Bosch dishwasher picks its moment

Check the drain hose hasn't got kinked or squashed flat.

Sounds like drain pump seized or jammed. Probably very simple to fix. The rotor and impeller are usually sealed inside a waterproof case, and it relies on the water to lubricate it. It can get fine food in the bearings. Dissassembly and washing out fixes that. Alternatively, it might be something too big (usually long and thin) has got through the filter and is jamming the impeller.

You should be able to empty the water out manually by laying the drain hose flat onto the floor, and into a shallow container.

Bare in mind that any machine you buy today will not have been designed with the longevity of your 18 year old machine.

Thanks, I've tried that, let's see what happens.

"Vague humming noise" sounds like a stuck pump.

There may be a little cover you can remove under the filters that lets you get to the impeller blades - probably needs a torx bit. HAve you and is the impeller free to rotate (sometimes a bone or hard crud gets stuck there).

I would feel no shame in replacing it.

That would be nice but I don't see anything like that.

I've drained it as advised by Andrew Gabriel (thanks, worked perfectly) and what I'm left with is this:

... which looks like an unassailable bit of plastic.

Quite so. We *must* have a working dishwasher by New Years Eve, I have little time between now and then, and it's likely to be a lot easier to get a new one delivered than to get this one repaired at this time of year. If I could easily get to the pump and free it as you suggest that would be good, but I think it's not possible with this particular model.

The drain pump is probably accessed from the bottom or perhaps from the side. It is likely to be the same as a washing machine one, i.e. a small squirrel cage motor attached to a conventional plastic centrifugal pump. Later dishwashers tend to have built in "leak containment" which makes access more difficult, but with old ones just tip it on its side and you may be able to get at the pump relatively easily.

Yes. The drain hose will almost certainly be attached directly to the drain pump's outlet. Detaching the hose may just get you enough access to the impeller to see if it turns, and possibly even to see if something is jammed in it. Otherwise, you will probably have to open the impeller case for better access.

If you pull the drain hose off, they can be stiff to get back on (although probably not after 18 years). If so, lubricate the rubber surface with some liquid soap so it slips on easily.

So I tipped it on its side and the drain hose is attached to an elbow, so I had to remove the elbow (two torx screws, one nigh-on inaccessible). I can't see in but I poked a screwdriver down there and felt that the impeller moved freely.

On mine that bottom bit would come out exposing some of the impeller.

But maybe mine was a design improvement made over the years and yours is a 1 piece casting?

Remove the filters and then remove the cover for teh pump (one screw, or some are levered up with the end of a spoon, see manual).

The impeller is then accessible; perhaps something is jammed in it.

If you gop for a new one I can recommend both AO

and Co-Op electrical

Good service from both, with quick, named day delivery on lots of the stock.

Can second that, got next day delivery, on a Sunday, in May, for a Bosch dishwasher.

Bought a freezer, a fridge and a dishwasher off them in the last 3 months (separately). All were delivered on time, helpful delivery people, good price.