Forklift engines are usually powered by propane tanks, but their lifting ability comes from hydraulic systems. Forklifts use a combination of hydraulic lift cylinders and a chain and pulley system to raise, lower and manipulate heavy loads. The lift cylinders on forklifts are typical hydraulic cylinders. Once removed from the forklift, they can be disassembled and rebuilt and reinstalled like most other hydraulic cylinders. You can purchase a cylinder seal kit containing every seal that should be replaced to rebuild the lift cylinder.
Disassemble the Cylinder
Bring the lift cylinder to a clean work space and remove any hydraulic caps and plugs from the cylinder's fluid ports.
Empty the lift cylinder hydraulic fluid into a bucket or other container.
Clamp the lift cylinder in a bench vise.
Unscrew the gland nut from the rod end of the lift cylinder. Some cylinders may have an additional retaining device, such as a snap ring that will have to be removed first.
Pull the piston rod out of the cylinder and clamp it in a soft-jawed vise.
Remove the nut or bolt holding the piston to the piston rod if the rod and piston are separate parts.
Pull the piston and gland off of the piston rod.
Reseal the Cylinder
Remove the seals from the piston and the gland with a seal pick.
Clean all the lift cylinder parts with a safe, petroleum-based solvent, then air dry the parts.
Install new seals from the lift cylinder seal kit onto all the cylinder parts.
Reassemble the Cylinder
Slide the gland back onto the piston rod, and then attach the piston. Reinstall the nut or bolt that holds the piston.
Slide the piston rod assembly back into the lift cylinder barrel.
Tighten the gland nut or reinstall the snap ring or other retaining device at the rod end of the cylinder.