Olympia Cremina losing pressure due to piston seals? - Page 3

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sixysixss
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#21: Post by sixysixss »

I experienced the same issue with my 74 Cremina. It seemed to occur on mine after the group was warmed up and particularly if the machine had been on for a period of time. I changed the piston gaskets and that solved the problem. Even though you changed them 6 months ago, try putting a new set of gaskets in. Hope that solves your problem.

OldNuc
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#22: Post by OldNuc »

That issue is a piston seal bypassing. If you are using the black elastomer seals they have an alarmingly short service life if you are regularly using the machine. The silicone piston seals last much longer and are not as prone to this bypassing event.

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chopinhauer (original poster)
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#23: Post by chopinhauer (original poster) »

The consensus seems to be it's the piston seals, so I'm going to change them out today for new Olympia OEM black seals. I will also order some of the new OE silicon seals (piston and PF) and put them in next time the seals need a change or if, god forbid, the problem persists. All the other possibilities alluded to by the various posters I've checked off (piston bore is perfect, rod clip seal is fine, etc).

If it is the piston seals that failed early, it might be because I have been pushing the machine pretty hard the last 6 months. I've been grinding a bit finer and really forcing the lever to get slow shots that 'drip drip' a bit more than 'flow' and which have a lowish shot volume (basically 16gram 1:1 ristrettos). Sometimes this leads to overextraction which I don't mind given I dislike underextraction far more. But I guess it could be putting strain on the piston seals even though I try to keep them well-lubed (i.e. every 3-4 months).

I'd really like to stress how grateful I am for all input into this thead. Despite my experience with these machines, and the fact that I ought to be totally on top of them by now, I would going around in circles without the help from other manual lever afictionados who are no doubt more technically au fait then me.

I'll provide feedback when I know whether the new seals have or have not done the job.
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chopinhauer (original poster)
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#24: Post by chopinhauer (original poster) »

OK, after about 20 or so shots with the new piston seals its safe to say that the problem lay in the old piston seals (not OEM but OE seals). For the record, it set in about 6 months ago when the previous OE seals began to fail. I then did numerous things, including eventually changing the seals to new OE black seals). These then, obviously failed quickly. Now I have OEM black seals in and these feel very different and even looked different when I installed them.

So, for the record, and in case anybody else encounters a similar issue I will ask the mods to change the title of this thread to Cremina losing pressure due to piston seals?. This will make searching easier.
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drgary
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#25: Post by drgary »

Glad it's working.

"Cremina losing pressure due to piston seals?"

Done!
Gary
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chopinhauer (original poster)
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#26: Post by chopinhauer (original poster) »

Gary, you're fast and efficient. Thanks!
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drgary
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#27: Post by drgary »

I've got a vintage Cremina with equally vintage OE seals and some roughness in the pull. I think I'll swap them out and will report back. :wink:
Gary
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samuellaw178
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#28: Post by samuellaw178 »

Thanks for the update Robert!

Have you looked closely at the piston seals to see what's wrong? Might be useful for future troubleshooting as well. Did they shrink, hardened, torn, distorted or changed in any way?

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chopinhauer (original poster)
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#29: Post by chopinhauer (original poster) »

The seals looked OK, both the old original ones I took out 6 months ago (which were in at least for 2 years) and the new ones, but both were very smooth, which is to say the open sided lip was was hardly prominent. I don't think this was down to shrinkage but to the original construction. The set I put in 6 months ago was easy to put on in comparison to the OEM set I put on a few days ago. Too easy in retrospect.The OEMs look much the same, but have far less 'give'; meaning they really had to be wedged gradually and gently down with a flat screwdriver (not with one's fingers as Doug does in the OE video. Fingers aren't strong enough to do this with the OEMs). If you don't get them down far enough you simply can't get the piston in the chamber.

Once in, one can feel the difference with the OEMs. The piston has more resistance, even when well lubed, when one raises it to let the water through.

Anyway, I learnt a lesson about piston seals during this ordeal. I alway took them for granted as basically lasting around 3 years and only needing change upon commencement of a leak. Now I know about 'piston seal bypassing' as Rich Goodin (OldNuc) put it in post #22
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