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Hydraulic Cylinder Parts and Repairs

hydraulic cylinder with parts labeled showing barrel, cap, head, piston, piston rod, and clevis assembly


As we dive into hydraulic cylinder parts and repairs, it is best to first understand what is a cylinder, how they work, the parts that make up a hydraulic cylinder, and what applications use them. According to Wikipedia, a hydraulic cylinder is a “mechanical actuator that is used to give a unidirectional force through a unidirectional stroke”. What this means in layman’s terms is that there is a push and pull action that creates force and power, that is transferrable for mechanical use.

Hydraulic cylinders are typically powered by oil, but other liquids may be used as well. This pressurized oil gets pumped into the cylinder barrel and creates the power behind the motion. The flow may be controlled by a regulator to produce a consistent force on the application end or have a fixed pressure on the piston. Depending on the user’s needs, one option may be better than the other. Bigger pistons and barrels will increase the amount of force the cylinder can exert. Longer barrels and rods will increase the stroke or movement the cylinder can produce.

Hydraulic Cylinder Parts

A hydraulic cylinder is a fairly simple device with limited parts but each one is vital to the functionality of the part. The general parts mentioned above, and others, will be discussed in greater detail below. Our complete catalog will give more insight as too the different variations of parts from different manufacturers.

hydraulic cylinder barrel

Cylinder Barrel

The cylinder barrel is one of the main components to a hydraulic cylinder. These barrels are hollow tubes that house the piston and traveling fluids. The material used for it has to be strong enough to withstand the pressure being created inside itself or failure to do so will result in high-pressure explosions causing serious damage to the end-user and product.

hydraulic cyliner cap next to cylinder barrel

Cylinder Base / Cap

Cylinder bases, or caps, are located at the end of a cylinder and is connected to the cylinder barrel with an O-ring separation. Its role is to close off one end of the barrel so that pressure can be generated. The cap can be designed as an attachment to a trunnion, clevis, or just as an end piece. It is held on by threads, bolts, tie rods, or simply welded on.

hydraulic cylinder showing the cylinder head

Cylinder Head / Gland

A cylinder head, or gland, is put in place at the opposite end of a cylinder base. It completes the enclosure of a hydraulic cylinder and retains the pressure generated within the chamber. The main difference between the base and head is that the head has an opening for the piston rod to travel through when the part is in use. It is sealed to prevent pressure loss and oil leakage. The head is held in place by threads, bolts, tie rods, or can be welded on.

hydraulic cylinder piston and piston rod


The piston within a hydraulic cylinder is also a key component to its functionality. It separates the pressures generated by the base end and head end. They are sealed within the barrel with either O-rings or other sealing methods. This sealing allows the piston to move and travel in the barrel giving motion to the device. If the seal is broken, movement of the piston will be limited, decrease in pressure, or simply fail.

Piston Rod

Each piston has a piston rod that is attached by either threads, bolts, nuts, or welding. The rod is usually made from low friction materials like chrome so that the motion transfer can easily pass through the sealed head opening. The opposite end of the piston rod will be designed for application purposes with either an attachment or threaded for custom use. The piston rod is a main component to a hydraulic cylinder because it connects all of the motion and force generated from the cylinder to the machine element being used.

hydraulic cylinder parts disassembled

Other Parts

Other parts that play a role in a hydraulic cylinder include nuts, bolts, ring seals, and sealing agents. Depending on the manufacturer, there may be other added components to make the device exert more force, operate faster, or more efficient. Any other miscellaneous parts that go into a hydraulic cylinder can be found here.

Applications That Use Hydraulic Cylinders

Hydraulic cylinders travel in a linear motion which creates mechanical force that can be used in many applications. Two industries that have heavily incorporated them is the mobile and industrial automation industries. They can be found on backhoes, dump trucks, dozers, excavators, and loaders within the mobile industry. These applications require maximum power to do the work they are intended to do. In the industrial automation world, hydraulic cylinders are used for power and also their speed and reliability. Using them in an automated environment allows the end-user to bend steel through a programmed machine or create workholding force on an assembly line.

Hydraulic Cylinder Repairs

It is not uncommon to have to repair and replace parts within a hydraulic cylinder. The mechanical nature of the device allows for repairs to make them as good as new. They are the heart of a hydraulic system and bare much of the workload.

The Wear and Tear

A usual place for failure within a hydraulic cylinder would be the seals. This would result in loss of pressure and leakage.


Repairs should always be done by a trained professional. Our trained staff has over 20 years of experience and will do repairs with fast turn around times, plus offer warranty. For a free quote, email or call 586-741-5274 to speak with a professional technician. But if self-repairs are what needs to be done, then be sure to understand how a hydraulic cylinder works and what parts are used to make it.

With a basic understanding, the first step is to disassemble the hydraulic cylinder on a clean and open workspace. Any clutter will allow for misplacement of small parts such as nuts, bolts, and fittings. Start by removing the head, followed with the piston. Throughout this process, be careful not to tear seals or damage the piston or rod.

Diagnosing the issue through inspecting the parts will help you in repairing the hydraulic cylinder. This is where knowing the parts and how it works will come in handy. If hydraulic fluid has been leaking or pressure has dropped, then the root issue will most likely be the seals. Inspection of the piston and rod for scratches and dents will help narrow down the cause of failure in the part.

Once the root cause is determined, it is time to repair or replace components back to working order. When it’s time to rebuild, be sure to clean the parts. Water contamination will cause parts to fail so be sure to have dry parts. Rebuilding will be the reverse order of the disassemble process. Again, a trained professional is highly recommended and can be reached for a free quote at or 586-741-5274.

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