Hello everybody,

I'm having a strange problem with my Vibiemme Domobar for a while - the fine gentlemen at German kaffee-netz.de have made several suggestions over the last week, but no solution has come up there yet, so I'd be more than happy if someone here had a good idea. I already disassembled the whole group head, every part looked like new, I cleaned them nonetheless.

Here's a video of what happens - backflow from the OPV can be seen at the left: For the video, I selected an extra coarse grind. You can see the water rushing through during pre-infusion, but then the flow suddenly stops. There is no more pressure on the portafilter, I can just take it out (not shown in the video) and no more water is coming.
Strangely, with a blind basket (correct word?), there's full pressure on the portafilter, no way I can remove it under pressure.

Playing around a bit, I found that there is pressure on the gicleur chamber nut - opening it with the pump running, water comes shooting out there. There is no pressure on the closure plug.


To summarize:
- Lever up, machine starts running
- During pre-infusion, water comes through the portafilter (if I grind coarse enough for demonstration purpose)
- When pre-infusion stops and full operating pressure builds up, there is no more pressure on the portafilter, no more water flows. Pressure still is at the gicleur chamber nut. Every part in between looks like new, nothing is plugged.

I'd appreciate any ideas that can end my coffee withdrawal!

It looks like the pressure ramps and when it hits a certain level, water flows through the opv? Have you changed the opv settings? Does it behave differently with the backflush insert, i.e. with the insert do you see water come out of the opv?