The short answer
Most new noises from a Blomberg dishwasher come from the tub rather than from a bearing: a spray arm striking an item, cutlery vibrating in the basket, or debris in the drain-pump chamber. These are quiet machines, which is why owners notice a change quickly, and the loading causes are far more common than mechanical failures. Run the machine empty once and most of the list below disappears, which is the cheapest diagnostic available on this appliance.
What you are seeing
- A regular tapping or knocking in time with the spray arm
- A rattle that comes and goes as the basket contents shift
- A grinding or crunching noise during the drain step only
- A humming that continues after the water stops moving
- A high whine that rises with the wash phase and falls at the end
- A near-miss symptom: a thump from the plumbing when the valve closes, which is water hammer in the house pipework
- Body: The rhythm of the noise identifies the source: A regular tapping or knocking in time with the spray arm. A rattle that comes and goes as the basket contents shift. A grinding or crunching noise during the drain step only. A humming that continues after the water stops moving. A high whine that rises with the wash phase and falls at the end. A near-miss symptom: a thump from the plumbing when the valve closes, which is water hammer in the house pipework.
Causes, most likely first
- A spray arm hitting the load — Why: a long knife, a tall jug or a handle hanging below the upper basket catches the arm once per revolution, giving a regular tap that stops when the load is rearranged.
- Debris in the drain-pump chamber — Why: glass, stones and pips reach the impeller and grind only during the drain step, which is the timing clue.
- Items rattling against each other — Why: lightweight bowls and stainless items resonate under the spray, and this is the noise most often mistaken for a failing bearing.
- The machine touching the cabinet or a worktop — Why: a compact machine that was pushed in without its anti-vibration ties transmits normal pump vibration into the whole cabinet run.
- A worn circulation-pump bearing — Why: a continuous whine present through the whole wash phase and unchanged by loading, which is what separates it from everything above.
- A failing drain pump — Why: a hum that continues without water moving, and it usually arrives with a drainage complaint rather than alone.
- Body: Ranked by how often each one turns up on an inspection: First, A spray arm hitting the load: a long knife, a tall jug or a handle hanging below the upper basket catches the arm once per revolution, giving a regular tap that stops when the load is rearranged. Second, Debris in the drain-pump chamber: glass, stones and pips reach the impeller and grind only during the drain step, which is the timing clue. Third, Items rattling against each other: lightweight bowls and stainless items resonate under the spray, and this is the noise most often mistaken for a failing bearing. Fourth, The machine touching the cabinet or a worktop: a compact machine that was pushed in without its anti-vibration ties transmits normal pump vibration into the whole cabinet run. Fifth, A worn circulation-pump bearing: a continuous whine present through the whole wash phase and unchanged by loading, which is what separates it from everything above. Sixth, A failing drain pump: a hum that continues without water moving, and it usually arrives with a drainage complaint rather than alone.
What to check, in order
- note whether it happens during the wash, the drain, or both, since that alone splits the causes in half.
- run the machine empty: a noise that disappears with an empty tub was a loading problem.
- if the noise is only on the drain, look for debris in the pump chamber under the filter.
- a whine present on an empty machine and unchanged by loading is mechanical, and that is where owner checks stop.
- Body: Use the timing of the noise, which is free information: First, note whether it happens during the wash, the drain, or both, since that alone splits the causes in half. Second, run the machine empty: a noise that disappears with an empty tub was a loading problem. Third, if the noise is only on the drain, look for debris in the pump chamber under the filter. Fourth, a whine present on an empty machine and unchanged by loading is mechanical, and that is where owner checks stop.
Checks you can do yourself
- Open the machine mid-cycle only after cancelling it, and check whether an item is standing in the arc of a spray arm — Tools: none — Time estimate: a few minutes
- Reload with tall items to the sides and nothing hanging below the upper basket, then rerun — Tools: none — Time estimate: an hour or more
- Unplug the machine, remove the filter stack and check the pump chamber for glass chips and stones — Tools: torch, gloves — Time estimate: a few minutes
- Spin each spray arm by hand and listen for grinding at the bearing, and check both are properly seated — Tools: none — Time estimate: a few minutes
- Run a full programme with the tub empty and note whether the noise remains — Tools: none — Time estimate: an hour or more
- Body: A short comparison run is more useful than any inspection: Open the machine mid-cycle only after cancelling it, and check whether an item is standing in the arc of a spray arm (none; a few minutes). Reload with tall items to the sides and nothing hanging below the upper basket, then rerun (none; an hour or more). Unplug the machine, remove the filter stack and check the pump chamber for glass chips and stones (torch, gloves; a few minutes). Spin each spray arm by hand and listen for grinding at the bearing, and check both are properly seated (none; a few minutes). Run a full programme with the tub empty and note whether the noise remains (none; an hour or more).
Safety first
Safety
Unplug the appliance or switch off its breaker before removing any panel. A capacitor can hold a charge after the power is off. Broken glass is the usual find in a pump chamber, so wear gloves and use a torch rather than feeling for it. Never reach into a tub while a cycle is running, and cancel the programme before opening the door on a hot machine. unplug-before-service
When to stop and call a technician
Mechanical noise needs a technician: The noise is unchanged with the tub empty and the filter clear. A grinding sound persists after the pump chamber has been cleared. The noise arrives together with poor drainage or a fault code. A metallic scraping that gets worse over successive cycles. The noise is unchanged with the tub empty and the filter clear A grinding sound persists after the pump chamber has been cleared The noise arrives together with poor drainage or a fault code A metallic scraping that gets worse over successive cycles
Nearest pages of the same kind
What this page does not cover
This page is generalized across every dishwasher sold under the Blomberg name: it separates neither the freestanding and semi-integrated stainless machines from the fully integrated panel-ready ones and the compact widths from the full-size cabinets, and it names no individual model. Where a family- or model-specific page exists it is linked here and it outranks this one for that machine; at present no page beneath this one narrows to a single family, so treat the ranking above as the brand-level pattern rather than a reading of your serial plate. For the other faults that turn up on this machine, start from Common Blomberg Dishwasher Problems.
Related pages
- Common Blomberg Dishwasher Problems
- Blomberg Dishwasher: Does Not Clean or Dry
- Blomberg Dishwasher: Controls, Display or Error Code
- Blomberg Dishwasher: Cycle Will Not Run or Complete
- Blomberg Dishwasher: Door, Latch or Seal Fault
- Blomberg Dishwasher: Will Not Drain
- Blomberg Dishwasher: Electrical, Fire or Gas Hazard
- Blomberg Dishwasher: Not Heating
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
