HomeRoast Digest


Topic: Group Head Pressure question (15 msgs / 376 lines)
1) From: dave
I just replaced my group head gasket today hoping to resolve a  
problem. It has lessened this problem it but not eliminated it. When  
the extraction is taking place the portafilter shoots a single  
streams of coffee in random direction, this occurs with any tampering  
pressures on grounds. I also get a bit of leakage dripping on the  
outside of the portafilter. The extraction is much lighter than it  
use to be and when I back flush, the group head seams to be under  
such great pressure it blows around the gasket, pulsing to the pumps  
cycle, and blows water/steam on the outside of the portafilter.  This  
is a HX Bezzera 99/s machine. I wonder if the pump pressure is too  
much? Would the 3 way solenoid cause this? But, it had worked fine  
just 2 weeks ago.
Any feedback would greatly be appreciated!!
   dave

2) From: Sandra Andina
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I have a Livia 90A, which I understand is Pasquini's rebadged  
Bezzera. I notice that sometimes when using a bottomless portafilter  
I will get random pinpoint sprays of plain water spraying diagonally  
from the perimeter even if there is a perfect tiger-stripe cone  
brewing down into the cup. I assume this must be the result of  
channeling, but I try to do whatever I can to make sure there are no  
spots in the puck where water can descend without resistance from the  
coffee. I too notice that varying tamp pressure, dosing, distribution  
and avoiding tapping seems to make no difference. But it doesn't seem  
to occur with a spouted PF--except if I've been lax about brushing  
out the gasket area, I might get some dripping around the sides.
On Feb 13, 2007, at 11:41 AM, dave wrote:
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Sandra Andina
www.sandyandina.com
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I have a Livia 90A, which I =
understand is Pasquini's rebadged Bezzera. I notice that sometimes when =
using a bottomless portafilter I will get random pinpoint sprays of =
plain water spraying diagonally from the perimeter even if there is a =
perfect tiger-stripe cone brewing down into the cup. I assume this must =
be the result of channeling, but I try to do whatever I can to make sure =
there are no spots in the puck where water can descend without =
resistance from the coffee. I too notice that varying tamp pressure, =
dosing, distribution and avoiding tapping seems to make no difference. =
But it doesn't seem to occur with a spouted PF--except if I've been lax =
about brushing out the gasket area, I might get some dripping around the =
sides.
On Feb 13, 2007, at 11:41 AM, dave wrote:
I just replaced my group head gasket today hoping to = resolve a problem. It has lessened this problem it but not eliminated = it. When the extraction is taking place the portafilter shoots a single = streams of coffee in random direction, this occurs with any tampering = pressures on grounds. I also get a bit of leakage dripping on the = outside of the portafilter. The extraction is much lighter than it use = to be and when I back flush, the group head seams to be under such great = pressure it blows around the gasket, pulsing to the pumps cycle, and = blows water/steam on the outside of the portafilter.  This is a HX Bezzera 99/s = machine. I wonder if the pump pressure is too much? Would the 3 way = solenoid cause this? But, it had worked fine just 2 weeks ago. Any = feedback would greatly be appreciated!!   dave homeroast mailing listhttp://li=sts.sweetmarias.com/mailman/listinfo/homeroastTo change your personal list settings (digest = options, vacations, unsvbscribes) go to http://=sweetmarias.com/maillistinfo.html#personalsettings = Sandra = Andinawww.sandyandina.com

= = --Apple-Mail-7--189089820--

3) From: Barry Luterman
Dave sounds like in incomplete seal. There is probably dirt under the new 
gasket  between the metal and the gasket. Remove the gasket cleat it and the 
metal surface it faces on. Also not sure about your gasket but some have an 
upside and a downside. If so make sure it is oriented correctly and then 
re-install.

4) From: Barry Luterman
clean it not cleat

5) From: Brett Mason
If it won't clean, then cleat it.  Beat it into submission.  Then install a
new gasket that will have a complete seal....
Brett
On 2/13/07, Barry Luterman  wrote:
<Snip>
-- 
Cheers,
Bretthttp://homeroast.freeservers.com

6) From: Patrick S. Harper
If it jams force it, if it breaks it needed replacing anyways.  At least
that is what they told us in the Army.

7) From: Michael Dhabolt
Dave,
Your new gasket probably has some printing in raised rubber (numbers and
such) on one of the flat sides, that is the side that should go up, into the
group head......the smooth (no printing) side is the one that the
portafilter should come up against.  The gaskets frequently have one
chamfered radius...again that is the edge that should go up, into the group
head.  Cleanliness in the metal areas that recieve the gasket is of
paramount importance to not having leakage coming from around the outside of
the PF sealing surface.
The pump pressure shouldn't have changed substantially for no reason.  When
backflushing do you hear the normal pressure release into the drain tray
when you stop the pump?....if so, the three way valve is probably working
correctly.  Does your machine have a brew pressure gauge?....if so, you will
probably see slightly higher(1/2 bar or so) pressure than during a pull when
backflushing.
It really sounds like removing the PF gasket, doing a thorough (and a little
more) cleaning, replace the gasket....ensuring correct
orientation.......should correct the problem.
If not  - - another email to the list.
Mike (just plain)

8) From: Leo Zick
What kind of machine? You could be grinding too fine or over filling the
basket. Lower model krups use this method as their pressure release valve.

9) From: Brian Kamnetz
I sure love your posts, Mike. I wish I knew some (any?) of all the
interesting things you know....
Brian
On 2/13/07, Michael Dhabolt  wrote:
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10) From: dave
Mike(just maybe not so plain),
    Thanks again for your expert advice!!
Dave
On Feb 13, 2007, at 4:24 PM, Michael Dhabolt wrote:
<Snip>

11) From: Michael Dhabolt
Dave,
Advice isn't worth much if it doesn't solve the problem.  Fixed?
Mike (just plain)

12) From: dave
Mike,
Thanks for checking back. I still have the same problem but the  
gasket doesn't leak now.
The shots blast out of the gasket, blonding almost immediately and  
spraying coffee all  over. The coffee moves over the bottom
of the naked portafilter  randomly and no longer forms the small  
steady stream it once did. Temp/grind/tamp doesn't change anything here.
I might take the output tube off to see how much force the pump is  
applying.
Know any good people who would fix this beast?
thanks again!!
Dave

13) From: dave
Mike(just plain),
   Bezzera sent me this response to my problem....
     Hi dave,
The pressure during the brewing is the pressure necessary so that the  
water overcome the coffee resistence.
So if the coffee is made in 5-10 seconds, it means that the coffee  
resistence is not enough, there is something wrong in the coffee milled.
Then the temperatures of water to make a coffee could be too high or  
the pipe line is blocked.
You have to check:
- the pressure of the pump with a special filterholder with gauge
- the boiler pressure (1- 1,2 bars it is correct) putting a gauge on  
the steam hose
- the flow rate without the filterholder (at least 250/300 cc/min)
If the machine worked well, means that now one or more of this  
parameters it isn't exactly.
Hoping to help you, my best regards.
G.BEZZERA
Pietro Roscio
Can you tell me if these gauges are available?
thanks
   dave

14) From: miKe mcKoffee
PF mount pressure gauges are available places like Espresso Parts NW or
Chris's Coffee Service. 
If you're following good HX temp management technique you should be able to
tell if boiler pressure has changed since HX surf will have changed.
Kona Kurmudgeon miKe mcKoffee
URL to Rosto mods, FrankenFormer, some recipes etc:http://mdmint.home.comcast.net/coffee/Rosto_mod.htmUltimately the quest for Koffee Nirvana is a solitary path. To know I must
first not know. And in knowing know I know not. Each Personal enlightenment
found exploring the many divergent foot steps of Those who have gone before.
Sweet Maria's List - Searchable Archiveshttp://themeyers.org/HomeRoast/
 
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15) From: Michael Dhabolt
Dave,
I've sent you an email - off list. Let's continue the discussion that way.
Mike (just plain)


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