Turn off the washing machine and remove any detergent or fabric softener dispensers according to the manufacturer's instructions.
Rinse the dispensers under hot running water and scrub them with an old toothbrush to remove any buildup. Put the dispensers back into place on the washing machine.
Pour 1/2 gallon of white or cider vinegar into the washing machine.
Set the washing machine to a full hot water cycle. Allow it to run through the cycle completely.