Do system cleaners work?, no they don't. You can use any on the market like DU Cleaner, clean your phone using that which I just used and it found 761mb of junk which I deleted, then I used Super Speed Clean which found 847mb of junk so no, they don't work. The only way to delete junk is to go into recovery and delete cache and dalvik cache so save your money people and forget about these apps.