Dishwasher Making Grinding or Chopping Noise

Common Symptoms

• Loud grinding, crunching, or chopping sound during the wash cycle
• Rhythmic clicking or rattling that occurs during the drain cycle
• Grinding noise that appears suddenly after loading dishes with bones or glass
• Spray arm making a repetitive ticking sound as it rotates
• Noisy cycle accompanied by reduced cleaning performance
• Grinding that stops when you pause the cycle and restart it

Most Likely Causes

1. 1

   Broken Glass or Hard Debris in the Chopper Blade (Most Common)

   Many dishwashers — particularly Whirlpool and Maytag models — have a food disposer or chopper blade at the bottom of the tub that grinds food particles small enough to pass through the drain. A chip of broken glass, a bone shard, a fruit pit, or a hard plastic fragment that falls off a dish can lodge in or around the chopper blade, causing a loud grinding or chopping noise. The noise typically occurs throughout the entire wash cycle. SAFETY: Always unplug the dishwasher and wear cut-resistant gloves before reaching into the chopper area — broken glass is a serious hazard.

2. 2

   Spray Arm Cracked or Hitting a Rack or Dish

   A cracked spray arm can produce a grinding or knocking noise as it rotates and the cracked section catches on the bottom of the rack or on tall items. Similarly, an improperly loaded dish that hangs below the rack edge can be hit by the rotating spray arm repeatedly — this produces a rhythmic ticking or knocking sound that is worst at one point in the spray arm's rotation. The noise stops when the offending item is removed or the rack is reloaded correctly.

3. 3

   Pump Impeller Wear or Damage

   The circulation pump's impeller (a small fan-like component that propels water through the spray arms) can develop cracks, chips, or wear after years of use. A damaged impeller produces a grinding or humming noise during the wash cycle. Unlike debris-related grinding (which often varies in pitch), a worn impeller produces a consistent grinding hum. Impeller damage is often caused by hard debris that entered the pump — after removing the debris, check whether the impeller itself was damaged.

4. 4

   Hard Food Debris in the Drain Pump

   The drain pump, which expels used wash water at the end of the cycle, can grind if hard food debris (olive pits, fruit seeds, bottle caps, small bones) enters the pump housing. Drain pump grinding occurs specifically during the drain phase — typically in the last 2–3 minutes of the cycle and at the start of the cycle if residual water drains first. The noise may be accompanied by slow or incomplete draining.

5. 5

   Wash Motor Bearing Failure

   The wash motor's internal bearings can wear out over time, particularly on machines over 8–10 years old. A bearing failure produces a consistent grinding or humming noise throughout the entire wash cycle — not just during drain. The noise typically worsens over time and is not affected by removing debris. Motor bearing replacement requires removing the pump and motor assembly and is an advanced DIY or professional repair. On older machines, motor failure may trigger the consider-replacing threshold.

Quick DIY Checks

1. 1**SAFETY FIRST — UNPLUG BEFORE INSPECTION**: Before reaching into the dishwasher tub area or filter area, unplug the dishwasher from the wall outlet or turn off its dedicated circuit breaker. The wash motor and drain pump can start unexpectedly if the dishwasher is plugged in. Wear cut-resistant gloves when handling the filter and chopper area — broken glass fragments are frequently present when the grinding noise complaint is filed.
2. 2IDENTIFY WHEN THE NOISE OCCURS — WASH CYCLE vs DRAIN CYCLE: This diagnostic step is critical. Listen carefully to when the grinding sound occurs: - **During the main wash cycle** (first 20–40 minutes): Points to the spray arms, chopper blade, or circulation pump impeller. - **During the drain phase** (last 2–5 minutes, water being expelled): Points to hard debris in the drain pump. - **Both phases**: Multiple debris sources or pump damage. - **Rhythmic clicking at one point per rotation**: A spray arm is hitting a rack or dish. This distinction guides which component to inspect first.
3. 3REMOVE AND INSPECT THE FILTER AND CHOPPER AREA: Pull out both rack tiers and set them aside. Remove the filter assembly from the bottom of the tub (usually a twist-lock cylinder — counter-clockwise to unlock). Beneath or adjacent to the filter, locate the chopper blade area (on Whirlpool/Maytag food disposer models, this is a recessed area with a blade guard). Use a flashlight to look for broken glass, bone chips, plastic fragments, or hard debris. Using tongs or gloved fingers, carefully remove any foreign material. Check the chopper blade itself — it should spin freely when pushed; a blade that is stuck or grinds when turned by hand indicates trapped debris or damage. **Whirlpool food disposer models**: The food disposer grinder is located below the filter area; access requires removing the filter cylinder and the disposer screen beneath it. Clear debris from both the grinder and the screen.

1. 4INSPECT AND TEST THE SPRAY ARMS: Remove both spray arms (lower arm typically unscrews counter-clockwise or pulls straight up; upper arm unscrews similarly). Examine each arm closely for cracks, chips, or broken sections — a cracked arm can catch on racks during rotation. Also check that the center hub bearing (where the arm mounts) is intact and the arm rotates smoothly without binding. Reinstall the arms without racks present and manually spin them to confirm they complete a full rotation without catching. Reload dishes and rack height per the loading guide, ensuring no items extend below the rack floor. **Bosch EcoSilence motor note**: Bosch dishwashers with EcoSilence motors are specifically engineered to run nearly silently — any grinding from a Bosch is abnormal and almost always debris-related rather than normal motor noise. The Bosch spray arm snaps onto a central hub; confirm it is fully locked before running a cycle.
2. 5CLEAN THE PUMP FILTER AREA AND CHECK FOR IMPELLER DAMAGE: After removing debris from the chopper area and filter, inspect the pump inlet area (visible below the filter housing with a flashlight). Look for small shards or particles embedded near the pump inlet screen. On accessible models, gently poke the pump inlet screen with a toothpick to dislodge any small glass slivers. Reinstall the filter, reload dishes, and run a short cycle. If grinding continues, the impeller may be damaged — the impeller is accessible on some models by removing the pump housing cover (requires full tub disassembly and is a 2–3 hour intermediate repair).
3. 6ACCESS THE DRAIN PUMP IF NOISE OCCURS DURING DRAIN PHASE: If grinding is isolated to the drain phase, the drain pump requires inspection. On most dishwashers, the drain pump is accessed from underneath: (1) Unplug and disconnect the water supply and drain hose. (2) Carefully tip the dishwasher onto its back (place cardboard down to protect the floor and the machine's finish). (3) Locate the drain pump — a small round or rectangular pump motor near the bottom of the tub. (4) Inspect the drain pump inlet for hard objects (olive pits, seed pods, plastic fragments). (5) If accessible, turn the pump impeller by hand — it should spin freely; grinding when rotated by hand indicates debris or impeller damage. **Miele**: Miele dishwashers have a dedicated pump filter access flap at the bottom-front interior of the tub — remove this flap to access the pump filter directly without removing the machine from the cabinet. Clean the Miele pump filter with a brush under running water.
4. 7TEST AFTER REPAIRS: After removing debris, cleaning the filter, and inspecting the spray arms, plug in the dishwasher and run a short wash cycle (Quick Wash or Rinse-only). Stand next to the machine and listen throughout the cycle — during fill, wash, and drain phases. If the grinding is gone, the repair is complete. If a faint grinding remains only during drain, run 2–3 more cycles — small residual particles often flush out on their own. If loud grinding persists unchanged after full debris removal and spray arm inspection, the pump impeller or motor bearing is damaged and the pump assembly will need professional inspection or replacement.

Repair vs Replace

Recommended Tools & Parts

• Dishwasher Filter Assembly (Replacement)

  If the filter housing is cracked or damaged by debris, replace the complete filter assembly. Use your full model number to find the correct part.

  $15–$45

  Buy on Amazon →

• Dishwasher Spray Arm (Lower or Upper)

  Replacement spray arm if the original is cracked, broken, or has a damaged hub bearing. Available as lower, upper, or middle (three-rack) arm. Model-specific.

  $15–$45 per arm

  Buy on Amazon →

• Dishwasher Drain Pump

  Replacement drain pump motor if debris has damaged the impeller. Most drain pumps are a complete replacement unit. Model-specific — confirm with your full model number.

  $40–$120

  Buy on Amazon →

• Dishwasher Circulation Pump Assembly

  The main wash pump that drives water to the spray arms. Replacement is needed if the impeller or motor bearing is damaged. Advanced DIY or professional repair.

  $80–$200

  Buy on Amazon →

• Cut-Resistant Gloves

  Essential for safely handling debris in the chopper/filter area when broken glass is suspected. Use before every inspection of the tub bottom and filter area.

  $10–$20

  Buy on Amazon →

Links are Amazon affiliate links (tag: fixitfastai-20). Prices are estimates.

Related Repairs