Two days after descale: BEZZERA BZ10, 1.5 years old.

Pump fluctuations with OPV set to 9 bar during extraction, and struggles to reach 12 Bar with blind basket (OPV set above 12 Bar) Bezzera BZ10. It reaches 9 Bar fine with blind basket and OPV set to 9 Bar. During fluctuations with the case removed, the pump can be heard changing the pitch of the vibration, like sometimes it puts out enough pressure, and sometimes it gives up.

Please watch my two youtube videos about my BZ10 malfunctions:
What should I do? Replace the pump? Or take it apart and the OPV and soak them in acid overnight??

Kind regards,

James.

images below: OPV taken apart (advice from Jim). I'm going to soak the parts for 24hrs in DEZCAL.

Ok, I'll try that. Thanks mate.

another_jim wrote:Unscrew, clean, and rescrew the OPV; it's sticking closed then popping open. That's usually a sign of some grit in the works, a common glitch.

With the blind filter in and OPV set to 9 Bar, it works fine. Why is it only during an extraction that I get these fluctuations?

Looks like you are right Jim. See the new photos I put up. But I'm not sure if that white stuff is scale or some sort of thread sealant or lock-tight or something. There is definitely a build up of gunk on that little thing which apparently is a gasket holder according to the IPB.
If this doesn't work I'm going to order a new pump, but it's good that I'm cleaning the OPV because I sometimes get that high pitch squealing noise with the blind basket in, so yeah.
This guy had a similar problem to me, and it turned out to be a failing pump:

Andreja Premium: Pressure gauge fluctuates during shots only

but I thought I should clean this valve out first before I spend $40 on a new pump.

Thanks for your help btw, I really appreciate it.

That "white stuff" is thread sealant. Bezzera has a large presence in Australia so you could always try to duplicate that sealant by contacting the distributor. You might also try to find out if your particular BZ10 has the 9.0 bar kit installed. Bezzera offered this as an option as it appeared in their older accessories catalog.

The long leg of the cast tee houses the OPV . . . just from your pics, it looks fine. The short leg houses a check valve (flow to heat exchanger) and I would assume that even though some adjustment is possible, it gets screwed all the way in. If you end up sealing the threads of the OPV adjustment with Teflon tape, start with the valve conservatively adjusted and adjust in until you hit 9.0 bar with the blind filter. If you adjust the pressure to 9 bar with a blind and you still have fluctuations while producing a shot, it is likely a pump problem.

This adjustment with a blind filter sets the MAXIMUM pressure you should ever see.

Hi Eric, thanks for that info mate.
What exactly does the 9 Bar kit do? Does it just limit the max pressure to 9 Bar? My machine can be set to 12 Bar is seen in one of my videos. That video is with the OPV set way above 12 Bar. Notice it takes ages to climb above 12 Bar with the blind basket in.
I have seen images of the kit on 1st line espresso, and it doesn't look like my machine has got it. I'm interested though.
I'll probably just put Teflon tape on the threads because the Bezzera shop is closed for the holidays.
I think cleaning this valve might actually solve the problem, because that little gasket holder I was talking about before, is the part that actually pushes against the spring tension. It had a decent amount of gunk caked on one side as can be seen in one of my pics. It's been soaking in citric acid for about 4 hours now and it's all clean. I'm gunna soak it overnight anyway though just in case.
If this doesn't solve the problem, I'm going to order a new pump.

What exactly does the 9 Bar kit do?

I cannot answer this with any technical accuracy. I suspect it included a different spring and was developed by some influence from Bezzera distributors. Setting the OPV with a blind filter does, in fact, set the maximum pressure as previously said. Of course, this presumes the rest of the machine is within normal build tolerances.

If you send me an email (address below my sig), I will gladly send you the older Bezzera accessories catalog.

OK, so I cleaned the valve well and put it all back together properly (except for OPV setting) and it still didn't solve the problem. Fluctuations still occur during extractions only. The OPV is set to 10 Bar, which is my bad, because I put the teflon tape on and adjusted it too far by hand. You cannot turn the fitting anti-clockwise with teflon tape, because it will unravel the tape. I don't even think you need any tape or sealant there, because there is a bloody o-ring anyway.
Anyway, I think it was a good idea to clean that valve because it did have a bit of scale caked on the part the pushes against the spring, so it may have been sticking sometimes. It sometimes "squealed" indicating it may not have been opening properly at times.
I will order a new pump today.
Thanks for your help Jim and Eric.