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EM6910 pressure 'surging' or 'pulsing'

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  • EM6910 pressure 'surging' or 'pulsing'

    Hi guys.

    i have a em6910 that has started behaving a bit oddly lately. its about 2 years old, maybe more and has been a great machine so far. does what i need it to do. i went away on holidays for 4 weeks, and since coming back its just not been the same. clearly it didn't like sitting idle for that length of time. the first time using it after the break, the pump sounded quite metallic, similar to when its first bought and you need to purge a lot of water through it. it did improve in sound quite quickly, but the issue i have, is ever since my 4 week break, the pressure isn't consistant. the guage, which i know is just a guide, builds pressure as per normal, but once the pour starts, it tends to fluctuate a good 5mm or so, and the pump is clearly 'surging'.

    i have descaled it with sunbeam tablet as per instructions, chemical back flushed it, cleaned both shower screens etc etc but it hasn't made any difference. i normally backflush with water after every shot as well. i'm pretty good with the maintenance, which is why i think it has something to do with sitting idle for 4 weeks.

    the pour still looks ok, the coffee tastes ok and the pucks come out in one piece, although there is a small amount of residue compared with before. previously the basket would be clean enough to hardly need wiping even.

    any ideas as to what could be the possible issue?

    also the volumetrics seem to be a bit off. the book says it should automatically stop (when descaling etc) after 250ml but mine pours at least 350-400ml before stopping.

  • #2
    Mine does that when the machine chokes. It doesn't have an OPV so the pump maxes out and has that sudden drop in pressure which then builds back up etc, etc. I find that mine stabilises after a few surges and is good for the rest of the pour.

    Check your beans and grind first and play around with them, coarsen it up a bit and see what happens. If you're using the same beans that you had before the 4 week break then the grind will need to be adjusted to accommodate for the age of the bean.


    • #3
      Pretty sure it's not a technique issue. I'm a believer in beans only lasting up to 4 weeks so buy fresh beans twice a month (Merlo).
      I've persevered with it for a few months now and it's not improving but thankfully not getting a lot worse either.

      Once upon a time it would have been a good excuse to upgrade but can't afford it at the moment.
      Last edited by prydey; 17 July 2014, 06:57 AM.


      • #4
        I used to see that issue with mine when the pump gets air in it.

        I used to "burp" the system as follows
        -fill the reservoir as physically full as you can without overflowing,
        -crack the steam tap and water tap far enough that it opens the valve but doesn't turn on the pumps
        -then turn on the machine
        as it heats up it allows the air to move up the pipes easily,.
        -once hot, run the hot water until it's a consistent flow and you should be good to go.


        • #5
          Are you talking about this?

          I might just try your trick and see what it does.


          • #6
            It did bubble stuff out but still not go. Have a feeling there is a leak somewhere.