Dishwasher performance deterioration after a year

[dogfonos]

Would appreciate any ideas/guidance on the following issue...

I started using a new Bosch Serie 4 dishwasher (SMS461W00G) in January 2019. It worked perfectly well for about the first year - I was impressed - but then performance started to drop-off such that, typically, tea mugs are frequently left stained after being washed (note, the tea stains remaining can be very easily removed afterwards by a single wipe with a dry cloth so were're not talking stubborn stains. And some mugs are new, some old yet it doesn't make a difference). I began using 1.5 dishwasher tablets which worked well for a few months but the tea mugs are, once again, coming out of the dishwasher with easy-to-remove stains.

Question is: why the performance drop-off? Is this normal? Any further performance deterioration and the machine won't be worth using.

Let's get the obvious things out the way:
Have always used the same wash program - one that doesn't use automatic debris detection, so the program is fixed/repeatable.
Have always used same, WHICH? recommended dishwasher tablets
Have set machine correctly for salt and rinse aid for the water hardness - and tablets used
Machine was levelled correctly during install and hasn't been moved since
Machine is never overloaded, items are always well placed/spaced
Nothing really dirty is put into machine
All filters are regularly cleaned (very little debris ever found on filters because I pre-clean items before loading into machine). The fine filter does tend to get a fine white coating of something and I remove that completely with a detergent scrub
All filters are in perfect condition
Never had any error codes. Machine appears to be working as it always has (although I suspect it isn't).

Tried an expensive Bosch-supplied sample tablet today and results were even worse. It's not just tea-stained mugs that are the problem, saucepans (rinsed clean beforehand) are not usually spotless either. I appreciate there are some tough-to-remove debris like scrambled egg and I accept that, but what bothers me is the performance I have now is far worse than it was a year ago.

Any suggestions gratefully received, thanks.

 

[Tigercubrider]

How often have you cleaned it? Using a dishwasher cleaner?

 

[dogfonos]

Forgot to add that it's been cleaned twice using dishwasher cleaner. Machine never looked dirty though, even in the pump compartment. First time it was cleaned after around 9 months when things were fine. Second clean was about 3 or 4 months ago and was done in response to failing performance. The performance didn't improve afterwards. The machine has a 'machine care' program which I used.

Should say that the machine is used, on average, three times a week.

 

[Burnerman]

Do check the spinning arms for rice grains or whatever stuck in the nozzles.
If you open the door mid washing cycle you should see the arms spinning to a stop and get a blast of steam billowing out of the door.....have you tried this?
John

 

[dogfonos]

Do check the spinning arms for rice grains or whatever stuck in the nozzles.
If you open the door mid washing cycle you should see the arms spinning to a stop and get a blast of steam billowing out of the door.....have you tried this?
John

No, I haven't, but I will, thanks. The sound when the machine is running suggests at least one of the spray arms is spinning. Just now, I started off a vinegar wash (on the machine care cycle - 1.5 hours, 70C) because, although the machine is completely clear of food debris and stains - always is - there is a very fine, powdery white film on some internal surfaces which looks like chalk. Can't imagine how it might affect performance to this extent, but you never know.

The water channels through the spinning arms and all connecting pipes within the machine look clear, as far as I can see (no white film either). I have reverse flushed the spinning arms but they were spotless and always have been to date.

No visibly dirty item is placed in the machine. I get the p*ss taken out of me when others see me clean stuff before I load the dishwasher. I doubt so much as a grain of rice has ever been loaded into this dishwasher and that's why I find the performance drop-off particularly galling.

 

[Burnerman]

Curious - Bosch stuff is always my choice and I’ve had no problems.
I’d suspect low pump performance though - this determines the speed of the arms, and could be the problem.
White deposit wise, I sometimes get this on glasses when low on rinse aidbut I’ve never seen it anywhere else!
John

 

[dogfonos]

I’d suspect low pump performance though - this determines the speed of the arms, and could be the problem.

Me too. And if I hadn't tried a top-end tablet and had similar poor (slightly worse, in fact) cleaning performance, I would also think that the dishwasher tablet composition might have changed.

Did two vinegar washes at 70C because of slight water cloudiness left behind from the first vinegar wash. Machine looks showroom new. Slight coloured 'petrol' type stain markings inside the door have gone as has the powdery film. Looking forward to doing the next proper wash - almost.

I think I'll add a regular vinegar wash to the dishwasher cleaning regime.

 

[dogfonos]

Update: Despite a spotless-looking dishwasher, tea mugs are still coming out with stains. There's no discernible improvement so not a machine cleanliness issue. Both spray arms are spinning so rules that out too. Factors that could still impact cleaning efficiency would be: cleaning water temperature, time in contact with cleaning agent, pump/jet pressure, internal water leaks (i.e. from spray arm joints or upper basket spray arm water connection) or any combination of. Time to contact Bosch.