Pygmalion DavecUK: if it is due to some air somewhere in the system, do you think it would be possible to bleed it out somehow?

Probably not and with coffee in I am surprised the effect was as sustained as it was unless the coffee was quite a tight grind. Also when I say air and water hammer, I would expect the effect to be very transient. Air itself compresses to feck all at 9 or 10 bar….which would cause the hammer and can be fairly quickl;y absorbed at those pressures..

In your first video, what happens if you repeat the experiment, but fill the blank portafilter basked with cold water and carefully lock it into the group, spilling as little as possible.

Otherwise I’m mostly out of ideas.

  • could it be a sticky expansion valve (I don’t think so), unless there is a manufacturing defect? But it still doesn’t explain why after a shot or two the problem always goes away.
  • Some weird water heating expansion effect (but that doesn’t fit with the way the Hydraulics are connected.
  • Some fault on the gauge but then why does it self correct after a few shots?

Nope I’m a little stumped. We can eliminate heat effects, if someone wants to disconnect the brew boiler heating elements, turn the steam boiler off then repeat the blind basket experiments.

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    Pygmalion Here is a simple experiment you could try.

    Done!

    The temperature was at 96C because it was on at the end of the heat up cycle towards 93C. For the sake of the experiment, on the subsequent shot, I have set the temp to 96C, let it get here and set it back to 93C.

    On the subsequent shot, I emptied the blind basket before starting, so both are from the same starting point. They were taken approx. 7 minutes apart. I also did one with the basket full of water, and the behaviour is the same overall, with the exception that, as expected, it reaches the target pressure faster.

    When using coffee rather than the blind basket, the behaviour is the same, but the pressure gradually goes down to approx. 8.75 bar on the dial over the course of 35 seconds, as expected.

    From cold:

    7 minutes later:

    This is an older video where it shows a coffee pour. This was when the Elizabeth’s pressure was set at 10 bar. But you can see the behaviour of the gradual pressure reduction. These days is the same, but at 9 bar or thereabouts.

    With coffee (older video):

    Hope the above is helpful.

      I pulled a shot with no PI, it went to 11 bar then gradually decreased to approximately 9.5 until the end of the shot. I filled the blind basket to the brim with cold water and hit button 1 again (no PI), it went up to 11 bar and stayed there until I stopped the shot. Is it that the opv is tuned to 11 bar (in my case here) and simply reduces as the puck gets extracted? I don’t see an issue really or is this different to the OP’s issue? I had noticed this recently but didn’t worry, as the coffee still tasting great

        JahLaza pulled a shot with no PI, it went to 11 bar then gradually decreased to approximately 9.5 until the end of the shot. I filled the blind basket to the brim with cold water and hit button 1 again (no PI), it went up to 11 bar and stayed there until I stopped the shot. Is it that the opv is tuned to 11 bar (in my case here) and simply reduces as the puck gets extracted?

        If this is the consistent behaviour, it could indeed be that your expansion valve pressure needs reducing, try reducing it to 9.5 bar against a blind filter and see how you get on.

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          JahLaza - what you are describing is absolutely normal and it is what you see on my videos, albeit at a lower pressure.

          It’s not, however, what @Del_UK and Pygmalion are experiencing.

              Yeah, ok, thanks both. I wonder if there’s any need to reduce it at all? I had read somewhere the difference between 9 and 10 bar isn’t worth talking about would you advise to reduce it a bar or so in my case?

                JahLaza would you advise to reduce it a bar or so in my case?

                Try it, it’s very easy. Only your taste buds will tell. 😊

                  Thanks for running the experiment, @MediumRoastSteam ! Glad yours is working normally.

                  I tried the experiment with the blind basket initially full of water, and the behavior was still there with no notable change except for attaining pressure sooner, as expected.

                  I have opened a ticket both with my reseller and Lelit directly, to see if they can assist. But in the meantime, if anyone else has any theories I’d love to hear them.

                    Reduced it to 9.5bar with blind filter (yes it was a very easy action!) just pulled a shot, it still went up to 10.5 bar at start of shot but maintained about 9.5 bar from about 13 secs. Tastes great, not sure if there’s a difference, fuller body I think maybe. Apologies if I’ve slightly diverged from the thread topic folks, interesting all the same🤔

                    Pygmalion I think I have the same issue as yourself. When I run first cycle with blind basket it hits 11 bar before slowly falling down towards 9.

                    Subsequent cycles go straight to 9 and hold. I tried filling the basket with cold water and that one goes straight to 9 bar and holds there.

                    I will pay attention to tomorrow mornings shots to see what is happening with coffee in the basket. I never look at the needle - watch start of shot then fill my milk jug whilst it’s pouring.

                    Niche Zero

                    Niche Zero

                      @MediumRoastSteam I use self-made remineralized water. It is 70/30 water: distilled water with a tiny bit of baking soda and Epsom salts added according to the recipe here:
                      https://s3-ap-southeast-2.amazonaws.com/hosted.fivesenses.com.au/hosted_docs/water_recipe.pdf

                      Interesting results, @Ando . It seems like your behaves normally when the blind basket initially contains water, though, while mine didn’t behave any differently in that scenario.

                      • Ando replied to this.

                        Pygmalion If I leave my machine for a while, fill blind basket with cold water - it overshoots to between 10 - 11 and slowly drops from there.

                        Everything following this first one goes straight to 9 and stays there.

                        If this is normal then grand. But it does seem very similar to what your videos were showing

                        Niche Zero

                        Niche Zero

                          Ah, I see @Ando - I misunderstood. Sounds like yours is behaving similar to mine then.

                          I also am ok with all this if it is normal and isn’t affecting the coffee. But, it doesn’t sound like it is especially normal, given that at least @MediumRoastSteam’s machine doesn’t seem to do this. I also worry that, since it definitely does this for me with coffee too, my initial shot of the day will end up being significantly different than subsequent shots, given that it will be at notably higher pressure than the others. Also, if it is indicative of some sort of flaw in the machine, then that just means a potentially more likely failure down the road, which I’d like to fix now while under warranty.

                          Curiosity got the better of me and turned machine back on to pull couple of shots with coffee.

                          First one touches 10.5 bar when machine ramps up (no PI) and is just under 9 at the end of the shot.

                          Second shot made straight after only goes to 9 before beginning to drop down to 8 by end of shot. This was 2 secs slower than first one.

                          So consistent with what was happening with blind basket tests.

                          Something to be concerned about?

                          I do struggle to dial in a lot of the time and get consistent shots that take same time etc.. I always just put it down to my inexperience or some other reason however …

                          Niche Zero

                          Niche Zero

                          After reducing opv to give 9.5 bar in blind basket yesterday, I pulled first shot this morning, it went up just past 11 bar and then back to 9.5/10 bar during shot. I adjusted the opv again to give 9.5 bar using blind basket. Pulled a shot of coffee it shot to 10 bar then finished out around 9/just over 9 bar. Could it be these OPVs loose their adjustment? I’m no authority on them but looks like something like that maybe in this case? Not hugely upset the coffee is great but as others have stated if there’s a defect/sign of defect it’s still in warranty!

                            JahLaza When the machine is cold and unplugged. Take pipe off expansion valve, and split expansion valve by undoing it as if you are lowering the pressure… note how many turns. Don’t remove the expansion valve from the machine.

                            Remove bits inside in order….so you know how they go back. Then photograph (best quality you can), post photo here. Photo both sides of the pad bit.

                            If it’s a bit like this photo, lubricate the metal part of the disk with the rubber pad, and of course the top o ring before replacement, tighten up the same number of turns, then check the pressure.

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                              Should get to it later today what lube would you suggest (I don’t have any molycoate or similar I can pick something up today)?

                              Plumbers silicone grease…as this is only a test, one I can’t actually do. Molykote 111 would be the ideal.

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                              @DavecUK Couldn’t get any molykote but got some silicone grease. Before I open it, is it at these 2 points I should lubricate?