How to Fill the Hydraulic Fluid in a Forklift

by Matt Kester

Hydraulic fluid is the lifeblood of a forklift. Forklifts rely on hydraulics for their lifting abilities as well as steering. It is important to maintain the proper level of hydraulic fluid in a forklift's reservoir. An inadequate level of hydraulic fluid will decrease a forklift's lifting and steering abilities. An overabundance of fluid, on the other hand, can lead to other problems, such as leaks and spills. Many manufacturers recommend replacing a forklift's hydraulic oil every 1,000 hours of use.


Consult the forklift operator's manual, if available. It will tell you the specific grade of hydraulic fluid to use as well as what the particular fill level of the hydraulic tank is. If the manufacturer's recommendation cannot be found, use a general purpose fluid like ISO 32 hydraulic oil.


Park the forklift on level ground. Lower the forks until they touch the ground, set the parking brake, and turn the ignition off.


Locate the hydraulic reservoir. It will have a vented fill cap on its top side and a sight glass or fill gauge on its side to indicate the fluid level.


Remove the vented fill cap. Insert the oil delivery pump's discharge nozzle into the fill tube and begin pumping fluid into the reservoir.


Observe the tank's fluid level by via the sight glass or fill gauge. Once the fluid level reaches the max fill line, stop pumping. Do not overfill the tank.


Slowly withdraw the delivery pump's fill nozzle. Use a shop towel to contain or clean up any hydraulic fluid that may have spilled onto the outside of the tank.


Finish filling the forklift's hydraulic tank by replacing the vented fill cap.


  • Never exceed the manufacturer's prescribed fill level. Thermal expansion will cause hydraulic fluid to pour out of the hydraulic tank and cause a spill.

Items you will need

About the Author

Matt Kester began writing professionally in 2011. His ten years of experience in the construction, transportation and oil and gas industries give him a broad technical knowledge base to draw upon for writing eHow articles. Currently a student, Kester will receive his B.A. in political science from Arizona State University in May, 2012.

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