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Rancillio L6 cannot see water level in sight glass

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  • Rancillio L6 cannot see water level in sight glass

    Hello All,

    I used to be on here a few years ago back when I had a Bezerra 2 group. Now I am in another state (WA) and have just acquired a new (well used ...) single group Rancillio L6.

    The machine seems to work ok and is in overall good condition. A few weird things though which lead to a fault. Firstly, I cannot see the water level in the sight glass. This is despite taking water from it via the water tap until it did not want to pass more (1250 ml came out). It does not seem to want to refill the boiler automatically - I guess this is due to the water level probe in the sight glass being in water? I press the blue button and I can hear a valve click (but no pump unlike the Bezerra) and I hear water going to the boiler. The pressure rapidly drops at this time and the boiler heater kicks in. How can there be no water level showing in the glass? Empty?

    Also, the metal probe in the sight tube obviously detects boiler water level. What does the thing with two wires on top of the boiler do?

    I don't think the group is getting all that hot. It is as though either the boiler is full but behaving like it is empty or vice versa?

    I have googled far and wide, and cannot find a wiring diagram or parts list or anything for this machine. Some of the coffee parts places have boiler diagrams etc which look ok but nothing which shows the whole machine as parts.

    I would love to get this machine going and maybe even clean it up, clean out the boiler etc. Any help would be appreciated. Also, if there is anyone in the Perth area who works on these for a living then I may consider having them look it over for me.

    Many Thanks,

  • #2
    The thing with two wires on top of the boiler is most likely a thermal cutout - if the boiler overheats it is supposed to cut the power and stop the machine heating.

    When you can't see the water level in the sight glass, it can either mean the sight glass is completely empty or completely full. Sounds like in your case it is probably completely full.

    The pipe to the bottom of the sight glass can clog up with scale, which prevents the actual boiler level being indicated in the sight glass - what can happen when the level probe is fitted to the sight glass is that the machine fills the boiler but does not stop filling until the level gets high enough that the water suddenly fills the glass via the upper pipe and registers on the probe. If this happens draining water from the boiler via the water tap won't trigger the machine to refill the boiler, as the water in the glass is trapped there by the blockage in the lower pipe, and the probe thinks the boiler is still full. You can test if the autofill is still working by disconnecting the wire from the level probe - after a couple of seconds it should start to fill, and connecting the wire back to the probe should stop it again after a couple of seconds.


    • #3
      Thank you MorganGT and FC for your replies. I heated up the machine tonight and once again was only able to take a litre out of it. This time the level in the sight glass did drop from being completely full to being about 15mm from the full end.

      So, the sight glass was full and this verifies the theory that the bottom of the sight glass end is clogged up with scale.

      Next, I unplugged the unit and removed the wire to the probe. How does the probe work electrically - it runs to a control box down the back of the machine? I then powered up the machine and sure enough the pump ran and water entered the boiler. So, the autofill is good.

      I have now decided that the next item of business is to make photographic notes of the pipework and notes of the wiring and then work on getting the top off the boiler and then determining how to proceed. I expect a full descaling in citric acid will be in order? I will open it up and then post some pics here. Then I will work out what bits I need and get to work fixing it up. I can see the minimum will be new pressure guage (current one does not return to zero), boiler gasket, group seals and screen, plus whatever I need to soak it in.

      Thank you all so much for your considered responses.

      Take Care,


      • #4
        MorganGT - yes, I think the electrical thing on the top of the boiler is a temp cut-out as you said, as it is in the line from the power switch to the heater via the pressurestat.



        • #5
          stripping down L6 and working out what parts are required

          Hello again,

          I tried running some citric acid solution through the unit and got the sight glass to work to some degree. I was not happy so started tearing it down, taking photos and drawing a wiring diagram as I went. The first photo is in the boiler - I estimate about 3mm of scale. Is that bad?

          The second image is of the heat exchanger - it looks like a stalactite from a cave. I suspect I am looking at 24 years of accumulation, as the unit showed no signs of prior disassembly such as knuckle skin and embedded expletives.

          As far as I can see I only need gaskets, new rubber rings, new shower screen etc in order to get the machine working again. Plus, there is the issue of the steam wand valve and the mysterious shiny ball bearing that seemed to appear from within it...

          Also, the outside of the boiler was a shiny metallic colour but the acetic acid has now stripped that back to copper. Is this a problem? It took a lot of soaking to get the crud out of the boiler.

          The element appears to be ok. Is it worth changing these out to avoid a failure down the track or is this not an issue?

          Please bear with me as I run through what I think I need ( I can see these all started as nice round numbers but have changed over time and pressure):

          boiler gasket, 89.3 mm ID, 103 mm OD, 1.6 mm thick made of non-metallic material
          group seal, 60 mm ID, 75 mm OD, 8.4 mm thick
          58mm shower screen (I see no problem with recycling the stainless screw and the brass bit but I think I have seen these as a kit?)
          group to boiler o-ring 5.5 ID, 10 OD, 1.5 thick (in pic 3)
          I next started on the 3 way assembly, and managed to partially strip out the head on one of the 2 philllips head screws holding on the 3 way valve. Is 11mm long and measures 4mm across the threads.
          Next is the 3 way valve, which has three o-rings. One is 28 OD (4th pic) and the two others are 10 OD. It is hard to measure them as they move when I try to measure them but is it that all three of the 10mm o-rings are all the same? They seem the same to me.
          The next image is of the 3way valve body and the plunger bit that moves. Now, which end (the conical rubber or flat) goes towards the brass part with the chrome seat? Inside the plunger thing is a black rubber piece with a conical end that is spring loaded. Now, to me, it seems to catch and not be entirely free, and so could become a failure. Is this rubber bit replaceable or do I have to replace the whole plunger unit?
          The pressure gauge is broken and only ever goes as low as half a bar ...

          The final pic shows the mystery ball bearing. After I pulled the machine down I found the ball just sitting on the frame, where it had evidently rolled out of the valve. I take it that there is supposed to be something that holds the ball in and that I have somehow lost it?

          If you got this far - thank you. I hope to be able to order the parts in one go and get this machine working again.

          Attached Files


          • #6
            The mystery ball bearing acts as an anti-suckback valve to prevent milk being drawn back into the boiler - it seals against the olive on the end of the pipe that attaches to the tap body. When the tap is operating, steam pressure pushes it into the tap, where it stops against a spacer (a short tube, slotted down one side to let steam through). If you remove the tap and tip it up the spacer will fall out too. When it goes back together, the spacer goes in the tap first, then the ball, then you bolt the pipe back on making sure the ball doesn't roll back out!

            I'd just ditch the 3 way valve and fit a whole new one. Individual parts (other than the coil) aren't replaceable. The O-ring between the head and boiler should be an 010 V75 O-ring, same as the ones between the 3 way and the head.
            You shouldn't need to replace the shower screw and the 'brass bit' (water diffuser).
            Don't worry about the change of boiler colour, those boilers are often chromed over the copper but having the chrome come off doesn't affect the operation of the machine.
            If the pressure gauge doesn't zero when disconnected, the needle may have moved on the shaft. You could just buy a new one, but it may be worth carefully opening up the gauge, gently pulling the needle off the shaft and reseating at zero. Sometimes this works and sometimes not (I've done it a fair few times on machines where the original gauge is difficult to source as a replacement part), if it works you've saved the price of a gauge, if not then it won't really be any more broken than it was!