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Thread: Brew pressure gauge creeping up.

  1. #1
    SPH
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    Brew pressure gauge creeping up.

    Wondering if the pump in my boema is faulty. When I turn the water on my gauge flicks up to 4 bar and sits there rock solid. When I pull a shot the pressure shoots up to 9 bar for the duration of the shot. When the pump is switched off the pressure doesn't drop back to 4. It sits at about 7.5 and creeps up from there.

    I've tried three limiting valves including and adjustable. I've tested all three with a RMC pressure tester and they're all working.

    I'm wondering if the pressure is building up on the machine side. I don't know if there's a non return valve in the machine anywhere.

    Bit of an odd one. I don't have any real espresso machine experience so I don't know if it's a common issue or not.

    Any help appreciated.

  2. #2
    Senior Member sprezzatura's Avatar
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    Have a look at the expansion valve. It may need replacing as it doesn't sound like the HX circuit is releasing pressure. Oh. And Bo-Ema gauges. Are all over the place.

  3. #3
    SPH
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    Pardon my ignorance but where does that valve live?
    I'm at the machine now. It's behaving its self at the moment. I cranked the adjustable pressure gauge way down. Idle pressure is about 175kpa. I'll need to adjust the pump pressure up if it needs to stay that low.

  4. #4
    Senior Member sprezzatura's Avatar
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    I've actually got a Bo-Ema on my bench so you're in luck. I'll post an image when I get home.

  5. #5
    Senior Member sprezzatura's Avatar
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    Here's the OPV
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  6. #6
    SPH
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    Ahh, that little guy. I thought that pretty much had to be it. Thanks. I'll check it out next time I'm standing in front of it.
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  7. #7
    Senior Member sprezzatura's Avatar
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    And here's your vane pump bypass

    This girl is old. I'm doing a couple things on it and it's going back to the milk bar where it probably does 500g of rancid coffee a week.

  8. #8
    SPH
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    That machine looks to be in much the same condition as mine was before I ripped into it.
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  9. #9
    SPH
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    Thanks again! I had adjusted the pump pressure down when I had it on the bench. I only had a 500kpa limiting valve on hand so by the time the pump boosted it the pressure was running a bit high. Now that the pressures lower I'll adjust it back up.
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  10. #10
    Senior Member sprezzatura's Avatar
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    Brew pressure gauge creeping up.

    Quote Originally Posted by SPH View Post
    That machine looks to be in much the same condition as mine was before I ripped into it.
    So the pump gauge on this girl sits at 8 bar but I have a 350kpa pressure reducer and a BWT Remin filter. When I pull a shot the pump gauge reads 12 bar and goes back to 8.

    Here's a trick to test your pump: buy a gauge (preferably big and oil-filled) and fit it to a 3/8" braided mains water line. Using a 20mm spanner remove the outlet hose and attach your home-made pressure gauge. If you want get elaborate t in a T and run the gauge off the T out of the machine. Hold it in your hand and pull a shot.

    You can try a portafilter gauge but those thin Bo-Ema group seals usually blow out.

  11. #11
    Senior Member sprezzatura's Avatar
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    Heck, I'll try this after lunch. I'll post some images.

  12. #12
    SPH
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    That idle pressure seems pretty high. My gauge (which is only about a month old) reads 8-9 bar when I pull a shot and drops back to 3 at idle. Which is about right, 3 bar being 300kpa.
    At least that's what it reads when it's behaving its self.
    The RMC test gauge is just what you were describing.

  13. #13
    SPH
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    This machine is in a shop where they say things like "tastes petty good for Coles beans, eh?" And the operator says "I've been a barista for 15 years, I need to get the manual so I can adjust the shot timer. It's running for far too long". Didn't want to hear about 'volumetric' or 'adjust your grind'. This is the only machine I've ever worked on and I already know more about pulling a shoot than these (well meaning) doofuses.

  14. #14
    Senior Member sprezzatura's Avatar
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    Quote Originally Posted by SPH View Post
    This machine is in a shop where they say things like "tastes petty good for Coles beans, eh?" And the operator says "I've been a barista for 15 years, I need to get the manual so I can adjust the shot timer. It's running for far too long". Didn't want to hear about 'volumetric' or 'adjust your grind'. This is the only machine I've ever worked on and I already know more about pulling a shoot than these (well meaning) doofuses.
    Ah yes. Old school. Make you a good roadhouse cappuccino on the same steam wand they make onion gravy with.
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  15. #15
    SPH
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    Har, onion gravy.

  16. #16
    Senior Member sprezzatura's Avatar
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    Brew pressure gauge creeping up.

    Quote Originally Posted by SPH View Post
    Har, onion gravy.
    No lie. Saw it with my unbelieving eyes.
    Last edited by sprezzatura; 1 Week Ago at 07:52 PM.

  17. #17
    SPH
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    Heat your canned soup with the soup wand and make cuppa' soups with the soup heads. Just load up the soup handle and flick the switch. It'll even filter out the lumps!

  18. #18
    Senior Member sprezzatura's Avatar
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    So here's a montage of the rebuilt OPV and bypassed water pressure gauge.


  19. #19
    Senior Member sprezzatura's Avatar
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    Obviously the machine's water pressure gauge is cactus.

  20. #20
    SPH
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    Hard to argue with that. 350.

  21. #21
    Senior Member sprezzatura's Avatar
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    Even a bit less due to the looong braided 3/8" hose robbing a bit of pressure.

  22. #22
    Senior Member sprezzatura's Avatar
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    This machine doesn't like to bleed pressure off after the solenoid exhaust dumps post shot. It slooooowly backs down. I wouldn't worry about that much.

  23. #23
    SPH
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    Yeah. When mines playing up the pressure slowly builds up.

  24. #24
    Senior Member matth3wh's Avatar
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    Where can I get some of this skim double shot gravy to go with my Rosie's chicken?
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  25. #25
    Senior Member sprezzatura's Avatar
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    The same place that makes poached eggs out of the tea tap water.
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  26. #26
    SPH
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    Ohhh, I didn't even think of that! Geez. Talk about living in the dark!

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