The Espresso Machine Restoration site
A non-commercial site for those interested in espresso equipment repair and restoration.
||La Marzocco GS2 Solenoid Valve
|Reassembly of the groups and boiler - also "How to assemble the old style La Marzocco brew boilers".
What is it with me and cracked brew boilers? Every single machine I get requires some welding to the brew boiler. This
time the cut-outs for the groups on the boilers had cracks. They were repaired, it looks a bit messy but seems to have
done the trick.
1. Start off with a clean and dry brew boiler and group(s). The boiler had been cleaned in a acid bath and was
2. Lock the boiler inside a workmate with the position slightly elevated so you can access the group holes more easily.
3. Have ready your NEW retaining bracket and the 8 brass nuts.
4. Put the 8 nuts inside the steel bracket BEFORE you put into the boiler.
5. Now for the fun part! You must get the bracket and the 8 nuts inside the boiler without any of them falling out. It is
tricky but possible.
6. Once it is inside and in roughly the right place, thread some bolts through to loosely hold the bracket in place.
Eventually you want all 8 screwed in. Screw a bit of each one at a time so you do them all up evenly - don't just do 1
completely otherwise the bracket will be skewed.
7. Once all 8 are in place you need to bend the 4 tabs, these tabs help to position the bracket securely otherwise their
position will change and you cannot put the group on. I use a combination of plier, mole-grips and a goodl old hammer
to do this.
8. After you have done all of them have a break!
|Putting the group onto the boiler
It is important at this stage to take it easy, relax and sometimes I have left it for the next day. You really only get 1
chance to get the attachment of the groups done, if you are stressed-out or angry then you WILL cross thread the 8
bolts and you have to start from the very beginning.
9. So now you are relaxed and calm. Make sure the groups are ready (clean and dry) and that you have on hand you
NEW 8 hole gaskets and your sealant. I use loctite 573 flange sealant which is food safe. Lightly brush BOTH sides of
the NEW gasket, don't pile it on you need just a waffer thin (mint) amount. I then hold up the group in one hand and
thread two bolts through and then put the gasket on - the 2 bolts stop it moving around.
10. Now transfer this to the boiler and using you 2 bolts the gasket should be in the correct place. Then I look through
the group holes and see if they are roughly in the correct place.
11. Now is THE most impt. and tricky bit. This is make or break time. Very slowly put bolts in 1 at a time. Gently push
them through until you feel it touching the brass nut. Gently turn the bolt clock-wise to "feel" if it has threaded
properly. Usually you can do about 4 very easily. Try and get all 8 in - your aim at this point is not to tighten anything,
just to get all 8 bolts to thread into the nuts. If you feel that it is hard to turn the nut back off immediately otherwise you
may cross-thread the nut and you need to start all over again with a new brass nut.
12. ONLY when you are confident that all 8 are threading correctly should you tighten them. Now you need to tighten
them in sequence at various torque values. With the group facing you as if you are making coffee, the top left nut is
no 1. and go clock-wise around the nuts. No. 2 is the top middle, no. 3 is the top right and so on. The tightening order
is as follows: 2 - 6 - 1 - 5 - 3 - 7 - 8 - 4. Using a torque wrench, I then do a round of 10nm, then 12nm and then
|Bench-testing the boilers
If you have successfully managed to get this far, then you have done well - really well. The GS2 gold 3 group boiler
was actually very straightforward and after having the retaining brackets in place took around 30 mins to get all 3
groups on. Compare that with the 1 group GS manual and that 1 group alone took an entire day!
An impt. step is to perform a heating and cooling cycle on the boiler BEFORE you even think about installing it in the
machine. A couple of things to bear in mind is that you must let the boiler and the group expand and contract and
then you tighten the bolts up further. Also if I remember correctly the green goo is anaerobic which means it cures
when it gets squished between the group and the boiler under pressure.
The following is what I do - I am an experienced cowboy, er I mean electrical engineer and feel comfortable
doing this. Do so at your own risk.
What I do is plug all holes, install the heating element but do not put the brass group covers on. Fill with water enough
so that the element is covered but not enough so that it will spill out through the space left by the group covers. Very
carefully you need to get power to the element but safely and always connect the ground. When the water and the
boiler is around brew temp. I turn it off and let the boiler cool. I then drain the water and fill again with fresh cold water.
After about 10 mins when I am sure the boiler is stone cold I then re-torque all the bolts - you would be surprised how
loose they have become. At this stage when you tighten them you may get a little squeek which I believe is a good
Now I will install the group covers and the solenoid valves, plug in to the mains water and fill her up, bleeding off the air
of course. I will usually leave for a day or so like this. Undoubtedly you will get a few leaks from the nuts and you can
torque them up. If you have any leaks coming from the gasket itself, you can try and tighten all the nuts to see if that
helps. If it still leaks it's time to take a holiday.
|The frame has been repainted
The frame was the part I was dreading the most, but once it was done it made such a transformation to the project.
From then on it was just a case of reassembly. In a few pics you can see a contactor switch - the best time to do the
wiring and layout of new components is now whilst you have space to work. Also in the background you can see piles
of boxes, those are my bumper knockboxes.
|This website is created by Paul Pratt, Hong Kong 2004-6. If you would like to use any of the images or text I am sure
I will say yes, but please ask first!
Email me here.