How to Rebuild Hydraulic Cylinders

This step by step guide of How to Rebuild Hydraulic Cylinders is meant to show the simplest way of how to repair leaking cylinders. Once your cylinder has started leaking and losing power it needs to be either replaced or better yet repaired.

There is a whole lot of reasons why a cylinder needs repair, simplest and most common necessary repair is the repacking of the seals. Although a pretty simple operation, it does require at least some mechanical intuition. If you do not feel comfortable getting your hands dirty than it might be better to just let our Hydraulic Repair Department do the dirty work and repair your cylinder right the first time.

If your comfortable working with tools and want to repair your cylinder by yourself than just follow this guide and you should have the cylinder up and running in no time.


Step 1. Disassembly


After you have the cylinder taken off the machine you are ready to take it apart. You will need to take the piston out of the cylinder in order to diagnose what is wrong with it.

The first step starts with removing the cover end of the cylinder from the shaft side. The cover is removed by either unscrewing it or by removing the bolts. Once the cover is removed you are ready to remove the piston, loosen the input valves (where the hydraulic fluid is pumped in) to lessen the pressure and slide the piston shaft out. Once you have the piston shaft out of the cylinder detach the piston from the shaft.


Step 2. Inspection


Once you have the piston disassembled from the cylinder you need to perform a visual inspection to figure out the problem. If you find that the piston shaft is bent or the Cylinder Bore is scratched than the repairs require a Qualified Hydraulic Repair Shop (Like Ours) to do the repairs.

Your Hydraulic Cylinder might require the manufacturing of a new shaft, or the Honing of the cylinder bore in order to remove the scratches and gouges and to restore the seal. These operations require specialized machinery and ability which most likely are out of your league. If the shaft and the bore are fine than most likely the seals are the problem. If any of the seals on your cylinder are damaged than the hydraulic fluid will leak and you will lose the necessary pressure.


Step 3. Repacking the Seals


In order to repack the seals you must first obtain a seal kit for your particular cylinder. The seal kit provides all the necessary seals and o-rings that are needed to replace the damaged ones. It is always a good idea to try get repacking instructions for your cylinder from the manufacturer to help you along the way.

Begin by carefully removing the old seals be sure to remember which seal goes where. Once you have the old seals off, match the new ones to the old ones and carefully put the new seals in place. This process is probably easier than it sounds, all you need to do is replace the new seals in place of the old seals exactly as they were. You must be very careful not to damage the new seals in any way because you will just end up where you started from.


Step 4. Re-Assembly


Now you are ready to reassemble the piston back into the cylinder. First oil all the seals up with a bit of oil or hydraulic fluid and gently slide the piston back into the cylinder. If you are having a hard time pushing the cylinder back in because of pressure, make sure that the input valves are loosened in order to let the air out.

You should be able to easily move the piston back and forth within the cylinder. If however it is very tight, you might have remove it again and make sure that the seals are sitting correctly and in the correct place. Once the piston is in you can proceed with putting the cap back on, just reverse what you did to take it off.






I recommend testing the cylinder before you reattach it to your equipment. Hook up the hydraulic hoses and check for any leakage. If you did everything correct you will have a like-new cylinder that should work well for months.

Of course using a qualified shop like ours, ensures that everything will be done right, and with our Cylinder Honing option we can extend the life of your cylinder to even longer.

If you don't feel confident in performing the repairs yourself, or your cylinder requires more than just the seal repacking do not hesitate to Contact Us Directly for a Quotation.


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