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Rancilio Silvia pump losing prime when hot

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  • Rancilio Silvia pump losing prime when hot

    My Rancilio Silvia is about 16 mths old. Recently it's been playing up when hot. The pump refuses to prime and no water comes out of either the group head or the steam/water nozzle with either the brew or water switches on. All that comes out of either outlet is steam (but much less than when steaming milk). The pump runs, but doesn't sound like it's working, i.e., there's no load on the pump. The pump primes properly when cold. I go through the boiler filling routine each day, as I empty the water hopper when I'm finished using the machine. The pump works fine doing this. The problem has been there for a while, but seems to be becoming more frequent. When I first got the machine I could let it sit all day without a problem. I can avoid the problem by running the pump for a short while every half hour our so. It's as though the pump is heating and the water is vapourising causing it to stop pumping but this seems unlikely in a plastic bodied pump. I don't think that it's drawing air through the suction as there are no leaks there, i.e., no water collecting under the machine. I'm mystified as to what's going on. Could it be the seals in the pump failing once they heat up? Sometimes the pump will eventually start pumping after running it for a while. At other times it just won't start pumping and I have to switch the machine off for a short while.

    I do a weekly backflush and have wondered whether this can be detrimental to the pump. The manual recommends this and I wouldn't have thought it would be detrimental as the pumps are rated at 15 Bar and the OPV shouldn't let it get to this pressure. I recently fitted an Auber PID kit. The problem has become more frequent since fitting the kit, but it was the problem started well before doing this, so I don't think that this would have any bearing on the problem.

    Does anyone have a clue as to what's going on? What's the construction of the pump, is it a diaphragm pump?



  • #2
    Have you ever de-scaled, if so, when was the last time?


    • #3
      No I haven't de-scaled as yet. I'm in Melbourne and was told that de-scaling was only required every two years.


      • #4
        Depends where you live, your water. It won't hurt to do it, only help.


        • #5
          I have a Silvia too with auber pid, 13 months old, I've descaled twice so far, prob only needed it once. 16 months if you haven't done it, do it.


          • #6
            Thanks for the responses Delish007. We don't get a lot of scale build-up here in the Eastern suburbs of Melbourne, the water is not very hard. Our kettle is about 8 years old and doesn't show much beyond a bit of discolouration. I might give descaling a go, but I don't think that this would be causing this problem. The pump runs but it sounds like its full of vapour, it's quieter than when it's pumping water. I'm sure that temperature has something to do with it.


            • #7
              Mark, wondering if you got your pump issues sorted? Was searching for suggestions on cleaning solutions for back flushing the Silvia and came across this. I just picked up a 2nd hand Silvia and had to prime the pump to get going, you didn't mention if you actually tried priming the machine.

              The process is simple:
              - fill water tank
              - with machine off, fully open the steam valve (counter clockwise)
              - turn on the espresso switch, then turn on the power
              - close the steam valve (clockwise) as soon as water comes out of the steam wand
              - water will now flow from the group, allow at least 500ml to flow through

              After doing this i still noticed some air pockets in the water pipe and was able to bleed that without much hassle.

              If you haven't tried this yet it will probably do the trick.


              • #8
                Hi OG2shots, I do go through this process every time I start up the machine and it primes when it's cold. It just has trouble priming using the same process, once it's hot. I've just this weekend replaced the pump because another problem made me think that the pump seals might be failing. I've still to find out whether the priming problem has been fixed by replacing the pump. The new problem was a drop in the volume of coffee delivered. This hasn't been fixed by the replacement pump, and I suspect that the OPV valve might be causing this latest problem.