Hi Sergiu
You do not need to remove the small screw with the 220V tag. There is only the large M12 nut under the top cap that holds the boiler to the element base. Once the M12 nut is removed then the boiler should come off. If the boiler has not been removed for some time then it could have scale build up holding it together. It might need you to use a soft hammer to just get it moving.

thank you, that makes a lot of sense!


meanwhile, this is the boiler situation at the moment. i can't see if it's corrosion underneath but that's A LOT of scale or something else (it's soft, can't figure out what is that).

OK - that is quite some scale build up. Citric acid will be the best place to start. Once the scale is gone then it should reveal all the problems and the boiler should come off. Good luck.

i thought citric acid is not the best idea for this kind of boiler, as the scale can avoid spreading the corrosion, and best practice is just trying to remove the external layer of build up (but i can be wrong though).

That's my understanding as well. I'd use a dental pick in areas I need to clear out ( to get to a nut or clear a passage) and then use a rubber mallet for encouragement to separate the two stuck pieces if need be.

You cannot use an alkaline on alloy, it will turn to dust, you can use an acid reasonably safely but I would not soak the whole boiler it in acid like you can for copper. On the inside of my boiler where there was some stubborn buildup I painted on a the citric acid with a brush to soften things up. You need to be very careful when you use a mechanical method to as well. These boilers appear to suffer from deep pits rather than a overall corrosion, so it can get very thin in places.
The pressure cylinder will need to be driven out using a hammer and a long soft metal rod ( I used 40mm Aluminium rod), but you need to support the bottom of the boiler to avoid damaging / destroying the boiler.
It is all possible, but just go slow and let things soak and loosen up, otherwise something could break. Good luck.

Time for a bit of an update on observations so far.
I have seen written on another post that the Microcimbali is temperamental. Well I guess they can be, but that is due to the owners passion or attention to detail. You cannot just set and forget these machines, they need regular basic maintenance.
To get a consistent volume per lever stroke it is critical that the rubber disk valve located under the shower screen is clean and seals. I now remove the shower screen every week and clean the shower screen, rubber valve and the pressure cylinder bottom surface. Coffee grinds do migrate up through the shower screen and build up in that cavity and prevent the rubber valve from sealing.
The pressure valve is more reliable, but with mine the ball gets stuck in the weight and then does not seal. Thus the boiler then never gets to pressure which affects the brew temperature and the pre-infusion. So that now also gets cleaned every week.
The last regular maintenance that I am doing every week is to drain the boiler so that it is dry over the weekend. This machine is my daily work machine. It could relate to the magnesium anode, or that I did not clean the interior of the boiler, but I have been getting a grey sediment. I am presuming (hoping)it is an aluminium oxide that had previously built up on the inner surface of the boiler and is now being shed. The amount of sediment appears to be reducing so I hope that it will reach a point where there is no more sediment. Time will prove me right or wrong.

I have placed a thermocouple on the heater element plate so I can monitor the heat up. I have both the 300w and 1000w elements turned on at startup. Once the thermocouple reads 85C, I turn off the 1000w element and let it reach a steady state with the 300w element. If the 1000w is turned off at 85C then there is no geyser of steam and water, let it go any further and it will erupt.

Generally the heat up is quick and there are no leaks. Sight glass makes it easy to monitor what is going on in the boiler and water levels. Most importantly if I do my regular weekly maintenance then the shot quality is excellent and consistent.

I do not like the standard steam wand orientation. it is too horizontal and I have not been able to get a good micro foam, but that is more likely operator ability. There is plenty of steam, but there is the risk of the geyser, so at this point no milk drinks from this machine.

Another update - I disassembled the boiler to have a good look to see what was happening inside.
First impression was not good. Most of the boiler scale (corrosion residue and calcium) appears to have been shed. This is the residue that was in the boiler!


I then gave the inside of the boiler a thorough scrub with a stainless steel wire brush followed by a rinse out with a high pressure water machine (2000psi). This is the first time I have cleaned the inside of the boiler, and now that it is getting down to whatever base metal is left it is not pretty!
The inside is severely pitted.





At this point I was about to call the experiment a failure, but then I had a look at magnesium anode. It is starting to corrode There are small pits starting to develop on the surface, which is what should be happening if it is functioning as an anode.




I reassembled the boiler, including the magnesium anode. As the boiler was less than pristine when I purchased it, and I did not thoroughly clean it. I have no way to determine if the interior of the boiler has deteriorated. I an going to try it again and see what happens.

By the way, a quick calculation of the boiler pressure relief valve. The weight is 24.3gr and the hole in the valve body measures 3.0mm across. This calculates out to 0.34bar, above atmospheric pressure, or 1.34bar boiler pressure. The boiling point of water at that pressure is 108C, that is a lot hotter than the 93C that appears to be the accepted normal. With the Microcimbali the group is immersed in the boiler so there is no opportunity for the brew water to cool? Would appreciate some input as to why they were designed to operate at such high temperatures?

2nd week back at work after our summer vacation ( Yes our Covid daily infections are down to zero at the moment) so we can have a vacation locally!
As part of my weekly routine I drain the boiler on Friday after my morning shot. More grunge and particles came out in the water, so my confidence in the anode protection is severely diminished.
Per the other post, it is time to consider alternative replacement boilers.
I will keep it going with the anode until I have a replacement, just to see what happens.

Dang. I'm still curious to see the outcome, but I was super hopeful on your solution!