There are a variety of reasons as to why your toner cartridge is leaking. Unless you are ready to replace it, make sure that you do not remove any affected parts of your machine as this could lead to worse damages. The cause of leakage with your toner cartridge can be determined in a few ways. Shaking Works Like Magic (Not!) If you’re someone that doesn’t have a replacement ready at home for your toner, you might be one of the people that have tried the old shaking method.