A.F.X. Images

WMF Espresso Cleanup

Update 2008

This is an old article from 2004. I keep it around as reference for others who are interested in restoring older commercial espresso machines.

The only enhancement I implemented was a boiler insulation which saves about 15%.

The machine is in daily use, brewing espresso based on Monsooned Malabar from Caffé Fausto, it performs well and I would not want to be without it.


Cleaning up a 1 Group WMF Espresso (a Cimbali M30 Bistro in disguise)

I got lucky on e-bay and bought a WMF Espresso 9503 for a reasonable price. This is a commercial espresso machine built by Cimbali for WMF. It has a slightly different exterior (more stainless steel, black bottom instead of gray and blue buttons instead of green ones) and a slightly different internal tubing (cold water is through steel mesh enforced and insulated flexible tubing instead of fixed copper pipes) but is otherwise identical to the Cimbali M30 Bistro. The machine is no longer sold by WMF, they seem to focus on super-automatics only for their professional line.

The machine was built in 1992, and seems to have been used in the army until 2002, then it was stored in a (thankfully heated) garage until I bought it. My first attempts at starting it up lead to the boiler filling and heating, but no pump activities when pressing the brew button. Water came out, but that looked more like line pressure. Steam and hot water where working. The programming of the buttons would not take.

With the help of a fellow espresso freak I started to look closer (the picture quality is not necessarily briliant, they where taken with a PS digital to have a reference for reassembly).

We took apart the pump (a 24V Ulka). The steel piston was not moving in it's brass enclosure. So I figured, if the pump is already blocked by scale the rest of the machine is probably totally scaled up.

We started taking pictures and took the machine apart. This is where we made our first error. We did not take enough pictures of the individual components that where taken apart, thinking that placing them into their own boxes each would be sufficient. It would have been better if we would have taken also pictures of the disassembly of the valves and flow restrictors....

The next step was to clean out the old coffee remains and the scale. We used about 1Kg of citric acid and quite a bit of Puly Caff. Unfortunately, when soaking copper tubing together with other metals in citric acid, the other metals (brass, nickel, some steels) will aquire a copper coating, especially if there where already traces of other things on the metal. If you do not leave the parts in too long, this will be no issue, if you leave them a little bit longer, you can still rub off the coper sheen. If you leave them too long, the copper will be there permanently. Not really a functional problem, but not nice looking and a potential source of verdigris.

De-scalers based on formic acid might be better suited for dealing with copper based tubing. Acetic acid (vinegar) is generally not recommended for coffee machines.

I wonder if that machine ever was de-scaled or cleaned during its time in service. They guy I bought it from did not have the water softening cylinder that WMF ships with the machine by default. The water dispersion plate below the shower screen was so strongly glued to the group head with coffee residue, it took three runs with a coffee cleaner to get it off. It really helped to use a little pipe brush to clean the insides of the brew head, I could still extract coffee remains after the three coffee cleaner runs.

Getting new seals and gaskets should be easy. Unfortunately it seems to be particularly hard or expensive to get technical information on the machine. I paid 10€ (plus 10€ UPS COD) for 5 photocopies/prints of the machine sketches with spare parts numbers but no textual description that I received from the local Cimbali dealer.

Other manufacturers have complete spare parts listings and machine drawings online....
Thankfully, there are helpful people online, a big thanks! You know who you are ;-)

I sketched my own hydraulics diagram as a reference.

For the 1/8" connectors around the pump and the water inlet I used Loctite 542 as Teflon tape will not allow you even the slightest readjustment...

Even after cleanup, the pump would not work, looks like the coils where fused, so I started looking around for a new pump. There are not too many 24V vibe pumps available. I ended up ordering a 48W Fluidotech after some research. The ULKA would have been cheaper, but the Fluidotechs are built for continuous operation whereas the ULKAs will die if run for too long. In addition, the Fluidotech has a higher flow rate, not on par with a rotary, but higher than the ULKAs. Of course, I also considered a rotary, but apart from one online suggestion without any hints on how to really do it everyone I asked said don't do it, too much of a hassle. After having read the comparison of two Cimbali Juniors, one with vibe and one with rotary that produced indistinguishable shots in blind testing, I figured it is not worth the hassle and money to go for a rotary.

Of course I am vain, so I bought new style Cimbali handles for the portafilters. They look and feel so much better than the old ones ;-}

I also bought the current Cimbali baskets. Much bigger than the old ones, especially the 1 shot basket.

A new steam wand is on order. From the third party suppliers it is not really clear which one to order for this machine, but that will be solved pretty soon I hope.

Initally I had a third party square brew gasket. Since I switched to the conical original Cimbali gasket, the machine is less prone to leak at the brew gasket and it takes less force to tighten it.

Was it worth the hassle

That depends on your point of view. After one week, the machine seems to be more picky than the Oscar and the results are not noticeable better when it comes to espresso. Steaming on the other hand is faster and easier than on the Oscar. The chrome "three holes around one center hole" Cimbali steam tip is great.

I'll write more once I had enough time to really become familiar with the machine. One thing that is surely different from a tank machine is the influence of the cold water that comes in once the HX and the internal piping has been completely replaced with fresh cool line water.

The baskets knock out a bit cleaner than the La Marzzocco baskets that I have been using on the Oscar.

Having a system connected to the water line and drain is a huge convenience factor!

Not having to listen to the vibe pump filling the boiler when the timer comes on in the morning is also a really big plus.

Planned modifications

Boiler insulation
Whereas newer Cimbalis have it, all the old ones have naked boilers, producng lot's of waste heat (the heater switches on for 8s every minute at the moment). I was thinking about glasswool wrapped in aluminium foil, but gave up on the idea, I think it is too messy. Right now I am trying to find the insulation material that is used in solar heating system. This is supposed to withstand much higher than boiler temperatures.
Bottomless PF
I played with a borrowed bottomless PF for a while. Great. I want one too. It is so much easier to see tamping/packing errors. And it gives me more crema to mix in with the milk.
Boiler drain valve
Currently the lowest boiler opening is just blocked by a screw. That should be easily replaceable by a drain valve even though the parts list doesn't show one. Other Cimbalis have it, so it should be easy to find it. That valve could then be connected to the drain, making it easy to completely drain the boiler.
Heater control lamp
Currently the machine only shows that it's on and when it is getting new water into the boiler. I would like to have an indication of the heating element working as well.
Are there any dual lights available that would fit where the power light is?
Yeah, I know it sounds crazy to PID a Cimbali, but that would allow me to easily adjust the temperature for different roasts vs. opening up the side panel and, turning the presostat screw and hoping I hit the right amount the first time.

Machine parameters

Power rating 1.9-2.3kW
Total boiler capacity 2.5l
Nominal boiler water capacity 1.02l
HX size 0.17l
Shipped pump 24V Ulka vibration pump
Replacement pump 24V Fluidotech "mono" vibration pump,

Useful links

Manufacturers and parts suppliers

Espresso related web sites

Other machine restauration projects

© Andreas Siegert 2004

Last modified: Fri Oct 1 23:00:28 CEST 2004

All content Copyright Andreas F.X. Siegert