When to Bleed Hydraulic Cylinders

Hydraulic cylinders are devices made of a series of interconnected tubes that pressurize liquid or gas to create motion. They are often used to power pumps, fans, and motors, but can also be used to move objects or fluids in a controlled manner. When a hydraulic cylinder begins to malfunction, one common fix is to bleed the device. Bleeding your cylinders will help free up any debris that may be blocking the pistons and valves. To learn more about bleeding hydraulic cylinders, read on as we discuss this vital form of maintenance.

What Are Hydraulic Cylinders?

Hydraulic cylinders are used in many different applications, including in high-powered vehicles like aircraft and military automobiles. Coming in a variety of shapes and sizes, they can be made to fit tight spaces or help power enormous operations. In addition, hydraulic cylinders may use several different fluids, including water, mineral oils, synthetic fluids, vegetable oils, and emulsions. Combining a system of interconnected pipes with pistons and valves, hydraulic cylinders are capable of generating a large amount of force using pressure and release.

What Are Bleeding Hydraulic Cylinders?

If there is an issue with your hydraulic cylinders, it is often necessary to bleed them first before conducting maintenance. Bleeding your cylinders helps free up any debris trapped in the system and should be done regularly to maintain a working assembly. There are a few different ways to bleed a hydraulic cylinder with each system having a designated method. The most common method is to use a syringe; some hydraulic cylinders are designed with a plunger fit to the inside of the machine for this purpose. During the bleeding process, the plunger is pushed up and down, and when it reaches the bottom, the fluid is forced out through a fitting and onto the ground.

Other types of cylinders can be bled using a pressure bleeder or a vacuum bleeder. The pressure bleeder uses air to push the fluid out. To use this type of bleeder, you must first raise the pressure in the machine by turning up the gas or oil valves. Then, the bleeder tube must be connected to the fitting on the machine. Once the bleeder tube is in place, the bleed valve should be opened, and then the bleeder tube can be pressurized by pumping air into it until the gauge reads 100 psi. For the last step, you must then close the bleed valve and wait until the gauge reads 0 psi before releasing the air pressure. Conversely, the vacuum bleeder uses vacuum suction to pull fluid out. Nevertheless, vacuum bleeders are similarly hooked up to the machine fitting.

When to Bleed a Hydraulic Cylinder

If there is hydraulic fluid leaking from a hydraulic cylinder, it is most likely time to bleed the system. Here are four specific issues that typically require bleeding your hydraulic cylinder:

1)    A bypass valve has been opened inadvertently and is allowing fluid to escape from the cylinder into the system.

2)    The cylinder seal has failed, allowing air and fluid to mix and create leaks.

3)    The piston has become stuck in the cylinder, preventing it from moving, creating a pressure buildup.

4)    The hydraulic system has been damaged in some way and needs to be repaired or replaced.


Bleeding cylinders is a crucial maintenance task that should be done regularly and whenever repairs need to be made. During your operations, you find yourself in need of a replacement part, we encourage you to make use of our vast online catalogs on ASAP 3Sixty. As a leading supplier of hydraulic cylinders and their associated components, we guarantee solutions to fulfill all your strict timelines and operational requirements. Begin procuring the parts you need today with unbeatable quality and savings when you choose ASAP 3Sixty as your strategic sourcing partner.


Recent Twitter Posts

asapSemiconductor's Certifications and Memberships

Thanks for Visiting!

If You’d Like to Stay Updated On Our Latest Promotions, You Can Download the ASAP Semiconductor App from the App Store and Google Play Store.

Request for Quote

We use cookies to ensure that we give you the best experience on our website. If you continue to use this site we will assume that you are happy with it.