Siemens dishwasher squeals loudly but works fine otherwise

[qazwsxedc]

My Siemens dishwasher, about nine years old, makes a really loud squealing noise for 10-20 minutes at a time while it's in the middle of its programme. Think banshee with a stubbed toe, about 2kHz, and loud enough to be heard throughout the house.

It doesn't do that when filling or emptying, only right in the middle of its programmes. It washes and dries the dishes just fine, and there are no error codes.

I've heard bearing failures in electric motors of other appliances before, and they weren't as loud, nor was the sound as steady as this one. Could this be a bearing failure of the main pump motor anyway, or is there something else to look at first?

 

[dishman]

Middle of it's programmes? How many times per wash? What specifically is it doing at those times? Heat cycle?

Have you tried pulling it out- taking the sides off and seeing if it makes it easier to audibly locate the noise.

 

[qazwsxedc]

The noise happens once per wash cycle. It starts roughly 20 minutes into a wash cycle, plus or minus ten minutes, I'd say. It persists for ten to 20 minutes, then stops again while the wash cycle continues. The noise does not occur when the dishwasher is filling or draining. The water is already hot when the noise starts, and it is still hot when it stops. Noise is loudest at the bottom right. (Fill and drain hoses aren't long enough to operate the dishwasher while it is pulled out of its surroundings, which is why I haven't tried that.) Gently pushing the door while it is noisy doesn't change the noise, so I'm reasonably confident it isn't a door gasket whistling.

In short, the noise does occur when the main pump is active, but only for part of the time it is running, and it doesn't correlate to water temperature. If this was a problem with worn motor bearings I would have thought they'd be noisy all the time. I'm trying to avoid ordering a £200 spare part only to find that it doesn't fix the problem. What else is active at these times, and receives enough energy input to make such a racket? Or is there something in what I described which clearly points at the pump?

 

[dishman]

It could be just a sign of bearing wear. While not directly related to the heat, it could be that the temperature change causes said parts to squeal at a certain point due to expansion and contraction.

I have an old tumble dryer for example, and it lets out a sequel like an old car when it starts up cold, but once it has heated up, it is fine. I cannot complain as it is 30+ years old...

A sequel would suggest something bearing related. The drain pump is not that hard to check on the siemens. Maybe check if there is some sort of crap caught in it which is impairing it's function. Check all the impeller blades are all intact.

I would still suggest removing the sides, and physically look at the areas of concern. The motor is very visible when the sides are off so it should make it easier to exclude.

 

[qazwsxedc]

Thanks dishman for your replies. For the benefit of anyone who ends up googling this, the noise did come from the main pump after all, but the fix didn't require replacing it. Instead, vinegar in a bowl plus a liberal application of baking soda in an otherwise empty dishwasher, run through the hottest cycle, plus two more hottest cycles run with only detergent did the job.
My pet theory is that there was buildup of something organic (shudder) in the innards of the dishwasher because it normally only was run on the low temperature "eco" cycle, and a couple of high temperature cycles plus the bubbling action from the vinegar/baking soda combination dislodged that. Similar to running a service wash in a washing mashine.