, make sure there are no raised burrs.

How to Repack a Hydraulic Cylinder in 8 Steps

Here’s how to repack a hydraulic cylinder in eight simple steps.

  1. Pull the control lever back and forth several times to release all pressure from within the cylinder.
  2. Loosen and remove hydraulic lines from the cylinder to allow the last bit of pressure to escape.
  3. Once you’ve secured the cylinder, you can remove the pin from the end of the rod. Each cylinder is different depending on the manufacturer. Some are bolted, which requires the insertion of a special tool to turn the gland where the rod exits the cylinder. Make sure to research this procedure beforehand and that you have the appropriate tool for it.
  4. Remove the piston rod from the cylinder. Keep it free of contamination caused by touching other metals or coming into contact with dirt. You also want to make sure the fine threads inside the cylinder are undamaged during removal, as this could result in a costly repair.
  5. Replace seals and o-rings on the piston and gland one at a time. This minimizes confusion and incorrect placements. This is absolutely critical because some seals are very thin and can be damaged if not evenly installed. Each groove should be clean, and debris free before installing the new part.
  6. Reverse the first four steps and reassemble the piston to the rod. Use a thread locking adhesive when replacing the piston rod bolt.
  7. Reinsert the gland into the cylinder, but do not use any thread locking substance on the gland threads.
  8. Replace all hydraulic lines and test for leaks around new seals.

Note: When repacking a hydraulic cylinder, there are different ways to hold the rod to the piston. A threaded rod can either have the piston directly attached, or with just a nut, or a nut and bolt can hold the piston in place.

You also might want to take photographs of each step of the process to ensure all the parts are in order.


If you still feel unsure of the process or would prefer to hand over your cylinder to professionals, then reach out to us at Cylinders, Inc. We conduct comprehensive cylinder audits to see if they need repacking or more serious repairs. Our professionals and fully equipped shop at Cylinders, Inc are adept at handling repairs of all shapes, sizes, and brands. We promise to repack your cylinder and get it operating like new!

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