Whether you are a small farmer or have a ranchette, you probably own a tractor or some other type of equipment which utilizes a hydraulic cylinder for some function or another. Most modern tractors, both large and small, use a hydraulic cylinder for the power steering system. These same types of hydraulic cylinders are used extensively on many types of combines and cultivation equipment. Eventually the seals will start to leak oil a little but there comes a time when the amount spent on hydraulic oil makes it imperative to rebuild the cylinder. This article takes you through the steps needed to breakdown the cylinder and replace the o-rings and other seals on the piston and gland.

Before you begin

There are so many different types of hydraulic cylinders manufactured for all kinds of functions and machines that you should try and locate the correct repair or rebuild kit before starting your disassembly. The parts numbers are usually stamped into the end cap or on the outside of the cylinder. If your particular cylinder is a major make, such as a Case, John Deere, or other well know brand, you simply go to the local dealer and buy or order the kit you need. You can also get a print out of the parts diagram which may prove very helpful in the rebuilding process. You may have to order the parts on the internet but as long as you have the parts numbers this should be no problem. It is always best to have the parts when the process begins to compare the new and old parts.

When the hydraulic cylinder is used for raising or lowering heavy objects or for other weight bearing purposes, always brace or otherwise support the weight with jacks or blocks to prevent injury to yourself or the equipment. Some of these pieces weigh quite a bit so be aware of the danger of crushing fingers or hands. Perform all parts of the operation slowly and carefully. Safety is foremost in this type of repair.

Hydraulic cylinder disassembly

The hydraulic cylinder being rebuilt in this article is one of a pair used for raising the bucket on the front end loader of a Case 580C backhoe. I have already rebuilt several of the other hydraulic cylinders on the backhoe part of the machine. Each cylinder, or set of cylinders, has a different gland and seal kit. I do not have all of the correct wrenches for each gland so I make my own. Eventually I will have a wrench for each cylinder, or so I hope. The glands have four holes used for unscrewing them from the cylinder.

The tool I constructed here uses two prongs of spring steel cut from a spring tooth out of a peanut combine. Soft steel may work but not on a large cylinder.Measure the distance between two of the opposite holes and place the two prongs the same distance. A cutting torch and welder is the best tools a small farm or homeowner’s shop can possess. Blow the holes through, insert the prongs and weld tight. Works well and costs very little, not too pretty though.

Before doing anything be sure all pressure is released from the cylinder. Loosen or remove the hydraulic lines on each end of the hydraulic cylinder as this will allow all pressure to escape. You may be able to unscrew the gland without removing either end of the hydraulic cylinder assembly from its end connections. In this case we needed the room so we pulled the pin from the piston rod end. Using the new tool, the gland is unscrewed from the hydraulic cylinder. In some cases a slight tap or bump with a hammer may be applied to the tool to break the gland loose. Once loosened, the gland should unscrew easily and pull away from the hydraulic cylinder if there is room on the piston rod.

With the gland removed, pull the piston rod from the cylinder. Large hydraulic cylinders may have to be supported to keep them straight while removing the piston rod. A winch is sometimes used for large cylinders but is not required in most cases. Try to keep the piston rod from falling into the dirt or against other metal objects when it pulls out of the cylinder. Protect all parts, such as the fine threads inside of the cylinder from any damage, this is a very important and potentially costly precaution. Do not hurry!

When the piston rod is free put the rod end back into its pin connection and unscrew the retaining bolt which holds the piston to the rod. In extreme cases this bolt may have to be heated if a thread locking substance has been used in a prior rebuilding process. Try not to heat the piston no more than necessary and this should work well. Place the parts in order and take a photo or two for later reference if needed.

Reassembly and reconnecting the hydraulic cylinder

Most hydraulic cylinder rebuild kits will furnish a diagram for correct installation purposes so look this over well before replacing the o-rings and seals in the gland and piston. All will be slightly different from each other so you will have to identify each new seal and o-ring. Some of these seals are very thin and may be damaged if not installed evenly.  In some cases the old seal may be used as an aid to reinstalling the new piece. Be careful to put these in very evenly or they may be damaged in the process. Examine each o-ring in each groove and remove and install these one at a time to keep from getting confused as to correct placement. Clean each groove and seat carefully before replacing with the new part.

Reverse the process when reassembling the piston to the rod using a thread locking adhesive when replacing the piston rod bolt. Oil all parts well and use a piece of wood on the rod end if needed when tapping the piston back into the cylinder Do not use a thread locking substance on the gland threads when screwing the gland back into the cylinder. Replace the hydraulic lines and test for leaks around the new seal. Follow the same basic procedure for most cylinder types. Good luck!