Help: Espresso boiler project has hit a steel wall

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#1

This is the boiler from my espresso machine. You might be wondering why it’s out of it’s normal home nestled up against a web of wires and tubes. Well I thought it would be a good idea to attach a better temperature gauge in the form of a PID controller. And while it was out, wouldn’t it be good to clean out the limescale from inside the boiler and fix a new gasket? How naive I was…

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(Many rounds of effort take place to remove the bolts. Vinegar soak, blowtorch, whacking the bolts with a punch, with only one result)

I’m now faced with the reality that I have 1 sheared off bolt, and 3 bolts which appear to be completely stuck. These bolts have been in place for 20+ years, and I’m guessing some kind of corrosion has led to a weld like situation.

Has anyone had experience drilling out bolts at the maker space? I’m guessing that’s the next step, short of buying a replacement set of boiler and grouphead.

#2

From a Gaggia Classic? Have you considered (or are you already doing) https://gaggiuino.github.io/#/? Its amazing and not any more difficult than the normal PID mods. They also have a pretty active discord that maybe able to advise on removing the bolts.

Also I would suggest trying a bath of Citric Acid or more industrial descale solution to get at any remaining limescale. You may have to destroy the bolts to get them out, but you could probably re-tap the holes to salvage the boiler.

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#3

before you destroy it further, impact wrench (we have milwaukee in space) + penetrating oil (proper, not wd40!)

ps. why do you want to disassemble it? descaling can be done without

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#4

Hi, :smiley: citric acid (food grade ) will clean it up really nicely . a torque wrench would be great for the bolts . Keep well . Brian D=

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#5

Are the bolts steel and what are they screwed into - aluminium? Knowing this will help tremendously…

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#6

Hi,:smiley: :thinking: the best way to know what the metal is made of is with a magnet . I hope the coffee machine makes a full recovery (a fellow coffee drinker ) . Brian D=

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#7

Hey everybody, thanks for all the ideas It does seem like getting proper penetrating oil would be a good idea at getting the remaining 3 bolts out. That and drilling seem like the only two things I haven’t tried

I’m pretty sure the boiler is aluminum and the bottom group head is steel. I’ll try the magnet trick to see about the bolts themselves. I’m guessing this is the galvanic corrosion I’ve read about.

I need to drill out or find another way to get at the bolt with the sheared off head. Is this something anyone has experience with?

#8

Thanks for the tip on the impact wrench. I bought a simple impact wrench, but need to find the right size bit for a 5-mm head.

I still need to find out what to do with the sheared off bolt though, which I’m guessing would have happened if I used the impact wrench?

Yeah, I have been back flushing it pretty regularly too descale it, but I suspect there’s still quite a bit of buildup in there after 20 years of use. Servicing a boiler like this seems to be a pretty well known maintenance routine in the coffee community from what I can tell.

#9

I’m not deep into boiler servicing, though I have an old espresso machine that I descale using citric acid. Citric acid is quite more efficient at 100°C than at room temperature and is a good chelating agent (removes reaction products into solution), so if you used it in the past I doubt there’s a significant amount of limescale there. You can probably check if acid stays active after descaling. I have certain doubts in disassembling the boiler idea, which is designed to be sealed pressure vessel (ie do not explode). Can’t you fit sensor somewhere on outside connectors?

On impact wrench, I would still recommend using the one in space I mentioned, this specific one has a lot of power which helps here.

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We also have a set of hex heads (part of our socket set) and extensions. Bolts may be damaged in the process, they’re sort of consumables where serious mechanics is involved. Drilling them is a last resort option tbh because you don’t want to damage hole thread. Instead it may be possible to shim/modify existing head or weld something (like another bolt) on top of it.

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#10

Phosphoric acid for steel to aluminium corrosion. It’s in coke (the beverage). ATF and acetone also works for most seized bolts.

Impact driver may well sheer the remaining bolts.

I’ve removed many sheered bolts like this on the past FWIW… Drill and tap, drill and helicoil thread repair, drill fill and retap, tig weld nut and remove - these are all potential solutions.

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#11

Looks like a cast Al alloy body, as you suggested, and the bolts are probably steel, so galvanic corrosion is the likely issue.

I deal with GC a lot. First port of call is penetrating oil (note @scythian there is a Wd-40 brand penetrating oil that is quite good) followed by localised heat (targeting the Al body, which will expand more readily than the steel bolt). If a bit of force doesn’t loosen it after than, there’s several techniques you can try, depending on your level of urgency.

  1. Cool the unit. If it weren’t a pressure vessel I’d suggest freezing it, but why take the risk of cracking a vessel or deteriorating a seal when you can just put it in the fridge or leave it out at night to get good and cold. Once cold, apply penetrating oil and heat to the alloy body, and try quickly to remove the bolt while there’s a temperature differential between the two materials.

  2. Use an impact driver after a cold+oil+heat cycle.

  3. Repeat cold+oil+heat+controlled torque process a few times.

  4. Weld a key or lever in place. Just a tack should do. If you round out the bolt heads on a previous step can still do this.

  5. Use a screw remover drill bit. Might have mixed results with this.

  6. If the bolt head is unusable or has sheared off, ldrill out the bolt. Looks like the work space is restricted so you’ll want to use a dremel or a long drill bit think. Start small and go slow.

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#12

Stud extractor might also be appropriate - like this….

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#13

I’ve never worked on coffee machines but do have a 52 year old VW and this happens too often with steel bolts and studs in the aluminium cylinder heads.

Steel bolts corroded into aluminium are incredibly difficult to get out - sorry.

Try @hernehillier suggestions but don’t hold your breath.

A stud extractor might help, but they can also snap in the hole and make life even harder.

Are you taking about the bright cap heads near the bottom of the picture?

If you’ve started and have to continue, cut the heads off, you can then separate the two parts leaving the bolt shanks sticking out of the bottom half. Then follow @hernehillier’s directions and use good quality molegrips, or this type of extractor https://www.ebay.co.uk/itm/142852535571 (if they’re long enough) to try and turn the bolt shanks out or try and weld something onto them, not easy but the extreme heat changes might help loosen them.

If that doesn’t work, it might but be prepared for it not to, cut off shanks and drill out the remainder of the bolts very very carefully. Use the drill press. I wouldn’t bother with stud extractors, just oversize the holes and then use threaded inserts to repair them bottom half. Something like a helicoil or make your own, something like this https://www.ebay.co.uk/itm/256220622469

(Apologies for any typos, predictive text on my phone does weird things sometimes)

Good luck and keep us posted on progress.