# Bezzera BZ02 anti-vacuum valve normal operation



## jpaul__ (Feb 19, 2016)

Hi,

new owner to a previously loved Bezzera BZ02 I have been doing some descaling/inspection.

[biography 15 years with Audrey (Silvia predecessor) these seem rare now ? - purchased in Italy Ventimiglia

I recommend Casa del Caffe as coffee supplier ]

Does the video of the anti-vacuum valve as the machine comes to pressure show normal operation ?

I am concerned about the amount of sputtering, which could give some internal vapour on the internal

electric components. I cleaned the valve that has a small 3-4mm (Teflon ?) O ring on brass spigot (that rises)

which mates against another Teflon ring, so do not know if O ring has worn






Also for valves on water and steam taps , this is what I pulled from the machine,









the cups holding the washers have some damage due to over tightening, but are not leaking

It seems I have to replace the complete spindle although I wonder if washers are, anyway, a very tight fit

and new ones may quickly go the same way ?

[other incident en-route

- broke one of the spigots when removing the push fit side panels - a very tight fit, I will grease these on re-assembly

- water tank removal needed a lot of force, I have now greased O ring, but am not sure if there is a nack to this, eg.

first push down gently ? I was dis-assembling lower level connection as a last resort before I finally applied enough force

to remove tank

]

Cheers,Paul


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## Norvin (Sep 10, 2014)

Good timing, I have two BZ02's disassembled on the bench at the moment.

The anti vac valve plunger cants quite a bit to the left, suggesting a very loose fit in the housing, but if it works... Both housings on my machines are shiny metal, suggesting that they are replacements, so perhaps wear is a problem. They are cheap enough.

I have four spindles, none of them have split like yours. Again, if it works...

The clips are brittle now, 11 of the 24 on my four panels have broken. Reassembling with grease ( I plan on using copaslip) would be a good idea. I haven't worked out what to do about mine yet.

The water tanks are hard to pull off, even after putting some vaseline on the seals. I plan on leaving them in-situ and filling with a jug.

One issue I am currently dealing with - the OPV is non adjustable, the pressure is too high. I have adjusted one so far to give 10 bar by adding shims (thin washers) under the top plug. Beware of the small hole in the standard portafilter, hidded under a lug, that prevents using a portafilter mounted pressure guage unless plugged with a small screw. Oh yes, what fun I had before finding that. My, how I laughed.

Good luck with your restoration.


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## jpaul__ (Feb 19, 2016)

Norvin,

Thanks yes I had not realised brew pressure is not adjustable.

I have not taken this valve apart (for any machine), where should the shims go with respect

to schematic ? (if I have the right one taken from Bezzera parts pdf's - moderator may suppress )









I have not searched for other threads (like the gaggia ones), so maybe this is already explained.

Do you use washers, cut an old feeler gauge

Paul


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## jpaul__ (Feb 19, 2016)

Norvin,

I subsequently searched and below thread suggests brew pressure can be changed by spring pressure

applied by rotating fitting 1 (above spring)

[Without having opened it up and with your comments, I assumed mechanics of fitting would preclude this]

http://coffeegeek.com/forums/espresso/machines/436309#436309

Paul


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## Norvin (Sep 10, 2014)

Put them above or below the spacer (part 3) to reduce the pressure, the description suggests the inner dia is 12.2mm, outer dia doesn't matter. Making a longer spacer out of tube will also do.

A few mm is all that's needed (well, it was on the one that I did). Washers will do, you may be able to reduce the thickness by rubbing them down with wet & dry on a plate. It's a bit laborious but you should only need to do it once. I haven't seen this technique mentioned in any OPV related thread.

Feeler guage shim is wrong shape and you won't be able to cut a hole in it, you won't need that level of accuracy anyway.

edit.

If you just rotate 1, it will be loose and leak.

Further edit.

The water in that part is not pressurised, so wrapping thread with PTFE tape may just work, I've never tried it.


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## Dylan (Dec 5, 2011)

That is not unusual spitting insofar as I have seen similar on other machines I have had the covers off, but I have not seen one on a 'new' machine to know as reference what it looks like when new.

I had the covers off a friends Oscar just the other day and the spitting was worse than this, something I meant to look at as it is indeed concerning around high powered electrics.


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## DavecUK (Aug 6, 2013)

Dylan said:


> That is not unusual spitting insofar as I have seen similar on other machines I have had the covers off, but I have not seen one on a 'new' machine to know as reference what it looks like when new.
> 
> I had the covers off a friends Oscar just the other day and the spitting was worse than this, something I meant to look at as it is indeed concerning around high powered electrics.


I reckon you could leave an old rag and throw it in there to soak up any water, then put the top on the case.............would probably work real good until it caught fire...at which point you simply replace the house and machine.


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## jpaul__ (Feb 19, 2016)

Dave,

prior to taking cover off, descale, checked probes, cleaned anti-vac, checking thermostat operation, the machine had

thrown the earth trip/rcd; still unexplained , so I am not leaving it on its own yet; I have not cracked open boiler.

statistics on mortality due to coffee machines would be interesting (adverse impact of caffeine ....)

Paul


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## jpaul__ (Feb 19, 2016)

I replaced the group bell housing on bz02 to change from pod to a conventional portafilter.

I learned a good lesson (do not trust internet) - supplied group gasket was bevelled, so after researching

http://www.coffeegeek.com/forums/espresso/0/586307 I installed it

with the flat surface against the portafilter. I found portafilter would not fit (too tight)

I then realised it is actually described as conical (so per only advice I could find on Marzocco gs3)

the cone shape should point towards portafilter.

After half an hour with a butter knife managed to extract and flip it, and now portafilter fits,

[ fortunately had some mineral oil on the filter when I installed it but I had bedded it in well

with initial try]

Down the line the conical gaskets seem less easily available online, but do you have any opinions on

their relative useful leak free life-spans. ?

Paul


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## jpaul__ (Feb 19, 2016)

For the bezerra anti-vacuum valve spluttering as pin pops out on warm up, I saw that simonelli

Oscar seems to have a copper shroud to prevent water be distributed in machine internals,

see here so am wondering whether to solder a piece of metal to build something similar.

Or there seem to be other (more modern?) anti vacuum valve types that would maybe alleviate

the problem permanently see here ... or I have not yet pulled the complete unit from boiler (just descaled the

pin and valve) and I need to do that first ?

[i am currently running machine with top cover and sides off in the interim, but think if the copper innards

were polished and Perspex covers installed this could have an air of the pompidou centre or the original imac ?]


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## jpaul__ (Feb 19, 2016)

This seems an even better option an anti vac where you route 'exhaust' with a silicone hose back to reservoir ?

anyone tried one of these ? I will see if I can source one at reasonable price in uk.


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## Norvin (Sep 10, 2014)

I would replace the faulty valve with a new one, cost about a fiver.

The small amount of water that escapes prior to the valve shutting will evaporate quickly on the surface of the hot boiler.

If you did want to put a disc under the valve to catch the water, a dished washer would do. I don't think that soldering would work as you wouldn't be able to get the surface of the boiler hot enough to take the solder. It's large thermal mass would rapidly conduct heat away from the area.


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## espressotechno (Apr 11, 2011)

All anti-vac valves splutter a bit until the pressure buildup closes them. Some have a plastic / metal cup surround to catch excessive splutters, which then evaporate...

All group seals have a bevelled edge for ease of fitting (Cimbali & Reneka seals are inserted the "wrong" way round).

On commercial machines, group seals need replacing every 9-12 months. If not, they leak & turn into concrete.


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