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Thread: Cimbali Group Head leak

  1. #1
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    Cimbali Group Head leak

    Gene Cafe Coffee Roaster $850 - Free Beans Free Freight
    I've got a nice and compact Cimbali M32 Bistro DT1 that's had its group head seal replaced by an engineer (not faulty or leaking - just 6 months usage). Sadly it blew 45 minutes after use. I've tried replacing with Cimbali group head seals of 8.5mm and 9mm conical without success. I've inserted 2 x .8mm shims/spacers as well and it still leaks.

    Can you let me know what's going wrong please. Is my group head distorted? Or is it my porter filters (both single and double) that are worn (although there's no sign of undue wear and tear)? BTW, I thoroughly cleaned out the recess before inserting seals etc, and second BTW, it didn't leak like this before.

    Many thanks

  2. #2
    Senior Member artman's Avatar
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    I didn't notice this post, I replied to your other one.

    In addition, make sure your group collar is correctly installed and tight. There is nothing really in the group that can go wrong.

    The group and collar are huge chunks of brass, very solid.

    Cheers

  3. #3
    Super Moderator Javaphile's Avatar
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    Quoted from original thread for clarity:

    Quote Originally Posted by artman View Post
    Did you get the conical seal? Is the group nice and clean where the seal sits? On mine a very thin film of "stuff" forms behind the seal over time (despite regular back flushing and cleaning ) but it's quick and easy to remove the collar and seal and give the group a good clean/scrub. If you remove the collar and seal you will soon see what's going on.

    Cheers

    Java "Original thread closed" phile
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    Quote Originally Posted by Javaphile View Post
    Quoted from original thread for clarity:




    Java "Original thread closed" phile
    Apologies Javaphile

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    Quote Originally Posted by artman View Post
    I didn't notice this post, I replied to your other one.

    In addition, make sure your group collar is correctly installed and tight. There is nothing really in the group that can go wrong.

    The group and collar are huge chunks of brass, very solid.


    Cheers
    Cheers Artman

    I agree it's a big chunk of brass. Just can't fathom out why the seal should leak though. I've cleaned it thoroughly, and seated the seal squarely using the porter filter.

    I inserted a 9mm conical seal with 2 x .8mm shims yesterday - and it still spitting water out. Aaaaargh. The porter filter yesterday was locking in and tightened up so the handle was in the 6 o'clock position, it's now in the 4 o'clock position. Very confused.

  6. #6
    Senior Member artman's Avatar
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    Have you taken the collar off to have a good look to make sure it's squeaky clean? Tried it without the washers? Doesn't really matter if the PF locks in at 5 or 4. Is the collar centred correctly and the three collar bolts tightened evenly?

    Does it leak with another basket/blind?

    Seems strange, there is nothing really to this group, it's a very simple and robust design.

    Cheers

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    Artman thanks for your advice

    The collar is squeaky clean - as far as I can see. There's no debris up there. I'll check to see that the collar is centred correctly today.

    It leaks like a sieve without washers as it does with a single or double PF. Same problem when using a blind.

    It also loses water down the waste pipe - a lot more than normal. In fact I'd say I lose half the water when it's brewing. If that makes sense. The waste pipe feeds into a half gallon bucket, that bucket never use to be quarter full. Now it's full at the end of the day.

    No idea what the engineer has done. Sorely tempted to buy a new group head and start afresh.........

  8. #8
    Senior Member artman's Avatar
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    Is yours the rotary pump?

    It sounds like you may have an issue that mine had. The pump bypass (brew pressure adjustment) was jammed causing the pump (and hence brew ) pressure to go sky high and the over pressure valve was trying to dump the excess pressure by dumping the water into the waste whenever the pump was activated. The pump flows a lot of water so pressure at the group was way over 15 bar (it maxed out one of my gauges ) This would also mean that the group seal will struggle to seal the extra pressure.

    If this is the issue it is easy to fix if your are that way inclined. You can remove the pump bypass and check the piston moves freely. Mine was jammed up, I stripped it, cleaned it and lubed with food grade grease and it was good to go. You will need to reset the brew and OPV pressure.

    Cheers

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    Cheers Artman - you are a font of information.

    I'm not too sure if mine has a rotary pump - but the symptoms you've described are very similar.

    Sorry to be slow witted here, but where is the rotary pump and bypass? I'm fairly capable of stripping the bypass, just not sure where it is, plus I use it 6 days a week in my tea room.

    Do really appreciate your help by the way - cheers

    PS is this the rotary pump/bypass I need to locate and fix? Part number 25?

    http://www.astramgroup.com/EspressoM...FAEMA-FA20.htm

  10. #10
    Senior Member artman's Avatar
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    No probs. the link you sent, the part number 25 is the pump which bolts to the motor (part 22). This is a rotary pump setup, the motor is quite large, can of baked beans type size. And they operate almost silently. The vibe pumps are very noisy in comparison and quite small, about the size of a couple of boxes of matches. Google "ulka pump" for images. If you take the panels off your machine it will be obvious which pump you have.

    If you look at all the variations of part 25 in your link, the very left domed type nut is the pressure adjuster/bypass. The outside nut is the lock , the inside bolt/screw is the pressure/bypass adjustment. On mine, the setup is slightly different, have a look at this thread:

    http://coffeesnobs.com.au/brewing-eq...-question.html

    and specifically the pic in this post: http://coffeesnobs.com.au/brewing-eq...tml#post263615

    If yours is the same, unbolt the entire adjustment mechanism (green nut) and see if you can move the piston (pics further down). If you dont touch the locknut/adjuster, then in theory if your pressure was set correctly prior to the issue, you can free the piston, clean, lube etc and bolt back in and it will be back to what it was. its simply a spring that preloads the bypass.

    Not sure if the domed nut setup on the pumps in your link are any different?

    Its all quite straight forward if you are the tinkering type, just take your time and note the order of the parts.

    ideally get a pressure gauge so you can set the brew pressure (9bar) and over pressure valve (12 bar) correctly. Pullman "hires" one: http://coffeesnobs.com.au/brewing-eq...tml#post513396

    Cheers

    Cheers

  11. #11
    Senior Member artman's Avatar
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    Forgot to mention, you can adjust the pressure while the pump is running and see the changes immediately on the gauge. Standard electrical safety, live machine disclaimers etc etc etc...

    Cheers

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    Many many thanks mate, much appreciated. Shall be having a look later today or tomorrow - that's if my customers don't lynch me for switching the machine off and denying them their coffees!!

    Cheers

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    Artman - in my eyes you have the status of a god. The OPV was well and truly stuck. Only took me 15 minutes to remove it, 15 minutes in citric acid (vinegar), 15 minutes back and and Roberts your uncle.

    Many thanks mate - so very much appreciated.

    Testing it tomorrow proper when we open up tea room, to see whether the GH/PF seal still leaks after I change it. Will keep you updated.

  14. #14
    Senior Member artman's Avatar
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    No probs at all, glad I could help.

    I presume you mean the pump bypass was stuck? The OPV is what dumps excess pressure when the pump is creating too much pressure.

    Cheers

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    Quote Originally Posted by artman View Post
    No probs at all, glad I could help.

    I presume you mean the pump bypass was stuck? The OPV is what dumps excess pressure when the pump is creating too much pressure.

    Cheers
    That's the one. Working fine now - just need to change group head seal when it arrives. Can't understand though why I'm having to use a 9mm seal with a .8mm paper gasket - do you think my porter filters need changing?

    This is what I used before fixing the valve

    La Cimbali GROUP SEAL,GROUP GASKET - Detailed item view - Coffee machine spare parts,Espresso coffee machine spare parts Jura spare parts

  16. #16
    Senior Member artman's Avatar
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    You should be able to see if the lugs on the PF are worn, but I would say that would be unlikely.

    Have you checked to make sure the group collar is secured tight up against the group head?

    With just the conical seal from coffee parts my PF locks in at around 5 o'clock position. The shape/height of the basket lip will also effect the lock in position.

    Cheers

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    Quote Originally Posted by artman View Post

    Have you checked to make sure the group collar is secured tight up against the group head?
    I'll check the group collar today. Again, many thanks.

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    Quote Originally Posted by artman View Post
    Have you checked to make sure the group collar is secured tight up against the group head?
    Hello Artman, I've checked the group head collar and one of the bolts is missing!! Now I need to find a replacement one that the engineer lost.....

    When adjusting the bolts, is there anything I need to be aware of, do they adjust the position of the collar etc?

    The front view (2nd photo) shows a distinct lopsidedness to the left of the collar - and that's where the PF is still leaking from. It's all beginning to make sense now.
    G H Side.jpg


    G H Front.jpg

  19. #19
    Senior Member artman's Avatar
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    You have the same machine as me! As an aside I removed the left side auto frother (mine was also missing the plastic bits needed to make it fully functional) and associated solenoid and piping, blanking off the boiler at the corresponding outlet. Makes the machine look cleaner.

    Re the bolts , they are listed on coffee parts. There are two versions, the normal bolt style you have and an Allen key variety that looks nicer, which I believe is for the machine versions that do not have the plastic shroud around the group.

    Remove all the bolts, remove group and seal. Soak group in caffeto or similar solution. Clean and rinse.

    Have a look at the group surfaces where the seal sits (vertical and horizontal). Over time you get a fine layer of black "stuff" sticking to the brass. Scrub and clean it all off.

    Take off, soak, clean rinse etc the shower screen while you are at it.

    When fitting the collar, just make sure it's nice and snug upwards against the group , rotate it so the collar holes line up with the group holes. Insert bolts and get finger tight. Then tighten progressively each bolt tighter and tighter around a circle until snug.

    The bolts have a tapered shank so help centre and locate the group. I applied some food grease to the bolt thread and tapered face as mine were starting to corrode lightly.

    It's all very straight forward, I am sure you will work it out when you do it.

    What steam tip are you using?

    Cheers

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    Many thanks for the reply.

    Lovely little machines aren't they. Our pumps out approx 60 to 80 coffees a day ranging from Americanos, lattes and cappuccinos. The steam wand I have looks very similar to the one here:
    Coffee Parts | La Cimbali Spare Parts - Steam and Water Inlet Valves

    more like the second one. The nozzle is more bullet shaped with a centre hole and three on the very edge of the nozzle.
    I don't bother with the auto frother - too fiddly. The wand creates a good foam and that's the main thing.

    Occasionally the machine will lose pressure to the point of no steam and no hot water to brew with. The pressure and water level lights come on. Takes a couple or three minutes for it to fire up. This happens about once a day - which can be annoying when mid brewing/steaming.

    I've also noticed the steam wand will sometime not have enough pressure and will drop to a faint hiss - does yours do this?

    We've let outside "engineers" tinker with it in the past - but after this past experience, that is not going to happen, plus they're expensive. I'm beginning to learn a bit more and am willing to have a go myself.

    Apart from that, we love the machine and will pay more attention to it - give it some TLC.

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    Quote Originally Posted by b9drinker View Post
    Hello Artman, I've checked the group head collar and one of the bolts is missing!! Now I need to find a replacement one that the engineer lost.....

    When adjusting the bolts, is there anything I need to be aware of, do they adjust the position of the collar etc?
    There's a distinct possibility that only part of the bolt is missing, and the threaded part is still there, snapped off inside the body of the group head........

    Those bolts are notoriously easy to shear off if corroded, or if the collar is not aligned exactly with the bolt holes before the bolts are installed. The collar needs to be worked into position so all 3 bolts (lightly lubed with copper antisieze compound) can be screwed in fully just using your fingers, then given a final tighten till snug, not overtight. It's tempting when reassembling a collar to simply push it on enough to get all 3 bolts started in their threads, then tighten them with a spanner and use the tapers to help push the collar into its final spot. Or to push the front of the collar up high enough to get the front bolt started, then use that as a pivot point when levering the back of the collar up into place. Either method puts a lot of side loading on the bolts right at the base of the threaded section where they are at their thinnest, and they will start to crack there. I have worked on a few where the bolts sheared off as I undid them, or as soon as gentle pressure was put on them to tighten them with a spanner, presumably as a result of a previous repairer's efforts damaging them.

    I suspect that since this is a very uncommon head design, few repairers really know how to work on them properly, so a lot of them end up a bit damaged. As far as a replacement bolt is concerned, I believe there are actually more than 2 types. Last time I had issues with one of these heads, I decided to carry spare bolts for next time, and went through our scrap machines to collect a few spares. I do remember collecting a couple of each type (10mm bolt head and allen key type), but when comparing them to the bolts on the next Cimbali I did I found there are actually more variations - I can't remember for sure if it was the taper, length or both that varied.

    I can say that you really don't want to break a bolt off in the head and have to fix it - I have had to do just that when the right hand rear bolt sheared off on a customer's machine as I was removing the collars. The bolt broke off inside the threaded hole, so there was nothing to grab with pliers - I ended up having to remove the whole group head from the machine and carefully drill out the sheared bolt, clean out the threads, refit the head and reseal the HX that it bolts onto. Not a fun job!

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    MorganGT, thanks for the response. Hopefully it's not sheared - will check it out tomorrow after work. Fingers crossed hey?!

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    Quote Originally Posted by MorganGT View Post

    I can say that you really don't want to break a bolt off in the head and have to fix it - I have had to do just that when the right hand rear bolt sheared off on a customer's machine as I was removing the collars. The bolt broke off inside the threaded hole, so there was nothing to grab with pliers - I ended up having to remove the whole group head from the machine and carefully drill out the sheared bolt, clean out the threads, refit the head and reseal the HX that it bolts onto. Not a fun job!
    I had a quick look and the rear left bolt has been sheared off - I think but can't prove, the engineer did it. This doesn't sound at all good.

  24. #24
    TC
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    One for the not good enough files...

    We had a VBM DJ come in for service this week. There was no plastic cover on the boiler pressure gauge.

    The machine had been serviced by a bloke in country Victoria who "lost" it. Returned the machine to the client with a "Oh yeah. We noticed that it had gone missing. Here's your full-priced invoice."

    Fortunately, we had a spare....

  25. #25
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    An update on the sheared bolt in the G H.

    Managed to dismantle the GH and extract from the HX. Friendly VW mechanic down the road extracted the sheared bolt. Rebuilt, replaced gaskets/seals. All is working very well. All completed in 4 hours.

    Quite surprised how easy it was to dismantle and rebuild. Crema is even better too....

    Many thanks for your advice and support.

    Best wishes........

  26. #26
    Senior Member artman's Avatar
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    Good work. Yes , appears these machines have been designed with serviceability in mind, they are great to work on.

    Cheers



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