Changing the seals on an automotive lift hydraulic cylinder.

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Hydraulic cylinders are critical components in various industries, providing linear force to power machinery and equipment. Over time, the seals in a high-pressure hydraulic cylinder may wear out or develop leaks, compromising the cylinder’s performance. In this instructional blog, we will guide you through the process of changing seals in a high-pressure hydraulic cylinder, ensuring the longevity and efficiency of your equipment.

Note: The following instructions are only a general guideline. It is essential to consult the manufacturer’s documentation and follow their specific guidelines for your hydraulic cylinder model.

Tools and Materials Needed:

  1. Wrenches (appropriate size for cylinder fittings)
  2. Soft-faced hammer or mallet
  3. Chain vise grip
  4. Work bench with a vise
  5. Pry bar, small picks
  6. Seal installation tool (click to amazon link)
  7. Clean, lint free rags or towels
  8. Replacement seals (specific to your hydraulic cylinder model)
    • You can find seals for your lift on our site using your model number or by calling us.
  9. Hydraulic fluid
  10. Safety gloves and goggles

Parts of a hydraulic cylinder

Parts of a cylinder from

Step 1: Prepare for the Seal Replacement

  1. Ensure that the hydraulic system is fully depressurized and turned off to prevent any accidental movement or discharge of hydraulic fluid.
  2. Follow Lock out Tag out procedures.
  3. Position the hydraulic cylinder in a way that allows easy access to the seals, either by detaching it from the equipment or positioning it for accessibility.

Step 2: Remove the Cylinder from the Equipment (if necessary)

  1. Follow the manufacturer’s instructions to safely remove the hydraulic cylinder from the equipment. This may involve disconnecting hydraulic hoses and removing mounting brackets.
  2. Support the weight of the any attached components before disconnecting the cylinder.
  3. Support the cylinder using appropriate equipment, such as a hoist, engine crane or sturdy workbench. It’s helpful to have another person or two with you to help.

Step 3: Disassemble the Cylinder

  1. Using the appropriate wrenches, carefully disconnect the hydraulic lines from the cylinder fittings, ensuring that any residual hydraulic pressure is safely released.
  2. Remove any mounting brackets or hardware securing the cylinder housing.
  3. Remove the cap to gain access to the inside of the cylinder. This is one of the difficult parts in the process, so start by taking a good look at the cap and determine the best way to disassemble it.
    • Most caps are threaded. They may or may not have installation flats that you can use with a large wrench. If not, you will need a chain wise grip.
      • TIP Place the cylinder in a vise to retain the cylinder tube while loosening the cap (Use rubber pads or rags to protect the cylinder tube, do not overtighten as this can damage the wall). Heat may be required to loosen the threads.
    • Other caps may be retained by a circlip or wire rod inserted into a grove. For wire rods, find the end of the rod and guide it out of the window in the cylinder tube. Rotate the cap to remove the rod.
  4. Once the end cap is removed, carefully slide out the cap, rod and piston assembly, ensuring not to damage any components or score the wall of the cylinder tube.
  5. Locate and remove the old seals from the piston assembly using small picks. Take note of the seal orientation for correct placement during reassembly.
  6. Removal of an internal wiper or seal from the cylinder cap can difficult. Use small picks or a cylinder seal removal tool like this one. Hydraulic seal tool.

Step 4: Install the New Seals

  1. Thoroughly clean the cylinder bore and piston assembly using clean rags or towels to remove any debris or residue.
  2. Apply a small amount of hydraulic fluid to the new seals to aid in installation.
  3. Install the new seals into their respective grooves, ensuring they are properly seated and oriented according to the manufacturer’s guidelines.
  4. Use the cylinder seal tool to reinstall seals into internal groves of the cap.

Step 5: Reassemble the Cylinder

  1. Reinsert the piston assembly into the cylinder bore, taking care not to damage the new seals on threads or sharp ends of the cylinder tube. Protect threads with a thin plastic sheet if necessary.
  2. Apply a light coating of hydraulic fluid to the cylinder bore and piston assembly for lubrication.
  3. Carefully place the end cap back onto the cylinder and secure it with the appropriate hardware.
  4. Reconnect the hydraulic lines to the cylinder fittings, ensuring proper tightening to prevent leaks.

Step 6: Test and Reinstall the Cylinder

  1. Reattach the hydraulic cylinder to the equipment, following the manufacturer’s instructions for proper mounting and alignment.
  2. Reconnect any hydraulic hoses and ensure all connections are securely tightened.
  3. Slowly pressurize the hydraulic system, checking for any signs of leakage or abnormal operation. Bleed the system as per manufacturer instructions.
  4. Monitor the cylinder for a period of time to ensure the new seals function correctly and maintain a proper seal.

This is a basic guideline meant to help you decide if taking on the job of replacing seals on your hydraulic cylinder is right for you. Regularly inspecting and replacing worn or damaged seals will help maintain the performance and reliability of your hydraulic system. Remember, safety should always be a priority, so wear appropriate protective gear and consult the manufacturer’s documentation for specific guidelines pertaining to your hydraulic cylinder model. If you are not comfortable with this job, it may be wise to have the cylinder rebuilt by a professional.

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