Cylinders Inc.
Certified women-owned business
How to Repack a Hydraulic Cylinder: Step-By-Step Guide & Tips

How to Repack a Hydraulic Cylinder: Step-By-Step Guide & Tips


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?

hydraulic cylinder 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

how to repack a hydraulic cylinder

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.

5 Additional Tips for Repacking & Rebuilding Hydraulic Cylinders

Hydraulic cylinders are important components of heavy machinery and equipment and can’t be ignored. Here are five more tips for repacking and rebuilding hydraulic cylinders.

Inspect Your Cylinder Thoroughly After the Disassembly

repack a hydraulic

Before repacking or rebuilding your cylinder, it's important to inspect it properly after disassembly. This will help you identify any parts that need to be replaced or repaired before proceeding with the rebuilding process. Any visual defects found during the inspection require prompt attention. You don’t want to reassemble the cylinder and then discover a problem that you could have fixed prior. Replace any damaged parts before rebuilding the cylinder. By inspecting your cylinder very thoroughly after disassembling it, you can save yourself from a lot of headaches in the future, not to mention a lot of time and money.

Double-Check Whether You Have All the Tools

The hydraulic cylinder rebuilding process requires specialized tools, so it's important to ensure that you have all the tools required before starting the process. Missing an essential tool can cause a delay and put a halt on your project. Some of the typical tools required include the seal installation tool, hydraulic cylinder rod scraper, pick and spring puller, and hydraulic cylinder action tester. Verify that all the tools are present and that they are in good condition. If any tool is not working properly or needs cleaning, you should address that before getting started. Otherwise, you may damage something.

Resize the Seals

If you're repacking the cylinder, it's important to resize the seals to a precise fit. The diameter and cross-sectional shape of the seal are critical, as they directly affect the cylinder's performance. The piston's diameter determines the size of the seal, so it's important to choose the right size. Resizing seals is a task that requires a high degree of accuracy, so it's best to seek help from a professional if you're not sure how to go about it. If your seals are improperly fitting, you may end up with excess oil and fluid build-up, which can damage the piston rod bearings and possibly corrode the entire hydraulic cylinder.

Never Skip the Testing

After rebuilding or repacking the cylinder, it's important to perform a cylinder action test to ensure that it's performing optimally. This is essential because it determines the cylinder's performance and safety. If you detect any problems, you can make the necessary repairs before placing the cylinder back into service. A cylinder action tester will simulate the cylinder's operation and deliver real-time performance data. An easy DIY test is the end-of-stroke bypass test. All you need to do is pressurize the cylinder with oil and inspect for any oil leakage near the seal at the bottom of the cylinder’s stroke.

Consider Going to the Professionals

Not everyone has the expertise to rebuild hydraulic cylinders, especially if you lack the proper tools or knowledge. If you're unsure of what to do or how to proceed, consider seeking the services of a professional that handles hydraulic cylinder repairs. Professionals have the expertise, tools, and experience to identify problems, repair or replace faulty parts, resize and repack the cylinder, and ensure the cylinder's safe operation. By going to a professional, you will save time and money and avoid a lot of stress, and it's best to trust the expertise of someone who knows what they’re doing.


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!

Cylinders inc. team



Contact us

Time to Repack Your Hydraulic Cylinders?

Proper repacking is essential for maintaining the efficiency and reliability of your hydraulic cylinders. Trust our skilled technicians to expertly repack your cylinders using top-quality seals and best practices.

Schedule Cylinder Repacking Service

Request Your Hydraulic & Pneumatic Cylinder Repair


Request Your Cylinder Repair Today

Have a question about our pneumatic cylinder repairs? Contact Cylinders, Inc. to find out more about how our experts can help, or schedule your repair service today!

Country: unknown
Thank you! Your submission has been received!
Oops! Something went wrong while submitting the form.