Hello, I purchased my espresso machine about 6 months ago. It's a Bezzera BZ13 PM, a HX machine- no issues until last week.

I spent a month away from home, and when I came back to use the machine, there's now a high-pitched noise when it gets around 9 bars of pressure.

I descaled the machine after I learned that might be the fix. It turns out after 5-6 flushes, the sound will go away with the descaling solution, even up past 11 bars of pressure. But as soon as I put water back in the machine and try to use it, I get the sound again around 9 bar.

I've adjusted the OPV down to 9 bars, but that hasn't helped at all. I've gone through the descaling procedure again with a different cleaner with the same results- no noise with a blind filter & descaling solution (after a number of flushes), but as soon as I go back to water I get the noise.

Please let me know if you have any advice, thank you!

Well, shoot, I thought I could help you, but your symptoms are slightly different than mine. I have the high pitched sound only when I approach the OPV limit of 10+ bar. At 9, it consistently pulls a pretty great shot without squealing.