Quick Answer
A dishwasher that grinds, buzzes, squeals, or rattles during a cycle has mechanical wear or a foreign object obstruction in its pump or spray arm system. The most common sources are worn wash motor bearings (grinding or growling during the wash phase), a failing drain pump (buzzing during drain), a worn spray arm bearing (squeaking with each arm rotation), or a hard object lodged in the chopper blade assembly (sudden crunching). Identifying when in the cycle the noise occurs — wash phase vs. drain phase — is the most useful first diagnostic step.
Common Causes
Wash Motor Bearing Wear: The wash motor runs continuously during the wash and rinse phases, spinning the pump impeller and circulating water through the spray arms. Bearings inside the motor support the rotating shaft; as they wear from heat and age, metal-on-metal contact creates a grinding, growling, or squealing sound. The noise typically starts quietly and grows louder over weeks as the bearing continues to deteriorate. A seized bearing will stop the motor entirely mid-cycle.
Drain Pump Bearing Failure: The drain pump operates primarily during the drain phase to push water out through the drain hose. When the drain pump's bearings fail, its impeller wobbles inside the housing and strikes the pump casing, producing a loud buzzing or humming concentrated in the final minutes of the cycle. A cracked impeller causes a similar sound and may also produce a grinding quality.
Worn Spray Arm Bearing: The upper and lower spray arms rotate on bearings that allow them to spin freely as water pressure drives them around the tub. A worn spray arm bearing produces a rhythmic scraping or squeaking that corresponds to each rotation. The arm may also drop slightly, dragging against the rack or tub floor and intensifying the scraping sound.
Foreign Object in Chopper Assembly: Hard objects — bone fragments, fruit pits, broken glass, coins, small utensils — can pass through the filter and enter the chopper blade area near the pump. These objects strike the spinning blade with each pump rotation, producing sudden, loud crunching or rattling sounds. This type of noise typically starts abruptly rather than developing gradually.
Loose Mounting Hardware: Mounting brackets and leveling feet secure the dishwasher inside its cabinet opening. When these loosen from cycle vibration over time, the machine begins vibrating against the cabinet frame, producing rhythmic rattling or banging — especially pronounced during the drain phase when pump vibration peaks.
Checks You Can Do Yourself
Listen and time the noise: Note carefully when in the cycle the noise occurs. Wash-phase noise points toward the wash motor, circulation pump, or spray arm bearing. Drain-phase noise points toward the drain pump. Noise throughout the entire cycle may indicate loose mounting hardware. This single observation significantly narrows the component involved.
Run the dishwasher empty: Run a short cycle with no dishes loaded. If the noise is identical with an empty machine, the cause is mechanical — a worn component rather than a dish or utensil causing a one-time rattle.
Inspect the spray arms by hand: With the dishwasher off and cool, remove the lower rack and rotate each spray arm by hand. It should spin smoothly with minimal resistance. Stiff, jerky, or grinding rotation indicates a worn bearing. Look along the tub bottom for any debris — broken glass, bone fragments, small objects — that may have bypassed the filter.
Check machine levelness: Place a spirit level on the top edge of the open door. If the machine is not level, it will vibrate unevenly during the cycle. Adjust the front leveling feet to correct this — it rules out cabinet vibration as a cause before looking deeper.
What NOT to Do
Do not attempt to reach into the pump or chopper blade area to remove objects while the dishwasher is plugged in. The pump area contains sharp edges and electrical components. Always unplug before any internal inspection.
Do not attempt to disassemble the wash motor or drain pump housing. These are sealed units requiring specialized tools to open safely. Improper disassembly can allow water into electrical connections and create a shock hazard.
Do not continue running the dishwasher if the grinding is worsening or the machine is stopping mid-cycle. A motor bearing that is close to seizing can lock up suddenly, turning a routine bearing replacement into a full motor replacement.
When to Call a Professional
If the noise has persisted across multiple cycles, is getting louder week over week, or is accompanied by the machine stopping mid-cycle — the fault is in an internal component that requires disassembly to access. Confirming whether the wash motor, drain pump, or spray arm bearing is the source requires removing panels and testing components under power, which is not safe to perform without proper training on a water-connected appliance.
Sudden loud crunching warrants prompt attention: continued operation with a foreign object striking the chopper blade or impeller can crack those components, turning a simple cleaning into a pump replacement.
What a Technician Evaluates
A technician begins by running the dishwasher through a full cycle while listening carefully — characterizing the noise by type (grinding, buzzing, squealing, rattling), timing it to a specific cycle phase, and locating it within the machine (front, rear, bottom). The wash motor is inspected for bearing play in the shaft and abnormal vibration. The spray arms are tested for smooth rotation and bearing condition. The drain pump is checked for motor function and impeller integrity.
The filter and chopper blade assembly are removed and inspected for foreign objects, blade damage, and debris accumulation. Mounting brackets are checked for tightness. On machines with a separate circulation pump, that pump's bearing and impeller are evaluated independently. After identifying the failed component, the technician replaces it and runs a test cycle to confirm the noise has been eliminated before considering the repair complete.
Frequently Asked Questions
What sounds are normal for a dishwasher? Normal dishwasher sounds include a low hum or whir from the wash motor, the rush of water through spray arms, a single mechanical click when the detergent dispenser opens, and a louder pump sound during the drain phase lasting 20–30 seconds. These sounds are consistent cycle to cycle and do not worsen over time.
Can a foreign object in the chopper cause permanent damage? Yes. A hard object striking the chopper blade or impeller at speed can crack the blade, dent the pump housing, or chip impeller fins. Even after the object is removed, the damaged components may need replacement. Sudden crunching warrants prompt professional diagnosis rather than repeated cycle attempts.
How long can I safely use a dishwasher that's making a grinding noise? A mild squeak that is not worsening presents lower urgency — short-term use while arranging service is generally acceptable. A grinding or scraping sound that intensifies across successive cycles should be addressed promptly, as continued use accelerates bearing deterioration and risks component seizure.
Does noise mean the dishwasher needs to be replaced? Not usually. Wash motor replacements, drain pump replacements, and spray arm assembly replacements are standard repairs that restore full function. A technician can assess whether the machine is worth repairing based on its age, overall condition, and the scope of the fault — but noise alone is not a sign that replacement is necessary.
Related dishwasher issues? If the dishwasher is leaking along with making noise, see the dishwasher leaking guide. If dishes aren't getting clean, see the dishwasher not cleaning guide. For more troubleshooting information, visit the dishwasher repair resource page.
For professional repair service in Denver, see our dishwasher making noise repair in Denver page. Related: dishwasher not cleaning dishes in Denver.