An improved method of upgrading an image transfer engine such as, for example, an ink jet fluid printer or plotter using liquid ink, or a xerographic device using a liquid toner is disclosed. A removable ink flush tank/cartridge containing an ink cleaner is substituted for a removable ink tank, permitting complete cleaning of ink from the ink fluid flow paths in the engine. This results in less contamination of new inks with previously used inks in the engine.