Why do hydraulic cylinders leak?

Hydraulic drift is the leading cause of leaks in the hydraulic cylinder. The drift happens when fluid moves from one side of the piston to another, creating an imbalance. The imbalance causes the cylinder to drift towards retract position while unable to hold at the mid-stroke position. This causes the cylinder to become hydraulically locked, which means the cylinder can only move if fluid escapes via the piston seal or a worn cylinder barrel.