How to Repair a Hydraulic Cylinder

In this article, we are going to teach you the best way to repair a hydraulic cylinder - from your own garage. By repairing cylinders yourself, you can save money, resume work much faster, and learn to appreciate hydraulics as much as we do here at Curry Fluid Power.

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Hydraulic cylinders are typically long lasting pieces of equipment. Occasionally, they will fail due to oil contamination, seal breakage, or rod imperfections caused by wear over time. To fix a simple, double-acting cylinder found on common earth movers such as loaders, excavators, graders and bulldozers, follow these 12 simple steps.

Step 1: Gather the required tools.

Before we servicing the unit, you will need access to the following items:

• Pipe wrench or Spanner Wrench
• Flashlight
• Bucket
• 9” Scribe Pick
• Cresson Wrench (Impact)
• Vice
• Caliper
• Grease, Oil, Lube (Super Lube)
• Fine Paper, Crocus Cloth, or Scotch Brite Pad

Step 2: Check the outside of the cylinder for obvious damage.

Step 3: Use the pipe wrench to remove plugs and drain the oil. On most cylinders, the plugs can be found on the end. For double-acting cylinders, plugs will be located on both ends. After removing the plugs, turn the cylinder over and drain the oil.

Step 4: Use a vice to break the gland loose. The gland is Check the barrel for any obvious imperfections. DO NOT place the cylinder rod in the Vice. Any scratches or scrapes on the rod itself will nick the seals overtime, making them deteriorate much faster. Seals are used to seal gaps between different parts of the cylinder to prevent oil leakages and reduce friction.

Step 5: Remove the Gland. Pull the Rod from the barrel.

Step 6: At the second location, remove the piston nut using a Cresson wrench.

Step 7: Slide piston and gland off of the rod. Check the piston nut, gland, and rod for rust or imperfections. Use an emery cloth, a fine stone, or even some sandpaper to smooth out any imperfections. If parts are damaged beyond repair, new parts can be machined at our machine shop. Simply measure the length and diameter of your cylinder and contact our technical inside sales team.

Step 8: Remove Seals. Use your pick to remove seals from the gland. Seal categories differ by manufacturer. However, the six general kinds of seals are Gland Seals, Pin Seals, Rod Seals, Piston Seals, Wear Bands and Wipers. See the chart below for a demonstration of seal chart types.

Step 9: Identify the source of the failure. Check for punctured seals, rod imperfections, barrel scrapes, and signs of corrosion. Check the packing, or outer seal, for damage. This could be a sign of a barrel imperfection.

Step 10: Identifying Seals. Chances are, the source of the failure is due to a punctured seal. To identify the kind of seal that must be replaced, measure the rod first. The length of the rod will tell you if the seal is metric or standard. Next, using a caliper, measure the thickness of the seal. After obtaining the proper measurements, use the cylinder make and model as well as the seal dimensions to find the proper replacement in the Seal Catalog. Serial and/or model numbers for a cylinder are typically located at the base end of the cylinder.

If you are pressed for time, you can always contact our inside sales team and let us order the seals for you.

Step 11: Begin the rebuild process. Apply Seals. Always place the lip of the seal towards the pressure of the oil. Reassemble the cylinder. Gently cycle your equipment a couple of times to bleed air out of the cylinder before running at full capacity.

Step 12: Check the cylinder for oil leaks after operation.