Olympia Cremina losing pressure due to piston seals?

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chopinhauer

Postby chopinhauer » Mar 07, 2018, 4:38 pm

Well, this issue's got me stumped.

I've been using Creminas 73 and 2011 models for 12 years and before that my 1980 Europiccola for 10 years and never has this issue occurred or been mentioned in the forums to my knowledge. It relates to the 2011 Cremina, which I've been using for the past 6 years.

Basically, for the past 6 months every few shots, so intermittently, the lever has no pressure when pressed down pulling a shot; this despite the pressure gauge reading .8 bar (and the fact that I have already run water through the group and it seems to gush out normally). What happens is that after lifting the lever and holding for 15 seconds I push down and there is little resistance and no water/coffee comes out. Them I pump the lever a few times until I feel it 'bite' and eventually a long thin watery shot comes out. These shots always look and taste terrible and always result in a watery puck and residual pressure left over at the portafilter when I release it; viz. portafilter 'sneeze'

In other words, the lever every once and while simply doesn't 'bite' when pushed down. There is no resistance. So what I have tried to rectify this?

My first thought was scale was blocking the inlet hole in the group thus preventing water from coming out. And yes the machine did need a big descale which I performed carefully and thoroughly. Now the water really gushes out when the lever is raised with no portafilter or an empty portafilter, but the abovementioned problem still remains. I used proper descaling solution, not citric, so the actual scale is dissolved so it can't still be there potentially blocking the inlet hole or even the feeder tube from boiler to group. (More on the 'feeder tube' below).

Next I serviced the group and piston gaskets, checked and re-lubed everything. I do this every 3 months anyway because I find the group needs constant lubing and maintenance to run smoothly. The issue is often worse after re-lubing (using Dow 111) which makes me think maybe lube is blocking the inlet hole (not that I put much on, and not that this has ever occurred before in any of the machines I've used over the past years).

Now I'm thinking either the problem has something to do with 'pressure', a 'blocked feeder tube' or damaged/faulty portafilter gasket.

Re the pressure issue, I can't think what it may be. The Mater pressurestat works fine. I can check it with another gauge I can put on the boiler cap which I use with my 73 Cremina. So could it be the internal pressure relief valve. Normally problems here are evidenced by a leak, and there is no leak, or hissing in the machine.

Or is the issue connected with a blocked feeder tube? The tube in the post 2011 Creminas are internal, attached to the boiler and not the group itself (as with the 67 Creminas). So how the hell do I descale or otherwise unblock this tube? I've used descaler to the point that anything in there should have been dissolved and anyway, as I've said, water gushes out when not pulling a shot, so I doubt this is the issue.

And finally, the portafilter gasket. This gasket is the worst thing about the the new Creminas (never an issue with the 67 Creminas). They are a real bugger to put in and can easily get damaged. I gave up long ago with the red OEM gaskets and use either black OEM gaskets from Migg Frei or the old black ones from OE which they don't make anymore. I know when this gasket is faulty or damaged because it leaks. But maybe it is faulty, and while not leaking is still somehow letting air in. I don't know. Just an idea, but given the nature of the sharp edges on the group and the hassles installing these gaskets this could be the source of the issue.

So all up, any ideas? Apologies for the long post and thanks to those who have got this far. Is anyone able and/or willing to tell me whether I've missed anything, because surely this annoying problem is solvable?
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samuellaw178
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Postby samuellaw178 » Mar 07, 2018, 5:46 pm

Hi Robert,

You mention:
chopinhauer wrote:(and the fact that I have already run water through the group and it seems to gush out normally)


So it sounds like the issue is on the pressure building side - which relates to the piston/cylinder assembly etc, and likely not the portafilter gasket either. Have you replaced the piston seals with new ones, other than performing the lubrication? Have you checked if the cylinder wall is smooth/intact?

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chopinhauer

Postby chopinhauer » Mar 07, 2018, 9:32 pm

Thanks Sam, but my answer is 'yes' to both. Put new gaskets in a few months back and the cylinder walls are pristine. Rough cylinder walls were often an issue on my MCal (leading to a jerky lever action), but never had an issue with them on my Pavoni or Creminas, the latter of which are very forgiving machines in most respects.
As for assembly, I think I did it properly and maintain it properly. I am an old hand at these things, which is not to say bad habits and techniques don't creep in. But I am fairly careful.
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samuellaw178
Team HB

Postby samuellaw178 » Mar 07, 2018, 9:55 pm

Hmm,tricky indeed. How about the least likely ones, are the seals orientated correctly? Do the new seals fit in the cylinder snugly like the old seals?

Based on what you mentioned, the water is filling up the cylinder, but the pressure is not building up. Doesn't seem like there's much else to go wrong other than the piston seal...
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chopinhauer

Postby chopinhauer » Mar 07, 2018, 10:20 pm

Ok, so you're thinking it isn't anything to do with the various paths the water takes into the group (so not scale or a blockage). In which you're probably right it is something do with the piston seals. I'll open her up again in an hour or so (I just pulled another abysmal shot) and check it out and then report back in a day or so after I've pulled enough shots to know where the issues stands. If it were the old Cremina I wouldn't mind opening her up, but the new one, given how hard it is to reinstall the group gasket, is a real pain in this respect.
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drgary
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Postby drgary » Mar 08, 2018, 2:42 am

Hi Robert,

Sorry you're encountering this. A few years back I had a Zacconi Baby that wouldn't hold pressure when pulling shots. It had me stumped until I figured out the portafilter ears had worn down, so the portafilter wasn't always seating properly centered on the portafilter gasket. I had issues with a La Pavoni Europiccola where the portafilter gasket for my machine required a slightly different thickness than the portafilter gaskets on the same generation but other years. If you're having an intermittent leak somewhere, it could be the first problem just starting or the second, or a combination, since locking in the portafilter creates the pressurized seal.
Gary
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chopinhauer

Postby chopinhauer » Mar 08, 2018, 3:46 am

Thanks Gary, your intuition that it has something to do with the portafilter lock in seems to be correct. In my case, it isn't the PF ears, which are OK, but it is good to know that they can be the source of the problem.

I did get into the piston to check the gaskets and they were fine. But I think I had put my portafilter gasket in incorrectly which was probably the source of the problem. It is one of the old black OEM gaskets with one flat side and one slightly curved side. The OE black ones have two flat sides. I think I put the curved side facing in, instead of out. When the problem stated 6 months ago I changed this gasket which, at the time was damaged so also was probably the cause of the problem (but I didn't know it since the machine was so clogged with scale that I attributed the lack of pressure to inlet hole blockage). And when the problem persisted with the new PF gasket I didn't think it could be source because normally an ill-fitting or damaged PF gasket results in leaks and it my machine wasn't leaking

Anyway, I have pulled a couple of shots a few hours apart since re-installing the PF gasket and so far both were fine in that the machine performed properly. I'll know whether the problem is solved after I've pulled another 2 or 3 shots tomorrow.

Overall though, I'm glad I posted and got yours and Sam's feedback. It made me realise the problem wasn't scale or some of the other possibilities I mentioned. Therefore I didn't go through the pointless routine of yet another descale or investigate under the case of the machine. Your posts help me focus on the real source...I hope.
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chopinhauer

Postby chopinhauer » Mar 08, 2018, 11:21 pm

Problem resolved. It was the PF gasket all along. When the issue first arose I changed the PF gasket which was damaged (but not such as to cause a leak). But I also did a plethora of other things. But unfortunately I put the new gasket in curved side up instead of down (see my immediately preceding post). This too didn't result in a leak (which would have alerted me to my negligence) but elicited the same behaviour as the previously damaged gasket. Strange because leaks are the usual sign of a problem with the gasket, or lots of coffee grit. But not loss of pressure (evidently due to air getting in).

Anyway, I'm happy as the Cremina is back to her consistent and controllable old-self.
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drgary
Team HB

Postby drgary » Mar 09, 2018, 2:21 am

I'm glad to see a happy ending! :D
Gary
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samuellaw178
Team HB

Postby samuellaw178 » Mar 09, 2018, 2:29 am

Yes, great news, must be a huge relief! This is a bit mind-boggling though, still trying to picture how this could happen. :P I would have expected the pf to leak catastrophically (>60ml/30sec) for the piston to not have any pressure. Anyhow, all that matters is it's fixed now and the espresso is flowing!

Enjoy!