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Thread: Help needed with Grimac Mia temp

  1. #1
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    Help needed with Grimac Mia temp

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    HI All. Just picked up a used Grimac Mia. Using my multimeter and bead thermocouple, I can only reach 188 F, and that's with the bar set at I think a really high 1.5. I can't even get the water to splutter and steam out of the group. Any ideas, thoughts?

  2. #2
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    Could be a leak from boiler (heating element seal most likely) or faulty heating element or pressure stat.

    Could also be false pressure (try letting off steam when warming up) or that the anti vac is not closing and allowing enough pressure to build (is there a constant hissing/steam sound).

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    Hi Ben. There does seem to be some sign of a leak on top of the boiler, maybe. It's not wet at all just some residue scale looking deposit. There is no constant sound and I don't know what an anti-vac is. I'm going to have a bit of a look to see if there is scale build up. Apart from that I have no idea what I'm doing. Just upgrading from my Silvia V3. There are no local decent service agents so hoping to problem solve myself. Thanks for you time.

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    Here is a parts diagram which should help you know the internals better;
    https://coffeesnobs.com.au/documenta...er-models.html

    The anti vacuum valve is a valve on top of the boiler which vents steam as the pressure builds then seals up to allow full pressure to be set by the pressure stat. It has a small tip about 1cm long which sticks out when up to pressure. You can test it by carefully pressing with a wooden spoon (be careful as it will vent boiling hot steam). If there is some scale on top of the boiler there is a good chance it is stuck or faulty, you can also remove, pull apart, clean and soak in descaling or cafetto cleaner to see if that gets it working.

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    boiler.jpg
    This is a pic of the top of the boiler. There appears to be a small hole where the build up is. Is this the anti vac valve?

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    boiler bottom.jpgIt's ok Ben. Have found that 1cm anti-vac. Seems to be working well. Any idea about the hole with the residue?
    Also, here is a pic of the underside of the boiler. I assume that's the heating element. Doesn't look too good.
    Last edited by Burkeyboy; 3 Weeks Ago at 04:58 PM.

  7. #7
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    Quote Originally Posted by Burkeyboy View Post
    boiler.jpg
    This is a pic of the top of the boiler. There appears to be a small hole where the build up is. Is this the anti vac valve?
    Anti-vac valve is in the bottom right corner partly covered by the pipe.

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    Those pictures are very nasty and the boiler & heating element are in rough shape, along with all the items on top of the boiler look in poor condition.

    1) Pic 1 - If that is a physical hole in the top of the boiler then it could be terminal or require a professional repair by a boilermaker. With this hole the pressure will never build up as it is meant to be a closed system. If not repaired professionally and pressure tested this is dangerous due to the high pressures and temperature of water.

    2) Pic 3 - The heating element seal is gone and has been leaking for some time, the element might be damaged but you may be lucky that it works OK once cleaned up. You will need to find a large socket and remove the heating element and clean in a descaling solution, before doing so you will probably want to scrape off or dremel as much of the calcified gunk as you can. You will need to remove the existing heating element seal and order a new one (if the boiler is repairable).

    You have a couple of choices from this point;
    1. Professional technician repair - I don't think this is viable as a new boiler is likely $300+ and heating elements often $100-$150 then you have labour costs on top.
    2. Donor machine / parts - Put up a wanted ad for a used Mia boiler and heating element or a full machine which is non-working but with a solid boiler
    3. DIY - Assuming you can get the hole in the boiler repaired and pressure tested then the other items are doable (clean, test and re-install heating element) if you are patient and fairly hands on. You will also need to bank on rebuilding (at least replacing rubber cam seals in E61) and descaling the E61 group as it is likely neglected.
    4. Cut your losses and resell the machine or go back to the seller and ask for you money back. The machine looks like it has been run into the ground and potentially never had a professional service.
    Dimal, robusto, Burkeyboy and 1 others like this.

  9. #9
    Senior Member robusto's Avatar
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    Good diagnosis Roosterben. I agree. Unfortunately looks bad. Not sure there should be a gasket on the autofil, but it looks shot anyway. That hole should be hissing audibly.

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    If you have a look at this photo that I also uploaded to Sulloís Mia rebuild thread, my Mia has the same Ďholeí in the boiler top.

    It does not go all of the way through.
    The top of my boiler it also looks a bit of.
    This s because every time the machine heats up some water spits out of the anti-vac valve onto the top of the boiler as thee is no cup around the valve to catch the water like some other machines have.

    Now the bottom of my boiler looks nothing like the picture above.

    Peter

  11. #11
    Senior Member robusto's Avatar
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    Interesting. A deliberate half hole, I had a laugh. With respect to the anti vac valve, mine ( Grimac eclisse) vents to the air, there is no collector, but no water staining either. I expect most of what comes out of it during heat up/ pressurisation, to be just hot air. The same air that was sucked in to equalise pressure during cool down.

  12. #12
    Mal Dimal's Avatar
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    That 'hole' may be threaded and optionally used for Over Temperature protection t/stat...

    Mal.

  13. #13
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    Help needed with Grimac Mia temp

    Iíve watched mine heat up with the top off the machine and the anti-vac valve always spits some water out as as the water in the boiler boils but before the valve closes.

    Not much, but enough to wet the top of the boiler slightly and it then evaporates off as the boiler reaches temp. You can hear the water sizzle occasionally as it evaporates, just depends how much spits out.

    Anyway this doesnít help the OP.

    The corrosion on the bottom is way more than could come from the top of the boiler and needs to be cleaned off and the boiler checked for damage. At the same time the element can be checked to make sure itís ok. I have a spare so if you want a picture I can upload one.

    What puzzles me is that if the boiler wonít reach proper temp because itís leaking, you should be able to hear the water boiling away inside the boiler and some sort of noise made by the pressure leak.

    Peter
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  14. #14
    Senior Member noidle22's Avatar
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    The thermosyphon restrictor likely has scale or some other debris partially blocking it which will cause the group head to run too cool.

    If you remove the upper group head to HX pipe, there should be a small disc or insert in the fitting or pipe, usually at the HX end. Inspect it for any scale.

    If it all looks fine, it's possible it was fitted aftermarket and is too small. You can enlarge the hole very slightly and retest. If you see an increase in temperature then that was your issue.

    You'll want to get the machine to a stable brew temp at a max of 1.4-1.5 bar, I wouldn't want to push it any further than that. Enlarge the hole in small increments to achieve this. It's quite time consuming.
    Dimal, robusto, CafeLotta and 2 others like this.

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    Senior Member Jackster's Avatar
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    If only externally adjustable restrictors were available ..
    I have seen them on something big and commercial, I expect that is to allow for different pour temperatures at each group

    Here is the blockage I got out of one of my machines. It was a cold shot even with boiler wound up
    IMG_20190729_104719.jpg
    IMG_20190729_105237.jpg

  16. #16
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    Quote Originally Posted by Jackster View Post
    If only externally adjustable restrictors were available ..
    I have seen them on something big and commercial, I expect that is to allow for different pour temperatures at each group
    Faema did an adjustable flow restrictor on some of their older machines, not sure if they came to Australia though. Read about them in an A1 manual for one of the sub-models.
    Slightly different than the way a HX restrictor works though as the Faema don't use a HX, rather use in-flowing water to stabilise temperatures. Adjusting that flow can mean the output temp at the shower is altered.
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  17. #17
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    They were fitted to an e-61 Legend I saw.

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    Quote Originally Posted by noidle22 View Post
    Faema did an adjustable flow restrictor on some of their older machines, not sure if they came to Australia though. Read about them in an A1 manual for one of the sub-models.
    There's a thread on HB about them - https://www.home-barista.com/espress...lve-t4815.html
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  19. #19
    Senior Member Jackster's Avatar
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    That was the one I saw..
    The HB topic suggests it opens up more tuning problems.
    Good link! Thankyou. Been a while since I was thinking about restrictors
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  20. #20
    Senior Member Sullo's Avatar
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    I dragged my mia from garage, do you guys need any pics from mine?
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  21. #21
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    Quote Originally Posted by Jackster View Post
    If only externally adjustable restrictors were available ..
    I have seen them on something big and commercial, I expect that is to allow for different pour temperatures at each group

    Here is the blockage I got out of one of my machines. It was a cold shot even with boiler wound up
    IMG_20190729_104719.jpg
    IMG_20190729_105237.jpg
    Some La San Marco models had externally adjustable restrictors - they were a rotating cylinder inside a housing turned from the outside with a screwdriver, to align one of a number of different sized restrictor holes with the outlet of the housing.

    I have seen a Rancilio (Classe 9, from memory) that needed several warming flushes before an extraction due to severely blocked HX restrictors - with the boiler at normal operating pressure the water from the groups was lukewarm until a lot of water had been flushed through.
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    Thanks for all the detailed responses. My father in law is a bit of a genius with anything machine/electrical/engineering and he thinks the most likely cause is a scale build up on the outside of the HX pipe within the boiler. The element switches on and off normally and there is plenty of heat for steam. Can anyone outline how to descale these machines? I'm trying to avoid removing the element if possible as I'm lazy by nature
    Cheers, Steve.

  23. #23
    Senior Member Jackster's Avatar
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    https://youtu.be/yEGfyJkWSqU

    Someone else posted this link recently. It will do for a start.

    Noidle is a qualified genius in the realm of coffee machines, yet you choose to heed your fatherinlaw after asking for help here.

    Good luck with the descaling, I hope that is what it is.
    Dimal likes this.

  24. #24
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    The small disc on the thermosyphon restrictor looked clean. I've taken on board all the advice given here Jackster and am working through things step by step. I've also ran the advice past my father in law as I trust his judgement through years of seeing him problem solve the tiniest issue up to full rebuilds of coffee machines, vehicles, sewerage systems, you name it. It's not that I dismiss the advice given here at all, but when I have a master electrician/technician/mechanic on hand here, why wouldn't I use him in conjunction?
    Jackster likes this.

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    disc.jpgmushroom.jpgMaybe scale isn't my primary issue. This mushroom looks not too bad? As the disc on the thermosyphon looked ok, maybe a slight enlargement could be useful as suggested. Is the first picture I think is the disc on the HX end of the pipe.
    Last edited by Burkeyboy; 2 Weeks Ago at 12:38 PM.

  26. #26
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    There's probably a more significant scale build-up in the boiler, given the state of the Mushroom...
    What sort of water filtering do you use?

    Mal.

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    Hi Mal. I've only just picked up the machine. It was used in central Brisbane so not sure of water type. It has an in line water softener in the tank which looks quite built up. I've ordered a new one.
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  28. #28
    Mal Dimal's Avatar
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    Would be worth your time, trouble and money to research some 'Under Sink' water filter options, or an on the counter one. Would be much better than the short lived units placed inside the water tank...
    https://coffeesnobs.com.au/brewing-e...reading-3.html

    Mal.

  29. #29
    Senior Member Jackster's Avatar
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    My blockage was on the other side of that disc...

    Can you ask you fil about my hot water system... Bloody thing
    Burkeyboy likes this.

  30. #30
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    unaligned.jpgClean up going quite well. I'm having trouble realigning threads on the top of the boiler. Eg, the HX elbow on the top, when I tighten properly it's out of alignment with the pipe going to the top of the head, maybe 15 degrees or so. I've tried a teflon washer I had on hand but this leaves me almost half a turn too short. Can't work out how this has happened. Any ideas?
    Last edited by Burkeyboy; 2 Weeks Ago at 04:04 PM.



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