Bezzera Strega squeaking sound eliminated by down-dosing

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doublehelix
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#1: Post by doublehelix »

Been using my Strega for over a month, but recently enjoyed a squeaking sound when extracting-- it sounds exactly like what was recorded in a 2011, or 2012 thread. Seemed a bit early for a lube job. Someone suggested (perhaps, Jim) that maybe over-dosing was at the root of the problem. I can confirm that this is truly the case, since the squeaks appeared when I seriously up-dosed. This was evidenced by NOT seeing flow after the pump went silent; engaging the lever, immediately produced the squeaking sound, and then allowed drops of espresso to appear in my cup after about 5-8 seconds. Squeaking/squealing was eliminated when I down-dosed to something more reasonable.

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ravco
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#2: Post by ravco »

I'm not sure it's the overdosing as such, but rather the high pressure that seems to have built up with your grind-setting ("not seeing flow after the pump went silent"), which probably opened the OPV . When my Strega was new it also squeeked and I was using 14g in a 14g-IMS-filter. Squeeking disappeared with time.

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doublehelix (original poster)
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#3: Post by doublehelix (original poster) »

Indeed...high-dosing precipitates Strega actions and the OPV did release water, as it should. Over the past month, my Strega was squeak-free...it starting singing when I pushed the dosing towards choking. Don't think the puck is making noise.

Also read that the OPV might be making the noise???? Or maybe pressure-deformed piston seals, over-stressed while traveling along the sleeve???? Not a big issue--I'll over-dose and listen carefully for where the sounds are coming from.

The good news is that I probably don't need to re-lube, just yet.

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ravco
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#4: Post by ravco »

I'm pretty sure it was MY OPV squeeking. The noise coincided with water-flow through the OPV and I seem to remember having read other post about the OPV squeeking on the strega.

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radudanutco
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#5: Post by radudanutco »

it should be OPV, as I had some similar weird sound while trying to lower its setting towards 9 bar with a Bezzera Magica;
like here: https://www.youtube.com/watch?v=CKO5Uj61a1U
seems kind of a high pitch resonance of the OPV spring;
then I bought an "OPV kit for 9 bar";

with my Strega, I had that sound sometime when I was working at "full pump", as I use to say for letting the pump reaching the OPV pressure limit; with some wrong dialed-in pucks, and/or not sufficiently preinfused;

now, I am working mostly with "short pump" shots, that is, I let the pump reach an usual 2-3 bar on its pressure ramp, then stop the pump and raise the lever;
(I use a manometer installed at the pump output to monitor the pressure ramp of the pump; also, I can make the ramp last longer, by using a dimmer on the pump)

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doublehelix (original poster)
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#6: Post by doublehelix (original poster) »

Listened to that YouTube.....very different sound from what was posted here:
https://www.youtube.com/watch?v=va0dKzu ... e=youtu.be

This is what I hear....