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bigdaddywayne

Bezzera BZ99 pressure problem

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had a 'sticking' drain valve that I took apart and checked the seals on. I've put it back together and now there's not enough pressure to the grouphead to pour a shot. It's been descaled etc and there's plenty of steam coming out of the wand when I trun that on but deffo not enough pressure to pour a shot.

 

When I stop the shot there's a fairly strong 'dump' into the drip tray

 

Pump was replaced about 6 months ago

 

Any thoughts? thanks for your help

 

Wayne

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I believe there is a three way solenoid valve on this M/ch, from your explanation and descaling, it sounds as if there could be a partial blockage in the S/valve. The blockage would build up the pressure from the pump and then discharge it through the over pressure side into the drip tray, hence the sudden gush when you release it.

If this is the cause it requires the S/valve removed stripped and cleaned of any scale/grit particles.

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many thanks for the reply - stripped the solenoid valve and all the lines in and out, took apart the grouphead, all seem very clean. run the machine from cold with the steam wand open to avoid any airlocks.

 

I've noticed that if I run water through the grouphead without the portafilter then there's a heck of a lot of steam and not the waterflow I'd expect

 

any more thoughts? thanks again

 

Wayne

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Try removing and cleaning the water level probes in the top of the boiler. Have a look at the pressure stat for any corrosion evidence of over heating. Examine the thermic device (over heat cut out) on the bottom of the boiler. Also check anti vac valve.

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chhers for the help so far, I had an opportunity to explore a bit further today

 

When I was checking the lines out of the pump this part just pulled out [no force was applied]

 

It looks like it's snapped but I could be wrong as I know there's one or two fittings that can be held by this - seems odd when it's the direct line out of the pump tho

 

any thoughts?

 

cheers, Wayne

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That definitely looks like it's broken - looks as if it was originally brazed together. I'm guessing that if you put it all back together, you're going to get an almighty flood when the pump pushes water through that piece!

Back to your original problem though....what do you mean by the "drain valve"? Expansion/OPV valve? if yes, that could be the cause of slow/little flow through the coffee. The issue of steam coming from the group head - not uncommon: does it resolve into water after a few seconds of running? To overcome this is the whole point of "temperature surfing" - if the machine is idle, water in the heat exchanger can easily get way too hot.

Finally - have you actually tried running a shot, or are you just guessing that the pressure is lacking? It's quite hard to judge by just looking at the flow from the shower screen whether the preessure is right. As a rule of thumb, try running directly into an espresso cup with no portafilter - should fill the cup to the brim in say 10 secs or so.

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the bezzera has what they call [according to their schematics] a safety valve [2.5bar] and a separate drain valve on the top of the boiler unit - the drain valve has a 'floating' seal that pops up when the boiler is getting up to pressure - that had got stuck and was letting out a fair bit of steam and water - that's been cleaned and is working effectively now.

 

Steam out of the grouphead is pretty constant and the flow, without a portafilter is taking 50-60 seconds to fill an espresso cup.

 

Did try running a shot through and it took about 40 seconds to get the smallest of dribbles and the puck was not even fully moistened

 

cheers, Wayne

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