The short answer
The WAT family puts a heavy counterweight at the top of the cabinet and suspends the tub on springs and dampers below it. That construction is why levelling matters so much on these machines and why a knocking noise so often turns out to be a damper rather than a bearing.
The observable tells
- The machine walks across the floor on spin — Feet, floor or load. The noise is a symptom of the movement, and stopping the movement stops the noise.
- Loud only on one programme — Different programmes use different spin speeds, so this normally means the noise has a speed threshold rather than a cause of its own.
- A humming machine that does not turn at all — The motor is being asked to move a drum that will not move, and that is a jammed-drum fault rather than a noise fault.
- A metallic rattle at low drum speed — Something loose is riding in the drum or has passed the seal into the sump. It is audible at slow speeds because nothing is masking it.
- A squeal on the first rotation of every wash — Usually the door seal or a belt taking up its slack rather than anything structural.
Ranked causes for these models
- Drain pump impeller fouled — Produces a harsh noise on drain only, which is why the timing of the noise within the cycle matters so much on this diagnosis.
- Transit bolts still fitted or partly backed off — Only on a machine that has been moved, but on such a machine it is the very first thing to check and the noise is unmistakable.
- Foreign object in the sump or between drum and tub — Coins, wires and clips pass the seal and grind continuously. It ranks high here because it is common and because it does real damage if left.
- Unbalanced or under-loaded drum — First on this family by frequency: a small heavy item alone in a large drum cannot be balanced, so the machine either bangs or refuses to reach speed.
What to check first, second, third
- Run a spin with the drum empty — It removes the load variable entirely, which is the single biggest source of noise on this family, and it costs one short cycle.
- Press and release each cabinet panel while the noise runs — A rattle that changes under your hand is panel resonance and needs no part at all.
- Rock the cabinet at each corner — Any movement means a foot is not carrying weight, and everything downstream of that is unreliable until it is fixed.
- Listen for whether the noise tracks drum speed — Speed-tracking noise is mechanical and in the rotating assembly; constant noise is not, and that split is the most useful one you can make.
Before you open anything
Safety
Kill the power first. If the machine needs to come forward, walk it rather than dragging it: these cabinets carry a heavy counterweight at the top and they tip more easily than their weight suggests.
Models in the WAT family
Reference| Model number | Family key |
|---|---|
| WAT28400UC | bosch:washer:wat |
| WAT28401UC | bosch:washer:wat |
| WAT28402UC | bosch:washer:wat |
When to stop and book a visit
Book a visit when the same fault returns after a correct repair. A repeat failure on these machines usually means a second fault upstream, and chasing it from the outside costs more weekends than it saves.
Nearest pages of this class
Lead Appliance Repair Technician · 12 years experience
Experienced technician with 12 years specializing in washing machine and dryer repairs across all major brands.
