Dishwashers require very little maintenance until something begins going wrong and needs repair or replacement. If your dishwasher begins making a loud, buzzing noise, it could be because something is stuck in the pump intake, things in the dishwasher are rubbing up against one another or if the dishwasher is new or hasn't been run in a long time. Under certain circumstances, a loud buzzing noise might be normal.
Blocked Pump Intake
A dishwasher's pump intake collects large food chunks and other pieces of debris. Under normal circumstances, it does not make any noise. However, if a glass breaks and a piece becomes lodged in the pump intake, it could cause a loud grinding and buzzing noise. This also occurs if a small piece of hard plastic gathers there. Fix this by opening the pump intake and cleaning it out.
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Dry Pump Seals
New dishwashers or dishwashers that haven't been used in a while have dry pump seals. Under normal and consistent use, pump seals become lubricated with water and do not make any noise during the washing process. Dry pump seals make a buzzing noise. Pouring 1 quart water into the dishwasher's bottom removes these sounds.
Improperly loading your dishwasher causes the dishes to rattle against one another during the cycle. Sometimes, a light plastic cup or container causes a buzzing noise if placed against another object in the dishwasher. Determine if this is the cause by running the dishwasher when it is empty. If the noise continues, something else is responsible.
Normal Wear and Tear
Unless your dishwasher is specifically designed to be silent, or near silent, the dishwasher normally makes a buzzing or humming noise. These sounds some from the fan that cools the motor, the soft-food disposer and the drain pump, and are a sign that the machine is operating correctly. New dishwasher shouldn't be very loud but in time the fan, food disposer and drain pump begin wearing out and get louder. Replace these components or purchase a new dishwasher.