Possible OPV (?) problem in Bezzera BZ07

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the-hexx
Posts: 2
Joined: 5 months ago

#1: Post by the-hexx »

Hi Everyone,

This is my first question in this forum, and as a non-expert, my terminology may be a bit off, so please excuse me.

I recently received an old (about 10 years old) Bezzera bz07 from my brother, which replaced my Rancilio Silvia

While my Silvia served me well, I find that the Bezzera gives better and more consistent results, and also easier to maintain.

However, I noticed from the first day that the pressure indicator is always set to 0 bars, even when brewing coffee. I kinda got along since I didn't have OPV or any indicator on the Silvia either.

Today I tried to backflush the machine with blind filter and cleaning powder. Suddenly the pressure raised on the indicator (reaching almost 12). Also, I assumed the water pushing in will be released through the valve in the bottom after each cycle, but it didn't. When taking out the portafilter there was a significant release of pressure. This was even worse when trying to cleanup (doing the same cycle without the cleaning powder). Pressure built up very fast and the machine started making weird noises. Again, no water came out from the valve below.

Notice that the valve below the indicator (not sure what the proper term is) Sometimes drips some water while operating the machine, but I was assuming it should spit out a lot of water during backflushing (which it didn't), similar to how water "backflushed" on the Silvia.

Can you maybe explain if there is indeed an issue and how can I fix it. I want to be able to regularly backflush the machine. Also, having a proper pressure indicator would be nice. Other than those issues the machine is in great shape, so it is worth the effort!

Attached is an image of the indicator when machine is running (always on 0) and the valve below.


Thanks!

Nick

DeGaulle
Posts: 544
Joined: 10 years ago

#2: Post by DeGaulle »

The valve that releases the pressure into the drip tray at the end of each extraction or each backflush cycle is the solenoid valve (not the OPV). Your observation during backflushing suggests that it is defect or blocked. What I find strange though is that the pressure has been sitting at 0 at each extraction until you started backflushing. There may have been something clogging the pulse line of the pressure gauge, which may have been cleared by the cleaning agent.
If you're the DIY type, open up the cover and remove the solenoid that sits just above where the pressure gauge is mounted. If I'm not mistaken, if the coil is de-energized, a spring should push the plunger to closing the water inlet port and opening the exhaust port. It may be obstructed by fouling (scale?) or the spring may have failed.
Bert
★ Helpful

the-hexx (original poster)
Posts: 2
Joined: 5 months ago

#3: Post by the-hexx (original poster) »

Thanks, I will try that