Frozen hex screws on Rancilio Silvia boiler

Equipment doesn't work? Troubleshooting? If you're handy, members can help.

#1: Post by »

I need to replace the leaky boiler gasket on my Rancilio Silvia V1. The 6 hex head screws all seem to be frozen, with two showing rust. I'm afraid of applying too much pressure, and would like advice before proceeding. I have currently applied some EvapoRust, but I understand it needs time to work, and I don't know if enough can seep down the threads. I'd appreciate any solutions.
Bob Gall


#2: Post by robmack »

I don't have a Rancilio but if the hex screws are steel and the boiler aluminium, it's probably corrosion that has frozen them in place. Definitely use a penetrating oil on the threads to work on loosening things up. Let the oil work overnight. Forget the store-bought fluids; The best penetrating oil you make yourself - 50% acetone and 50% automatic transmission fluid. Also, use heat on the boiler where the screw enters the aluminium to expand the boiler. It doesn't hurt to insert a hex ratchet bit into the head of the screw and give it a couple good blows with a hammer to loosen the screw. When you are ready to undo the screws, don't try using a hex key. Rather, use a ratchet and a very good fitting bit and apply firm even pressure to turn the screw while pushing firmly downwards on the ratchet to make sure the bit remains engaged with the head of the screw and doesn't pop out. That could strip the head. If you end up stripping any of the hex socket holes, then jam a slightly larger Torx bit into the stripped hole. The Torx bit should be slightly large, enough that you have to hammer it in to make it fit. Eventually, you'll win over the boiler. Don't apply too much torque to the ratchet as you risk snapping the screw. Alternate between applying counter-clockwise pressure to the ratchet to loosen and then clockwise pressure to tighten. Work at breaking the corrosion bond.

When you reassemble the boiler, use copper grease on the threads of the screw to prevent this problem from occurring again.
- Robert

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#3: Post by Davi-L »

Hello, RobMak answered very well. All that I would say. I've found that keeping lots of fluid in the threads helps. And time. Maybe a few days if the bolts don't turn. I've used a cordless impact screw driver for these jobs with success.


#4: Post by JRising »

It's steel in Brass, they've rusted and bonded, but with a lot of penetrant and patience you can get them out. If you get over anxious and break some off, it's best to remove the bottom half as well so you can use heat along with penetrant and learn from your mistake about not using enough patience.

In good news, Rancilio has replaced those old black bolts that rust when a leak is ignored with shiny new stainless bolts that also rust when a leak is ignored. Maybe they won't bond and seize as well. (original poster)

#5: Post by (original poster) »

Thanks for the reply. Just to add to this record, the Silvia boiler is brass and the screws seem to be steel, but not stainless. So I need to attack the really bad rusted one. Good idea about the Torx, because the rust has started to plug the hex hole. I'm going for the penetrating oil next.

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#6: Post by hankbates »

Brass screws in brass is preferable to either the steel or stainless option.
While the use of steel screws or bolts is obviously bad, the use of stainless can also cause problems.
Stress corrosion cracking of the stainless can leave a threaded section in the brass which is very difficult to remove, as it is much harder than the brass, and it work hardens when drilling out.


#7: Post by terryb99 »

I have two Silvia. One mfg '98, the other '99. My father really liked my Rocky/Silvia combo, so I bought him one for Xmas in '99. I got it when he passed away a few years ago.
My '98 built one, has a damn flat head screw holding in the screen. I have tried multiple times over the years to get it out without destroying it, but have pretty much given up. The'99 built one, has a hex head bolt. It comes out fine with a 5/16 socket.

I actually found this forum/site to help troubleshoot a different problem, but maybe I will try some of the methods above and get that damn screw out, lol.