Dishwasher Making Loud Noise? Here's Why

Dishwashers make noise during normal operation --- the hum of the pump, water spraying, and the occasional clunk of dishes shifting. But grinding, banging, squealing, or rattling that's new or getting worse is your dishwasher signaling a problem. Here's how to identify what you're hearing.

Grinding Sounds

Foreign Object in the Drain Pump

A grinding noise during the drain cycle --- often rhythmic and mechanical --- almost always means something is caught in the drain pump impeller. Glass shards, small bones, toothpicks, and fruit pits are common culprits. Continue using the machine with something caught in the pump and you'll damage the impeller, requiring a full pump replacement.

Fix: clean the filter and inspect the pump area underneath the filter assembly. Remove any foreign objects with needle-nose pliers. Always check dishes for small items before loading.

Worn Wash Pump Bearing

A low grinding or rumbling during the wash cycle (not drain) can indicate a worn bearing in the wash pump motor. This is a progressive failure --- the noise will get worse over time. Wash pump replacement is a technician repair.

Banging or Thumping

Dishes Shifting During Spray

Lightweight items on the top rack --- plastic cups, lids, lightweight containers --- can be knocked around by the force of the spray arms. This causes a rhythmic banging that tracks with the spray arm rotation speed. Secure lightweight items by facing them downward and wedging them between tines.

Spray Arm Hitting Dishes

If a spray arm is hitting a tall item or something that's shifted position, it makes a repetitive thumping that's easy to diagnose --- open the dishwasher and manually spin the spray arms to see if anything is in their path. Reload as needed.

Rattling

Rattling during the cycle is almost always caused by loose items in the dishwasher --- a utensil that's fallen through the rack, a small lid that's vibrating against the tub, or a rack with a broken tine that's allowing items to shift. Check the dishwasher interior and secure or remove any loose items.

Loud Humming

A louder-than-normal humming during the wash or drain cycle can indicate a pump that's working harder than it should --- often because of a partial blockage or a bearing that's beginning to fail. Clean the filter and drain area first. If the humming persists after cleaning, have the pump inspected.

Squealing or High-Pitched Noise

A squealing sound during the cycle typically comes from a worn bearing in the wash pump motor or the circulation pump. This is a component that's deteriorating --- the sound will worsen over time, and eventually the pump will fail. Schedule a service call sooner rather than later; catching it before full failure is less expensive.

Knocking at the Start of a Cycle

A knock or bang at the very start of the fill cycle is usually water hammer --- a pressure surge in your home's pipes when the inlet valve opens rapidly. This isn't a dishwasher problem --- it's a plumbing issue. Installing a water hammer arrestor on the supply line near the dishwasher resolves it.