ATP AT-212 Re-Seal Aerosol Can
Re-Seal is a special plasticizer which softens and expands hydraulic seals to stop leaks.  It will work on any hydraulic system (except brake) including jacks, lifts, plows, and industrial equipment. It works quickly (engine main seals will require 5 hours of running time) and will not cause the seal to become gummy or break down like other products.