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Whats happening with my Expobar minore 4? or Why is my vibration pump humming?!?

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  • Whats happening with my Expobar minore 4? or Why is my vibration pump humming?!?

    This is a vibration pump model
    Every once and a while when pulling a shot the machine ramps up to 10.2 bar ( which I have set it to at the OPV) then the pump seams to go to an almost silent hum and the pressure drops back to about 9.5 bar, to me it sounds like the pump is not pushing like it normally does,

    Usually the pump stays at an even tone pumping hard at around 10ish bar till I stop the shot

    I have worked out it seams to mainly happen when the machine has been on for quite a few hours

    When it happens I run a few shots with the blind filter and it still does it so I will shut it down and let it cool

    Could it be something to do with heat, possibly something is getting to hot

    Hopefully someone out there can help me

    I did mention it at my last service but did not get an straight answer, just got told the pumps fine and they could see no problem,

    But as I said it just happens randomly so who knows!

    Thanks
    Last edited by Javaphile; 13 November 2012, 08:48 AM. Reason: Fulfilling requested title change

  • #2
    Ok today I have pulled around 8 shots all ramping up to 10.2 bar then the pump tone goes to a near silent hum and the brew pressure drops back to 8 bar and sits there till I finish the shot,

    This is the first time it has happened every time a pull a shot,

    Also notice the brew pressure guage is slowly fluctuating when idle rising up as far as 8 bar

    Any ideas ?

    Possibly a new pump ?
    Last edited by NakiChap; 11 November 2012, 09:07 PM.

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    • #3
      Tonight I pulled the OPV valve apart seamed to be clean put it back together ran a couple of blind shots and all ok,
      I read on HB a chap had a similar problem with the pump going to a humming and losing pressure and it was caused by the water getting to warm in the tank,seams that some pumps are only rated to a certain water temp,
      My machine only seams to develop this problem after being on for a number of hours so when it happens again I will empty the tank refill with cold water and see if that stops the problem,
      Still think it is something with the pump because it seams to go from vibrating to a humming.
      Will see how we go over the next week.

      Comment


      • #4
        I've read your postings with interest as I have a Minore IV just over 2 years old. I haven't noticed this problem to date. How old is your machine?
        Your idea of warmer water in the tank contributing to this is interesting.
        I do not normally have my machine "on" for more than a couple of hours at a time, but with the warmer weather, the location in the kitchen and heat generated by the machine when left on, could play a role in your "problem".
        After all, these are mainly a home machine, but when used in a semi-commercial situation, the water usage/turnover would maintain a constant tank temperature.
        You could always try a handful of filtered ice cubes in the tank instead of changing the water if you find that changing the water stops the "humming".
        As an experiment and to assist you in solving any potential issue, I will leave mine on for an extended time today and test the theory.
        Look forward to your updates.

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        • #5
          Ok seams this is only happening when the water in the tank gets warm
          Refill the tank with fresh cold water problem goes away untill the water again heats up
          spoke to an expobar tech and he has never heard of this problem but he does think pump issue
          Will purchase a new pump and fit it untill then will keep running cool water.

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          • #6
            I have a vibemme domobar super and believe I have also experienced the symptoms of which you describe. I have the model which doesn't have the brew pressure gauge, so have been unaware of the potentially associated pressure drop. I'll try over the next week or so to see if I can replicate and dispel by changing the temp of the water. I had always assumed that it was usually due to perhaps an overly tight extraction. Either way, without the gauge, it's never been an issue for me and I don't see it becoming one now. I don't think I could taste the difference, but for curiosity sake it might be interesting.

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            • #7
              My machine is only 18 months old

              If you search Vibration pump humming on Home barrister there is a number of threads regarding this issue

              Just wish I had worked this out before the warranty was up

              Wondering can the mods change the heading of this thread to " vibration pump humming "

              Would make it easier for anybody else with the same issue to find.

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              • #8
                every expobar i have used does this when extracting to fine, pump pressure rises until opv limit, at which the pump goes into restart cycle(drops pressure completely and restarts)
                it should sound no different to pausing an extraction and then restarting it asap.
                if it sounds heaps worse then you may have a problem, if the vibrating is the same then you should be sweet.
                i find this happened to my expobar office when using a la mazorocco portafilter with a 21gram basket and did a slow extraction

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                • #9
                  Originally posted by D4MMO View Post
                  every expobar i have used does this when extracting to fine, pump pressure rises until opv limit, at which the pump goes into restart cycle(drops pressure completely and restarts)
                  it should sound no different to pausing an extraction and then restarting it asap.
                  if it sounds heaps worse then you may have a problem, if the vibrating is the same then you should be sweet.
                  i find this happened to my expobar office when using a la mazorocco portafilter with a 21gram basket and did a slow extraction
                  Hi D4MMO what your describing has happened to me before where the pump drops pressure completely then ramps straight back up again,i thought it was the boiler wanting water during a shot,anyway my problem is different the vibration stops and becomes a humm,

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                  • #10
                    I have the same machine and recently noticed that while pulling a shot, the pressure would suddenly drop and ramp up again.
                    I suspect that it might be due to channelling, allowing for a quick lost of pressure, but not sure

                    however I dont have the problem that you mentioned, about the humming

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                    • #11
                      Originally posted by Joyo View Post
                      I have the same machine and recently noticed that while pulling a shot, the pressure would suddenly drop and ramp up again.
                      I suspect that it might be due to channelling, allowing for a quick lost of pressure, but not sure

                      however I dont have the problem that you mentioned, about the humming
                      Hi Joyo,
                      I dont think channeling is causing the sudden drop in pressure,I do know what you mean though as my machine also does this at times ,D4MMO called it a restart cycle ? in his previous post

                      Getting back to my original problem, if the machine has been sitting idle and the water in the tank is fairly warm I just empty it out refill with fresh cold water before pulling a shot and I have no problems, no humming pump,
                      So cold water no problems ,tank water gets to warm my pump does its humming thing,

                      I have purchased a spare pump from coffeeparts but will not change it yet because as long as I have cold or cool water running through my pump there is no problems,

                      Has anybody else come across this problem I recently spoke to another CS member with a minore and his machine also did the humming .

                      Thanks javaphile for editing the heading cheers

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                      • #12
                        Fix

                        I had the same problem this morning. Water in the tank was cold, so i gave it a really good back flush with and without cleaner. Fixed the problem for me.

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                        • #13
                          Had a similar issue with mine recently, Minore 3.
                          I went searching and pulled the pump out to replace it with a loaner that works. Not the motor that was the problem.
                          Mine turned out to be the water pressure valve (OPV) spring. The spring had compressed to the point it couldn't be wound in anymore. Easy fix with a new spring or to stretch the current spring so the adjustment screw will not bottom out. Hardest part was getting the circlip out.

                          Be careful, anything electrical should be done by or with a qualified person.

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                          • #14
                            Alright, Friday housekeeping and I'm going to detail my fixes over the years. I've owned an Expobar Minore 4 for nearly a decade I think and they're really good, but spoiler alert. They break.
                            In relation to this particular issue, the issue where it will be pulling the shot fine and then drop all/most pressure and hum very faintly, usually when it's warm and the issue generally doesn't present whilst dead cold.

                            Swapping out the water pump fixed it 100%. I previously tried the other steps listed and others to no avail.

                            https://www.jetblackespresso.com.au/...ibration-pump/ I believe it was. It was the exact same as I pulled out of my machine anyway.

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