A couple of years ago, I gave my father a Gaggia Classic espresso machine for Christmas. The Gaggia Classic is, in my opinion, the best value for a home espresso machine that uses a commercial type portafilter and has good frothing abilities. The only thing this machine is lacking is a double boiler - but that would significantly raise the cost of the machine.
Unfortunately the hard water where he lives clogged it up. This happened on my machine as well after about 4 years. The symptom is lack of pressure when it is on the brew cycle - but the pump is still able to pump through the frothing wand.
The cause is a clogged three-way valve and/or brew group. This shows how to fix both.
Here is the subject:
Cleaning out the three-way solenoid
The first thing you should do, obviously, is take all the loose accouterments off the machine. I then ran the pump for a few seconds to pump water out of the system, not specifically required, but it keeps water from leaking on your work surface. Definitely make sure it is unplugged and cool before attempting to take anything apart.
The machine enclosure is welded on all sides, so access is through the top. To gain access to the machine, undo the two phillips screws on the top of the machine:
You will then be able to access the insides of the machine. Looking at this machine it is really a marvel electronics are still made like this. It is like a 1960's Fender amp with point-to-point wiring - except the Gaggia has removable connectors at each point! The wiring and connectors are all ridiculously overbuilt for home use. The removable wiring and components also makes the machine easy to rebuild and maintain (like cars used to be).
To make some room to operate, I unplugged the wires from the on-off switch and also the side of the three-way switch (It is the black cube piece with the yellow round metal label on the top - this is what you are trying to access). You should write down which color wire goes to which connector so you don't forget!
Remove the tube from the top of the three way solenoid. I used needle nose pliers to squeeze the hose clip and then pulled off the tube.
Now you can see the three way solenoid at the top center of this picture with the tube removed. Remove the 14mm nut, washer and yellow metal washer. Slide off the magnet (the black cube)
Now remove the two 4mm allen bolts from the front of the brass piece holding it to the machine chassis.
These will be a bit of a squeeze to get your hands in there with the allen wrench. Now you can remove the brass part of the solenoid.
Here it is:
Look in these two holes, then take a pin or other small metal piece and clean out all of the scale. The hole on the right is the real problem as it has the smallest aperture and is prone to clogging.
Now you have to take off the large brass nut and clean out the insides of the solenoid. I found the best way to do this is to screw the solenoid to a 2x4 to be able to apply torque to the assembly. I think this bolt is a 23mm nut, not having a metric wrench that big - a 15/16" wrench will also work.
Here it is attached to a 2x4 with the wrench. I used some drywall screws to hold it down:
Now you can see the two small apertures inside the solenoid:
Clean these out well with a pin or other small metal piece. Make sure the spring mechanism will move in its sleeve.
As they say, reassembly is the reverse of dis-assembly. Make sure all of the wires are firmly back on their terminals.
Cleaning out the brew group:
Turn the machine over and remove the phillips screw holding in the shower screen:
Remove the two 5mm allen screws holding the brew group together:
Now remove the gasket. This is best done by using a screw to pull it out. Screw in a wood screw, then use pliers to pull out the gasket.
Screw in drywall screw to gasket and pull out:
Now you can remove the brew head. This can be easy or hard depending on how much scale is holding it on there. This is my second time doing this. The first time I had to gently pry it up (put the pry device where the arrow is in the next picture) this time, it just came right out.
I have read other places where they suggest adding some de-scaler here if it is hard to remove - or threading a longer screw down the center to push it out. I did not have that much trouble getting it out.
I took a brass brush to remove all the scale in the brew head. You can see a small hole where the water is introduced. This area usually has more scale around it - clean it all out:
Once everything is cleaned out, insert the new gasket and bolt everything back together in the reverse order.
Run a cleaning cycle with de-scaler, then you are ready to go for a few more years of service!