Thermador dishwashers are built to run quietly, so a new grind, hum, or knock stands out. Some of those sounds are normal, and only a few point to a real fault — here’s how to tell them apart.
An alarming noise? Call 844-975-6696 or book a visit.
Quick guide
| The sound | Likely cause | Normal? |
|---|---|---|
| Soft swish of water | Spray and fill | Yes — normal |
| Low whir during drain | Drain pump | Yes — normal |
| Knocking or thumping | Spray arm hitting a tall item | No — reload |
| Grinding | Object in the pump | No — check the sump |
| Squeal or loud hum | Worn pump bearing | No — needs service |
The normal sounds first
A soft swish of water spraying, a gentle hum during the wash, and a low whir when it drains are all normal. Because these machines are so quiet to begin with, those everyday sounds can seem louder than they are. What isn’t normal is grinding, knocking, squealing, or a loud buzz.
The sounds that mean a problem
- Knocking or thumping. Usually a spray arm hitting a tall pot or utensil — a loading fix.
- Grinding. A foreign object — glass, a seed, a chip — caught in the pump or sump.
- Squeal or loud hum. A worn wash or drain pump bearing, which gets worse over time.
- Rattling. A loose item in a rack or something vibrating against the tub.
If the noise is the drain pump and the dishwasher also isn’t emptying, see why it isn’t draining — the two often go together.
Step-by-step: locate the noise
- Note when it happens. During the wash or only when draining — each points to a different pump.
- Reload for clearance. Make sure nothing tall blocks the spray arms from spinning.
- Check the sump. Remove the filter and look for glass or debris caught below.
- Spin the spray arms. Confirm they turn freely without catching.
- Listen for a squeal. A rising squeal or loud hum points to a pump bearing, not loading.
When to call a technician
Book a visit soon for grinding that isn’t a removable object, or a squeal or loud hum from the pump. The wash and drain pumps are tested for continuity and bearing wear before replacement — running a grinding pump can damage the impeller and turn a small fix into a bigger one. Book Thermador dishwasher repair before it worsens.
It can wait if reloading or removing a stray object silenced it — that’s not a fault.
What the repair actually involves
A technician traces the noise to the wash or drain pump, clears any object from the sump, then tests the pump for continuity and a worn bearing. A failed pump or motor is replaced — a defined part in the least-expensive to mid category — or a spray arm if that’s what was catching. The main cost driver is a simple object removal versus a pump. You get a written estimate before any work, and common pump parts are stocked for a single visit.
Is it safe to use until then?
Normal swishing and humming are completely safe. A grinding noise is the one to stop on — pause the cycle and check the sump for an object, because running it can damage the pump. A worn-bearing squeal is safe short-term but best serviced before the pump fails.
Preventing it
- Scrape plates so seeds, pits, and glass chips don’t reach the pump.
- Load so nothing overhangs or blocks the spray arms.
- Clean the filter regularly to keep debris out of the sump.
Frequently asked questions
Q: Why is my dishwasher making a grinding noise?
A: Usually a foreign object — glass, a seed, or a chip — caught in the pump or sump. Pause the cycle, remove the filter, and check for debris. If it grinds with nothing there, the pump needs servicing.
Q: Why does my dishwasher knock or thump during a cycle?
A: Almost always a spray arm hitting a tall pot, pan handle, or utensil as it spins. Rearrange the load so nothing overhangs the arms and the knocking stops.
Q: How quiet should a Thermador dishwasher be?
A: Very — they’re among the quietest dishwashers, often barely audible beyond a soft water swish. That’s exactly why a new grind, squeal, or hum is worth investigating; it’s a real change from how the machine normally runs.
Q: Is a humming noise from my dishwasher normal?
A: A soft hum during the wash is normal. A loud hum or buzz that’s new points to a pump working hard or a bearing starting to fail, and it’s worth checking before the pump gives out.
Quiet it down
If a pump or bearing is behind the noise, we’ll test it and replace it. We handle Thermador dishwasher repair with a written estimate before any work starts.
Call 844-975-6696 or book online. Same-day service is usually available in New York, Los Angeles, Chicago, San Francisco, Houston, and Miami.