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Odd symptoms and an unusual solution on an E61 Hx machine

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  • Odd symptoms and an unusual solution on an E61 Hx machine

    So I've been having intermittent problems with the rescued ECM Giotto that was the subject of this thread, which is now the winery coffee machine.

    The symptoms:

    On startup it would often splutter and spurt from the vacuum relief or pressure relief on the top of the boiler, leaving a pool of water behind once it heated up.

    It never seemed to call for water to top up the boiler.

    Shot quality was inconsistent, it either flowed too fast or choked, rarely could I hit the sweet spot.

    Sometimes when pulling a shot the boiler pressure would suddenly start climbing from the setpoint (about 100 kPa) to the actuation pressure of the boiler pressure relief, which would, naturally, actuate. If I caught this in time (watching the pressure gauge) I could hold the pressure steady by bleeding water out of the hot water wand or steam wand. Yes, water out of the steam wand.

    The diagnosis:

    Obviously the boiler was overfilling which meant that when it heated up the excess had nowhere to go so it spurted out the pressure relief or vacuum relief.

    At first I thought the boiler level control wasn't coping with the very low conductivity water we have here (TDS around 6), so I added a pinch of salt to the boiler water which brought it up to about 100.

    No dice.

    Eventually I noticed that the pressure climb in a shot was inversely correlated with the flow rate: the lower the flow rate, the more likely it was to go overpressure. My theory now was that the over pressure valve in the pump circuit wasn't functioning correctly, allowing full pump pressure into the grouphead and fill solenoid which was somehow passing so that the boiler was filling during the shot.

    Yesterday I pulled the machine apart and checked the OPV, sure enough it didn't seem to be actuating correctly. I wound the setting ring out a couple of turns and manually moved the plunger by pushing against it with a piece of stainless rod. It moved correctly so I wound the setting ring back in one turn: at some stage I'll check the actual setting with a pressure gauge.

    Next I disconnected the solenoid, connected it up to a 240V source with a switch so I could actuate it, and repeatedly did so whilst feeding it a solution of amidosulphonic acid (the descaling agent from hell) with a pasteur pipette. Once cleaned I rinsed it thoroughly and put everything back together.

    Turned the machine on, checked the pump and everything seemed OK. Ran it as usual this morning: no sputter, pressure at the group seems normal, both my coffees this morning were much closer to the sweet spot than I have been.

    So I guess the moral of the story is that sometimes what seems like one problem is actually a combination of two different problems, which can complicate the troubleshooting process.
    Last edited by Lyrebird; 8 April 2019, 02:43 PM.