Microcimbali Rebuild

Equipment doesn't work? Troubleshooting? If you're handy, members can help.
User avatar
Coz

#1: Post by Coz » Jul 06, 2012, 6:13 pm

Image

In an effort to step up my home coffee game and get my handyman hands dirty in the process I've bought myself an older (guessing 70's) Microcimbali as a rebuild project. I've recently moved to London from Sydney via Melbourne so am keen to try and recreate some of that hometown magic here. The coffee scene in London has definitely blown up since I was last in town but I am still short of a local (ie: morning coffee run) shop I can rely on to push out a decent coffee. My experience is fairly limited aside from a super enjoyable (and caffeine charged) night class with Benny at The Little Marionette, so am hoping this resto will be a good starter to help get to know the ins and outs a little more.

The machine is in relatively unknown condition so am hoping I don't run into any irreparable issues as I strip the machine down. Nothing seems beyond repair, but from half restoring a classic car I know looks can be deceiving! It's a cool looking machine... I fell in love with the look of the thing first, and after reading up a little bit about it I was still not put off getting myself one as a resto project. It only marginally beat out the Caravel due to the steam wand so fingers crossed I can get that up and running at full strength.

I have only today pulled open the boiler to get a look at how bad the scale inside is. It's thick but fairly isolated from looking at other restorations. I was happy to see the lip of the boiler is tact when I eventually separated the boiler from the base. The instructions from Doug were a huge help in nutting out how that is done. Easy once you know how.

Image
Image
Image

After I complete the full tear down, tackling that scale is my next task so I need to read up on how to best get that off. Open to suggestions/advice in the meantime. My main concern is finding the right solution to remove the scale without stressing or damaging the boiler.

Anyway, enough background, time to get fixing!

Cheers
Corey

rick_bond

#2: Post by rick_bond » Jul 07, 2012, 8:39 am

Got to love a microcimbali!

My advice would be not to soak the boiler in any sort of descaler, the scale looks quite loose and you should be able to scrape or brush alot of it off with a stiff brush. If you soak it in acid, the exterior aluminium will discolour and you'll have to sand and polish it back - hours of work!

User avatar
Coz

#3: Post by Coz » Jul 07, 2012, 11:31 am

Thanks Rick, will give that a go. It is fairly loose throughout so there's a good chance I can get the bulk of it off before hitting the acid. Less polishing the better! Looking forward to seeing more or your Bo-ema rebuild.

Cheers
Corey

User avatar
drgary
Team HB

#4: Post by drgary » Jul 09, 2012, 9:47 pm

You might consider not descaling the boiler as the scale may create a protective coating. Descale the heating coils of course and the inside of the cylinder. But if you take the scale off you may expose the aluminum to more corrosion which can badly pit and eventually destroy the boilers of these machines. Also, a sacrificial zinc anode can help retard corrosion.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

User avatar
drgary
Team HB

#5: Post by drgary » Jul 10, 2012, 1:48 am

Corey, a few of us created a fairly long thread on restoring these that starts with discussing the boiler. Then I provided some detailed documentation of my rebuild. That thread is here.

Related to this, I also created threads about care and feeding of aluminum boilers and rewiring a Microcimbali.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

User avatar
Coz

#6: Post by Coz » Jul 11, 2012, 1:08 pm

Cheers Gary. I had a good read through your posts prior to buying the machine, you did a great job. Really well explained info, thanks for sharing your findings so thoroughly. I'll be referring back to those throughout my build no doubt.

How far to take the descaling is what I'm working through at the moment. I'm thinking at this stage I'll start with a non chemical removal of the bulk scale in the boiler, and follow a similar approach to how you went about cleaning the cylinder. I'm not in a rush to remove the cylinder and would prefer not to if at all possible.

The heating coils are heavily covered so need to get my approach to that sorted. Is the coil assembly and base soak-able?

Cheers
Corey

User avatar
drgary
Team HB

#7: Post by drgary » Jul 11, 2012, 2:14 pm

I'm not sure if I would recommend descaling the boiler itself. Before selling my Microcimbali I made the error of scrubbing the scale out of the boiler and the new owner struggled at first with aluminum oxide shedding in dark bits into the water. Based on that I'm thinking it may be better to leave most of that scale as is. I would clean the cylinder of course and the glass sight window and maybe use a pipe cleaner in the steam wand. Be aware also that descaler can degrade chrome. For the base, don't immerse the bottom electrical connections in descaler. What I did was turn the base upside down so the element was suspended in descaler at the bottom of a glass container. I'm not sure but think I either used a 1 quart Pyrex measuring cup or a small glass bowl. This will treat the coils and avoid wetting the other side. In any case, when I fixed the terminal and wired it up, my Microcimbali worked reliably.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

User avatar
Coz

#8: Post by Coz » Jul 11, 2012, 3:03 pm

Got it, thanks for the coil info. With the scale quite powdery I'm wondering if there's anything I can do to stabilise it if it's going to stay in there. It's flaking off the coil as I poke at it now so it's doesn't seem to dug-in.

Cheers
Corey

User avatar
drgary
Team HB

#9: Post by drgary » Jul 11, 2012, 3:40 pm

Coz wrote:With the scale quite powdery I'm wondering if there's anything I can do to stabilise it if it's going to stay in there. It's flaking off the coil as I poke at it now so it's doesn't seem to dug-in.

Cheers
Corey
Corey:

I don't know what to recommend with that. Maybe someone else can chime in.
Gary
LMWDP#308

What I WOULD do for a good cup of coffee!

User avatar
Coz

#10: Post by Coz » Jul 12, 2012, 11:18 am

Last night's boiler teardown went quite well, managed to get everything I wanted off and apart fairly easily. Removing the piston assembly from the boiler body was the only part that gave me much resistance. Looking at it I had to double check the info on the forums and OE to check I wasn't forgetting a screw. I was really conscious of damaging the boiler and or the piston top housing so just took it slow and steady. What worked in the end was somewhat unorthodox but got the job done. After failing to wedge anything between the two parts I lightly hammered a throw away knife blade in where I seemed to be getting the most movement. I repeated this a couple of to both sides and sure enough I got enough daylight between the two parts to fit a screw driver. It was easy from then on in. It wasn't until I had popped it out of the boiler that I a realised where the resistance was coming from. If I were to do this over I would probably try to loosen the piston from the cylinder with a lubricating spray to make the separation easier. With a more maintained machine this is probably not such an issue.

Now knowing the boiler in ok shape I'm tossing up whether to take the cylinder out too. Was happy nothing was broken in the process, all the danger spots on the boiler seem to be in good condition so thinking it might actually come together quite nicely.

Image
Image
Image
Image
Image
Image
Image
Image
Image
Image
Image

I'm a sucker for a teardown shot so took a progress photo of the boiler gear minus the coil assembly. Think I'll clean and replace the seals on this lot first and then tackle the coil and base.

Image

Having spent the night reading up how to best clean the aluminium boiler inside, I'm entirely paranoid now about cleaning the boiler at all for fear of ruining the aluminium. I can't find a definitive answer on what to clean each metal with.

Can anyone recommend what I should use to get all the exterior grime and dirt off? More specifically -

Top piston housing (I'm assuming this is aluminium?)
Piston spring
Brass piston end
Brass cylinder housing and screen
Boiler exterior, including the grimey top which looks like a fiddly job to clean by hand
Chrome friendly cleaner to soak off 30 years worth of coffee off the portafilter housing

As per Gary's advice I'll be using Dezcal for the coil. For the remaining chrome fittings I'll be doing the ol' aluminium foil trick. This thing needs a real deep clean so just want to make sure I've got the right stuff before I go hard at it.

Cheers
Corey