A method for remanufacturing toner cartridges, wherein original equipment manufacturer (OEM) sealant is removed and replaced with an aftermarket sealant. A hopper assembly is disassembled from a toner cartridge and cleaned to remove residual toner. The hopper assembly is then heated using an oven, heat gun, etc. in order to loosen the OEM sealant binding the hopper assembly. Once thoroughly heated, the hopper assembly is dismantled into a hopper section and a mag section. The OEM sealant is removed from the hopper section and replaced with the aftermarket sealant using an automated robot as the hopper section is held by a jig. A floating mag gasket attached to the mag section is either cleaned and reinstalled or replaced with a new floating mag gasket. The mag section is then reattached to the hopper section using an alignment tool in order to ensure proper positioning of components to create a fluid tight seal.