Londinium coffee roasters
Cleaning the inside of the sight glass on an Olympia Cremina lever espresso machine
If the sight glass on your Olympia Cremina has become unsightly, with specks of dirt, grit, and other contaminants appearing then one day it will probably annoy you enough to start thinking, I wonder how I go about doing that task?
In this post we show you exactly how to go about it.
The sight glass of the Cremina we are working on looked like this before we began work on it:
As you can see, various bits of green debris have accumulated inside the sight glass, which isn't particularly attractive
These 4 tools are all you need for this job; a flathead 3.5mm or similar sized screwdriver, a Phillips No.2 screwdriver, a 12mm wrench and a 19mm wrench.
The first step is to remove the boiler cap from the Cremina and invert the whole machine over a sink to drain the boiler
The second step is to remove the casing, which most of you will be familiar with I suspect (unscrew the boiler cap, then unscrew the decorative chromed washer. This allows you to lift off the top plate. You can then remove the casing by carefully lifting it up and tilting the casing back slightly as you lift it up;
The reason I am posting this 'how-to' blog entry is I had hoped that I would be able to remove the sight glass by leaving the top and bottom fittings that the site glass mounts into in place, and simply undoing the nuts that connect the sight glass to the fittings, as I have successfully taken this approach with the Olympia Maximatic machines in the past. On the Cremina I managed to undo the bottom nut, but not the top one, so it became clear that I would have to remove the mounting blocks for the sight glass, a proper job if you like.
So, the third step is to take the 12mm wrench and remove the top pipe connection to the boiler (as shown in the image below). I suggest undoing the sight glass side (left) first and then the boiler side, but I don't think it matters too much.
Then use the 12mm wrench to remove the bottom pipe that connects the sight glass to the boiler. Don't use brute force! If you take a look at how this pipe connects to the boiler you will see it is quite a small diameter pipe. If you try hard enough I'm sure you could crack this weld and then you'll have an expensive fix on your hands.
With the top and bottom pipes removed you are now in a position to remove the sight glass mounting blocks. But before you do, there is one more small screw to remove, here:
This small screw in the bottom right hand corner of the face plate screws into the bottom sight glass mounting block, hence the need to remove it in order to remove the sight glass block.
Now you are free to take the Phillips No.2 sized screwdriver and remove the lower of the 2 Phillips screws that are clearly visible in the vertical side frame of the Olympia Cremina.
Once you have removed the lower Phillips screw there is nothing holding the bottom sight glass mounting block in place - it is now dangling on the bottom of the sight glass, which in case you are wondering is glass, and yes it is easily broken.
Now place the Phillips screwdriver in the top screw, but before you unscrew it take your left hand (assuming you are right-handed) and take a firm grip of the top sight glass mounting block as the moment the screw relieves the tension on the block it will start to twist out of place as a result of the pendulum effect of the lower mounting block swinging off the bottom of the sight glass.
This movement will very easily and quickly break the glass, so please take note of this step.
Now the whole assembly of top and lower mounting blocks and site glass will be held in your left hand. With extreme care manoeuvre it out of its position in against the frame and remove it from the machine and lie it down very carefully on your work surface.
Another import step: BEFORE you loosen the 19mm nuts that secure the sight glass to the mounting blocks you need to accurately measure the distance between the mounting blocks as the glass tube is not designed to butt fit hard against the mounting blocks - a small gap needs to be left at both ends.
You can see in the second image in the blog post, the one with the piece of paper with the tools sitting on it, that I have drawn a rough pencil sketch showing the two mounting blocks and the measured distance between them in the Cremina in question was 145mm. This measurement (145mm) should be common to all Creminas but it is possible the on your particular Cremina that this distance is slightly different, so PLEASE measure this distance BEFORE you loosen the sight glass at either end or you will have a real pig of a job on your hands to get this distance just right when you come to refit the sight glass assembly!
Then take the 19mm wrench and very carefully loosen (counter-clockwise) the nuts that secure the sight glass at each end. If you twist the wrong way and start tightening the nuts you will most likely crush the sight glass, so take your time and get it right the first time. As you loosen each nut use your left hand to press the mounting block to which the nut is attached hard against the work surface you are using. The nuts will not be screwed on very tightly, you may even be able to remove them without the 19mm wrench. Once the nut is free it will slide up the sight glass. When you slide the nut along take care to keep it lifted off the painted outside surface of the sight glass tube, as the paint scratches off easily, and if it does the marks where the paint has been removed will be highly visible when the sight glass is re-installed.
Between the nut and the mounting block will be an o-ring washer which will no longer look like and o-ring as it will have taken up the shape of the space into which it has been compressed. Given that the sight glass is a bit of a pain to get to it is prudent to replace these o-ring seals, rather than putting the old ones back in. The o-ring seals will slide easily off the sight glass.
You will now have the bare sight glass in your hands. As already stated, be mindful that the paint is on the outside of the sight glass and it is incredibly easily to remove, for example rings on your fingers will scratch the paint very easily.
Then take the 8mm bottle brush (available here), wet it thoroughly and be careful not to score the inside of the sight glass with the twisted wire head of the bottle brush as you enter the sight glass with it. A couple of sweeps with the bottle brush should remove all the grime from inside the sight glass, if not you may need to add a little Sunlight dishwashing liquid or other mild detergent to ensure it the sight glass comes up sparkling clean. Rinse thoroughly in water to ensure all traces of cleaning agent is removed.
I also took the opportunity to soak the mounting blocks in a descaling solution, as I don't expect to be accessing these components again for a long time and want to keep them in top condition.
Slide a nut onto the sight glass, with the thread facing outwards. Then slide on an o-ring seal. Then present the end of the sight glass carefully up to the mounting block. Make sure you get the bottom mounting block on the end of the sight glass with the black minimum level marking on it. The bottom mounting block is different from the top mounting block and can be identified by the tapped hole in it that the small screw that secures the face plate of the Cremina screws into, that you removed a short time ago.
Using only your fingers tighten the nut down on the mounting block, taking care to ensure the white painted surface of the sight glass will end up on the back of the machine when you reassemble it, otherwise you will be taking it all apart and trying again. Also take care to get the white painted sector aligned so that when you view the sight glass 'square on' from the front of the machine that the white painted portion of the sight glass is not skewed to the left or the right as this will annoy you every time you look at it.
Do the same thing to the other end of the sight glass, i.e. slide on the nut, then the o-ring seal, then present the remaining mounting block. Again, only use your fingers to tighten down the nut that secures the sight glass to the mounting block.
Now you will have the sight glass loosely connect to the top and bottom mounting blocks. This is a good time to check that the bottom mounting block is on the end of the sight glass that has the black minimum water level line marked on it. Also press the mounting blocks down on your work surface to ensure they are sitting 'square' or 'in-line' if you prefer. The flat face that the large Phillips screws goes into is an easily identifiable face to use on both mounting blocks for this alignment task.
Now you are ready to take your ruler and measure the gap between the top and bottom mounting blocks. As stated earlier, on the machine we took apart this distance was 145mm. We would hope it would be similar for all Creminas, but be aware that it may not be. As you have only done the securing nuts up by hand you will easily be able to reduce or increase the length of this gap. Try to get an equal amount of 'free space' between the end of the sight glass and the mounting block at both ends of the sight glass. i.e. if the distance between the mounting blocks is 140mm and you need to increase the gap to 145mm try to slide the top and bottom mounting block off by 2.5mm each, don't take the 5mm all off the top or the bottom or it is likely that the o-ring will be tightening down on the very end of the glass tube, thus increasing your chances of breaking the glass tube as you tighten the retaining nuts.
You should now have the correct distance between the top and bottom mounting blocks and be ready to tighten the nuts down. Be very careful not to over-tighten. On the balance of probabilities it is much more likely that you will break the sight glass as a result of over-tightening than it is that the sight glass will leak as a result of under-tightening. I am tempted to tell you only to do them up by hand as tight as you can, but this may not be quite tight enough in some cases. So use the 19mm wrench, but do so very timidly or all you good work up to this point will be for nought. Only use forefinger and thumb to operate the wrench. You will also need to hold the mounting block down on your work surface with your free hand to stop the whole lot twisting around and getting out of alignment.
If you tighten them up as tight as you can by hand, then I think something a third of a turn with the wrench will be all that is needed. Go slowly. Do not expect the mounting blocks not to still have movement in them relative to the sight glass when the nuts are sufficiently tight. There will still be quite a lot of play, so don't keep tightening the nuts in an effort to eliminate this play as you will break the sight glass.
Now you are ready to re-fit the sight glass assembly.
Carefully move it into position and check that the holes for the Phillips screws on the mounting blocks are lining up with the holes in the vertical frame of the Cremina. Then screw the top Phillips screw in, but don't tighten down. Then screw the bottom Phillips screw in. Then carefully tighten the top Phillips screw. Then tighten the bottom Phillips screw. Then screw the small screw for the face plate back in with the flathead screwdriver.
Have a look from the front and check that the sight glass is in the correct way (minimum line to the bottom) and the white paint is at the back of the sight glass and not the front. If so you can congratulate yourself on a job well done as the difficult bit is done.
Now take the 12mm wrench and re-attach the lower and upper pipes that connect the sight glass to the boiler. Again, take special care not to over-tighten the lower pipe as it is a small diameter pipe welded directly to the boiler, which could easily be damaged by brute force. You will notice that the upper pipe does not have this weakness, so you don't have to be quite so careful. Tighten the nuts up just until they are snug. DON'T force the nuts with the wrench, they only need to create a seal, a job they are designed to do and will do without excessive force being applied.
Replace the casing on the Cremina. Put the top plate back on. Screw down the large chrome retaining nut on the boiler filler thread. REFILL the boiler and observe the water filling up in your now sparkling clean sight glass. Replace the boiler cap as you normally would.
- Reiss Gunson
- 2012 Mar