How To Bleed A Hydraulic Cylinder

Update:Feb 28, 2019

From time to time the hydraulic cylinder in your vehicl […]

From time to time the hydraulic cylinder in your vehicle may contain too much hydraulic fluid. This can result in too much hydraulic pressure being created that could cause damage to components in your vehicle that use the fluid pressure. Therefore, you may need to occasionally bleed the cylinders and lines in order to keep hydraulic pressure at appropriate levels. So, this step-by-step guide will show you how to bleed your vehicle's hydraulic system.

Prepare Your Vehicle

First, make sure to disconnect the negative battery cable for the post on your car's battery. This is to prevent electrical shock while working on your car. Then, jack up your car and place it on jacks stands.

Locate the Bleeder Valves

The location of the bleeder valve(s) for your car's hydraulic system will very depending on the make and model vehicle you own. Therefore, you may want to refer to your car owner's manual or refer to a car repair manual made for your particular vehicle. Once you have located the bleeder valve(s), you can proceed.

Bleed the Hydraulic Lines

First, bleed the hydraulic line that's farthest from the master cylinder of the hydraulic pump, and then continue to bleed the other lines. Bleeding the hydraulic lines will help to relieve pressure on the entire hydraulic system, and also make bleeding the master hydraulic cylinder or your brake system easier.

Remove Hydraulic Fluid Reservoir Plug

Locate the hydraulic fluid reservoir plug on the master cylinder. Remove it and clean it with a towel or rag and place it somewhere where you can easily find it.

Bleed the Master Cylinder

Locate the bleeder outlet valve screw on the master cylinder, and then attach one end of the plastic tubing to it. Choose a piece of plastic tubing that fits tightly around the valve as to avoid air leaks being allowed into the master cylinder. Then, place the other end of the plastic tubing into an empty soda bottle.

Next, you can initiate the hydraulic piston a few times to initiate the flow of fluid. Or, if you're trying to bleed the hydraulic brake lines of your vehicle, you can simply pump the brake pedal a few times. Finally, open the bleeder outlet screw valve and the fluid should begin to flow into the empty soda bottle.

Close Master Cylinder Bleeder Valve

Tighten bleeder outlet screw valve once all of the pressure has been relieved.

Refill the Hydraulic Master Cylinder

Pour the fluid from the soda bottles into the refill bottles, and then use them to refill the master cylinder. Be sure not to fill the cylinder too much, or you will need to bleed the system again. Finally, replace the reservoir cap or plug.

When bleeding the hydraulic cylinder or lines, never bleed all of the fluid from the system. Always make sure that a minimum level of fluid remains in the system even when bleeding it.


Lower the Vehicle

Remove the jack stands and lower the vehicle with the car jack.