What a new noise usually means on a Bosch
On a Bosch dishwasher a new noise is usually something loose in the water path rather than a failing pump. Because these machines have no food grinder and a very low noise floor, a glass chip, a fruit pit or a fallen item lands in the sump and is heard on the first cycle. Levelling and cabinet fixings account for most of the rest. Finding the item is owner work; reaching the pump is not.
What you are seeing and hearing
- A rattle or click that comes and goes with the wash arm passing a point.
- A grinding or grating noise that rises with pump speed.
- A rhythmic knock felt through the counter more than heard.
- Noise only during the drain part of the cycle.
- Not this fault: A one-off bang at fill, felt in the pipework - that is water hammer in the plumbing.
- Not this fault: A hum with no wash action at all - read the will-not-start page instead.
Most likely causes, in Bosch order
- Foreign object in the sump or against the filter — Why ranked: First on Bosch specifically. A quiet machine with no grinder makes a single chip or pit audible on the cycle it arrives.
- Debris in the drain pump impeller — Why ranked: Ranked second because the timing gives it away: silence through wash, rattle the instant the drain pump runs.
- Machine not level, or cabinet fixings loose — Why ranked: Bosch machines carry their weight through side or counter fixings. A loose fixing turns normal pump vibration into cabinet resonance.
- Loading - cutlery or a light item contacting a spray arm — Why ranked: Intermittent by nature, and it moves when you reload. It explains a noise that appears on some cycles only.
- Circulation pump bearing wearing — Why ranked: Last by frequency. It builds over months as a constant tone that rises, rather than the intermittent noises above.
What to check, in order
- Note exactly when in the cycle the noise happens - fill, wash or drain. — Because: That single observation separates rank one and four from rank two, before anything is opened.
- Remove the filter assembly and look and feel through the sump. — Because: Rank one is usually visible, and it is the cheapest possible outcome.
- Reload the racks and rerun; check that nothing touches a spray arm. — Because: It confirms or clears rank four without tools.
- Press on the counter above the machine while it runs and check the fixings. — Because: If the noise changes under hand pressure, it is rank three and not a pump at all.
Checks you can do safely
- Run a cycle and write down when the noise starts and whether it follows the sweep of the spray arm. — N: 1 — Tools: Notepad — Time: one cycle
- Twist out the filter cylinder, lift the coarse filter, and sweep the sump gently with a gloved hand and a torch. — N: 2 — Tools: Torch, gloves — Time: quick
- Spin each spray arm by hand with the racks loaded and look for contact points, then reload anything that touches. — N: 3 — Tools: None — Time: quick
- Check the fixing screws that hold the machine to the counter or cabinet sides and confirm the feet sit firmly on the floor. — N: 4 — Tools: Screwdriver — Time: moderate
- Stop rule: Stop here. Removing the sump cover or the pump to clear the drain impeller is service work on a machine that is usually hard-wired.
Before you open anything
Safety
Switch off the dishwasher breaker before removing the toe kick or any panel. A capacitor can hold a charge after the power is off. Never sweep a sump with bare fingers. Assume broken glass in any dishwasher making a grinding noise; wear gloves. Stop running a machine that grinds - it pulls debris further into the pump.
When this becomes a service call
The noise persists with a clear sump, correct loading and tight fixings. Grinding continues, which means debris is already past the filter. A constant tone has risen over months, pointing at a pump bearing. The machine leaks as well as makes noise, which changes the priority entirely.
Nearest pages
What this page does not cover
This is generalized information for Bosch dishwashers as a group. It does not separate the quieter upper series from the entry series, whose baseline noise differs, and it names no model-specific parts. Where a family- or model-specific page exists it supersedes this one; no narrower page sits beneath this scope yet.
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
