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Thread: noise when pumping without coffee. normal?

  1. #1
    Senior Member
    Join Date
    May 2008
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    600

    noise when pumping without coffee. normal?

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    Hi,

    I have been restoring a Rancilio 2 group S20 midi DE. *All is going well - completely stripped it, cleaned and descaled, replaced all the seals and gaskets, and put it back together. *Just made my best coffee in years (actually, ever!) on it, so it was worth the effort! *I had been doing the same roast for a good year or so, so I was very surprised to see how different it tasted on another machine.

    I only have one noise I am not sure should be there. *I think it is coming from the gicar flowmeters (yes, a separate noise from each group when that group is activated). *I get the noise only when I pump without coffee in the filter. *when coffee in in there I dont get the noise. *when I put in a blind filter, I hear it for about .5 seconds, then it stops. *Im pretty sure there are no leaks, and dont think it is an ovp. *it still makes then noise when I run the machine cold. The noise is hard to describe, the best I could do is say it sounds like pressurised water being squirted (pressure set to 9.5 bar).

    I noticed when I had the flowmeters out for cleaning that there is a very small entry hole into the meter. *My theory is that this is the point of most resistance in the hx/thermosyphen/group line from the pump, and this results in the pressurised water making a bit of noise through this point when there is no coffee. Does that sound possible or am I looking at another problem?

    Any help would be great. *

    Thanks, Damian. *



  2. #2
    Senior Member
    Join Date
    Jul 2006
    Posts
    3,498

    Re: noise when pumping without coffee. normal?

    Damian,

    I think your reasoning is spot on.

    On my La Cimbali there are two flow restrictors (one for each group). These provide a slow ramp up of pressure to provide pre-infusion. With a puck or blind filter you hear the water rushing through the 0.8mm hole for maybe a second - until the pressure in the PF starts to build.....

    But if the group is left open.... then the "venturi" noise continues as the water pressure drops from 9 bar to zero across this 0.8mm hole......

    Not familiar with the Rancilio...... but wouldnt surprise me if it does something simlar.

  3. #3
    Senior Member
    Join Date
    May 2008
    Posts
    600

    Re: noise when pumping without coffee. normal?

    Hi, thanks for the quick response! It would be great if htis was a normal noise - I dont think I have it in me to pull it apart again!!!



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