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VBM 3-way valve leak

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  • VBM 3-way valve leak

    Hi guys,

    I've got a VBM Domobar Super and recently I've noticed that the 3-way valve has been leaking water (while idle), which then causes the pump to kick in - presumably to refill the boiler. At times it will just stop leaking and everything will be back to normal up until I make my next coffee.

    I enjoy fixing things, taking things apart and putting it back together, but before I begin taking her apart, are there any suggestions on what might be wrong, what I should test/look out for/purchase/replace? (as well as where I would get such parts).

    - cj

  • #2
    Yes chunjun,

    If a good backflush doesn't cure it, the problem will often be perished seals in the the group pistons. Alternately the cam followers on the end of the pistons may be worn.

    If I see wear, I tend to replace the pistons as a set. If not, the seals are these ones. Beware though as many a cam follower snaps off the piston when trying to do the seals- so you want to have a spare just in case. Here's the schematic.

    Coffeeparts sells the bits or alternately your local ECA service agent will probably have the parts and/or can do the job for you.



    • #3
      Thanks for info and links Chris! I'm going to order in some parts from coffeeparts, might as well keep some spares handy. Seeing as I've never gone any further than taking off the mushroom, have you got any tips that might help me avoid any damage to the chrome while disassembling it?

      - cj


      • #4
        Originally posted by chunjun View Post
        the 3-way valve has been leaking water (while idle), which then causes the pump to kick in - presumably to refill the boiler
        This I think warrants some further investigation before you buy the parts - water leaking from the group of a Domobar Super should NOT have any effect on boiler water level. If the two symptoms (leaking from group and occasional auto-filling) are related, then there's water getting from the boiler into the HX, which is a bigger issue.

        I think it's more likely that you have two small problems in a leaky 3-way and a small steam leak, but it would be good to attempt to diagnose this further.


        • #5
          Actually now that you mention it, I didn't think much of it but more often than not I only see steam when I first pull the brew lever up, and it takes some time (anywhere between 5-10 seconds) before any water actually comes through the group head.


          • #6
            that's OK, to be expected if the group valve is leaking - pressure in the HX is normally very high and the water in there can't reach boiling point, but as soon as the pressure drops (from water loss through the group) the thermosyphon stops working, and the water in the HX flashes to steam.

            Can you shed any more light as to whether the autofill kicking in is related to the leak?


            • #7
              What I've observed is that the 3-way keeps dripping/dribbling, and eventually the pump kicks in. Water continues to leak, and after a short while (anywhere between 30-90 seconds) the pump kicks in again. This just continues on until I have to empty the drip tray. If I pull the brew lever, the 3-way stops leaking and the water is redirected to the group head. It builds up pressure at the group head just fine and I can still make coffee. At times the leak just stops altogether and I can actually walk away without worrying that the drip tray will overflow.

              Also, drips can come out of the steam wand and hot water spout as well although I'm not sure why since they're both shut.


              • #8
                So we can definitely say the top e61 valve seal (accessed via the group mushroom) is gone - this is the only route for water to leak out of the HX. I'm still at a loss to explain why the machine is auto filling though, this would imply that you're losing water out of the boiler as it leaks from the group (cracked heat exchanger) but this is very unlikely and you'd have serious issues from the boiler overfilling when you made coffee if this was happening. I'd start with the E61 valves (top one at least, but might as well do both) and see what happens to the autofill.

                Steam and water wand seals can be replaced as well, the VBM ones are quite soft and can drip a bit when the pressurestat kicks in.


                • #9
                  Replaced the entire brew valve as well as the infusion valve, so far so good. Thanks for the advice Rick and Chris!