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Is my Silvia dead?

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  • Is my Silvia dead?

    I think my beloved 12-year-old Miss Silvia is dead, but I'm open to contrary opinions!

    She had developed a very slow leak from her boiler, so I ordered a new gasket and set about on the open boiler surgery operation. Unfortunately, the boiler screws were pretty heavily corroded, and the heads on four of them snapped off when I tried to undo them. One snapped screw I could maybe extract, but four... I think it's beyond me.

    Replacing the boiler would be do-able at ~$250, but it looks like I'd have to replace both the boiler and the group head (another ~$230). And who knows what would be next? Her steel frame is showing corrosion as a result of the leak...

    For almost $500 and no guarantees, is it better just to... let her go?

  • #2
    The boiler will probably be corroded inside and around the o-ring gasket groove.
    (If the Silvia is similar to the Gaggia)
    Grinding off the heads of the bolts will allow separation of the boiler and group head.
    The group-head should be fine just need to use RostOff or 50/50 acetone/Auto transmission fluid to loosen the corroded bolt(use a dropper to add a few drops every 5 minutes and leave for a day or two).
    Grab the ends with mutligrips and they should come right out.
    Then you can either replace the boiler or use a piece of wet and dry sandpaper on a piece of plate glass to re-face it.

    Then sell it and upgrade.

    Comment


    • Dimal
      Dimal commented
      Editing a comment
      Don't believe there will be significant corrosion as such, maybe some accretion of precipitated dissolved solids which can be removed relatively easily.

    • amberale
      amberale commented
      Editing a comment
      Ooops she’s brass so Dimal’s right(again ).
      Gaggia Classic is ally and rots.
      The last set of corroded bolts I removed I used a few drops of CLR on them over a couple of days.

  • #3
    Perhaps post up some pics for the experts here.
    Might be able to help you with the screw extraction.

    Comment


    • #4
      Not a great pic, but shows two of the busted screws and some of the corrosion. Thanks amberale - I had assumed both the boiler and the group head were threaded. But you're right - if only the group is threaded, I should be able to remove the boiler. Back to the operating table...
      Attached Files

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      • #5
        Progress update. Got the boiler off (which I didn't think I was going to be able to do.) Next challenge: extracting five broken screws...
        Attached Files

        Comment


        • #6
          Time is your friend.
          Rostoff, or CLR(calciumrustlime remover) or acetone(nail polish remover) and wd40 should all work BUT it takes time.
          sit the boiler with bolts on top and put a few drops on the bolts so they soak down.
          Repeat, repeat, repeat.
          Don’t try to undo the bolts for a couple of days because if they snap it will really be a real pita to get them out.
          After a couple of days use a pair of small vice grips to wiggle the bolts back and forth.
          If they are loose undo them, if still stiff, lubricate again and check the next day.
          That’s how I’d do it.

          Comment


          • 6ftbrl
            6ftbrl commented
            Editing a comment
            Thanks amberale. I've had some success. Two screws out with some WD-40, vice-grip pliers and brute force. But still three to go and stuck fast. I'll try to be more patient with the penetrant options!

        • #7
          Then clean up the surface, retap the threads in the portafilter holder, new gasket and put back together with SS bolts with nickel based antiseize on the threads.

          Comment


          • 6ftbrl
            6ftbrl commented
            Editing a comment
            Thanks! I'd never heard of nickel anti-seize, but I've just looked it up... perfect!

        • #8
          If you have rusty steel bolts in a brass boiler, oxalic acid is your friend. You can buy it at hardware shops as "Diggers rust and stain cleaner". Oxalic has the interesting property of reducing iron oxide to the hydroxide and rendering it soluble. It will dezincify the brass surface but this will only be skin deep.

          Another ancient trick is to soak the things for several weeks in a 10% solution of molasses, which will also reduce the iron oxide and dissolve the hydroxide but much more slowly. On the other hand it won't affect the brass as much.

          If you are impatient, heat the brass as hot as you can* using a gas axe or an oven. Brass has a higher coefficient of thermal expansion that steel, so the holes will expand more than the bolts. Brass also conducts heat well so you will need tongs or similar to pick it up.

          * don't go too far above dull red heat: brass melts at about 900 C which is a full cherry red.

          Comment


          • 6ftbrl
            6ftbrl commented
            Editing a comment
            Thanks Lyrebird! I have some oxalic acid deck cleaner. I'm not sure how it compares concentration-wise to the Diggers (which is a powder you mix with water, whereas mine is already a liquid) but we'll see how we go... The gas-gun sounds like a last resort!

        • #9
          Deck cleaners are usually around 20% oxalic. You could try applying it directly to the bolts and see how it goes.

          BTW if you wipe over the brass with grease or vaseline before you start, the oxalic won't be able to reach the brass surface so it won't dezincify it.

          Comment


          • #10
            Thanks everyone for your suggestions and encouragement.

            Unfortunately no amount of penetrant, acid, flame-throwing or elbow grease could turn the three remaining stuck screws. The galvanic corrosion seems to have all-but welded them to the brass.

            I have, however, drilled them out, albeit imperfectly. I don't have a drill press, so I centre-punched and drilled from the underside.

            I'm thinking that I can re-join the group head and boiler with longer bolts and nuts - rather than screws threaded through the group head.

            I also think I'll use fibre washers, to provide some electrical isolation between the brass and stainless steel (although noting it might be pointless, as there is still contact between the two metals at the bolt shank). And definitely some nickel anti seize.

            I'll post on update, wish me luck!
            Attached Files

            Comment


            • #11
              Proof of concept seems sound. Finally starting to feel a bit more optimistic about this operation!
              Attached Files

              Comment


              • Dimal
                Dimal commented
                Editing a comment
                Looking good there mate...

              • kofekitt
                kofekitt commented
                Editing a comment
                Looks good, but doesn't that lip of the boiler sit on a ledge, and those bolts/nuts may be in the way? Hope i'm wrong...

              • 6ftbrl
                6ftbrl commented
                Editing a comment
                You're absolutely right kofekitt. It does sit on a ledge of the steel frame. I've drilled two holes in the frame, and I will bolt right through.

            • #12
              Don’t forget spring washers on those bolts.
              Looking good.

              Comment


              • Dimal
                Dimal commented
                Editing a comment
                Actually, Shake-proof washers work a lot better in this situation, I've found...
                Or even the use of s/steel Nyloc nuts.

            • #13
              Thanks amberale and Dimal. I'll use nylon lock nuts underneath and spring washers on top.

              I'm treating the frame now. The rust wasn't too bad. I've filed it off and am treating it with phosphoric acid rust converter. Then I'll give it a rust-inhibiting primer and an epoxy enamel top-coat.
              Attached Files

              Comment


              • #14
                Originally posted by 6ftbrl View Post
                Thanks amberale and Dimal. I'll use nylon lock nuts underneath and spring washers on top.

                I'm treating the frame now. The rust wasn't too bad. I've filed it off and am treating it with phosphoric acid rust converter. Then I'll give it a rust-inhibiting primer and an epoxy enamel top-coat.
                I’m not sure how nylon lock nuts cope with heat, I normally use spring or lock washers in those situations(eg engines, boilers).
                I have found the rust converter with sealer works better for me.
                My worst case with just the sealer was on some galvanised stock yards I had for sale.
                I applied the converter to some light rust around welds and checked it in the morning.
                Note to self : galv and Phosphoric acid don’t mix.
                I prefer a product called Xtroll for rust conversion.
                Similar to penetrol but better.

                Comment


                • Lyrebird
                  Lyrebird commented
                  Editing a comment
                  Nylon lock nuts don't cope with heat well. Nylon loses most of its strength above its glass transition temperature which is about 50 oC for Nylon 6.6

                • 6ftbrl
                  6ftbrl commented
                  Editing a comment
                  Wow, there is such a wealth of engineering knowledge on this forum!

                  Perhaps I'll give the nylon lock nuts a miss then, but I will use the spring washers. Given that the original fittings had neither (and weren't stainless) and they lasted 12+ years, I'm reasonably confident these should give me a few more good years!

                  The rust really wasn't too bad. I'm not convinced the phosphoric acid did very much at all, but grinding it off and painting it surely will. So far it's had two coats of Rust-Oleum primer and I will give it a top coat of Dulux epoxy enamel. Worst case: I have an old frame which I have been meaning to get sandblasted and powdercoated...

              • #15
                On the home straight.

                Her new boiler is bolted down with Hammerbarn's fanciest marine-grade stainless steel bolts. They've been lubed up with nickel anti-sieze (bought a 250 g tin and used about a quarter of a gram) and locked down with spring washers. Everything is tightened to within a tenth of a newton-metre of stripping the threads.

                Her new gasket has been moisturised by fancy Japanese silicone-grease designed for underwater camera housings.

                And her black frame has had four coats of rust-inhibiting spray-paint and is glistening like obsidian under a midnight sky.

                Now... can I remember how to put her back together? And, will she hold!?

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