Hi there,

First of all, I've managed to tear down the Cremina and changed all the gaskets/seals yesterday. So many thanks to Orphanespresso for providing the information and parts!

However, after I've changed the seals, a problem has arose. I noticed that the coffee puck always has a dent in the 12 O'clock in the locked-in position. I pulled 4 shots so far and the dent is always there, at the same place every single time. I am sure I did not get that before the rebuild. I even take the group out again and make sure everything is inserted correctly.

During the rebuild, the only thing I did not change is the rod cup seal in the cylinder that requires a snap ring pliers. But the machine itself isn't in a bad shape because all the gaskets I replaced, except the boiler gasket, were in pretty good condition and has some (little) elasticity to them. The rod cup seals felt pretty rubbery as well when I touched it with a needle probe. May I know what is the function of the rod cup seal? Will it cause that problem?

The holes/dent on the puck seems to be caused by a strong water flow at one spot. But when I pulled up the lever without pf, the water seems to coming out "quite" evenly. Could take a video if that is needed for diagnosing the problem. There should be channeling occurring also because the espresso stream does not come out in a straight stream as it used to be.

Here is an imperfect picture just to get the idea. The puck is pretty fractured as I knocked it out and then only decided to put it back to take a photo. If needed, I will take another photo tomorrow.



Thanks for helping!

Very, very likely that is caused by uneven flow from group head. I don't know why it would start happening after rebuild though, possibly cleaning changed the flow.

Two things you can do:

1. Pull lever slower at the point where the water is let into the group head so you do not have strong stream to wash the hole into the puck.

2. Tamp harder, 30 pounds or more so surface of puck is firm and does not wash away easy. This is very important if flow out of group is uneven.

Hope this helps.

Dennis,
Thanks! I did pull the lever up at a very slow pace. I normally pull the lever up at about 9 o clock, just before the water comes out, before locking in. Then I slowly pull it further up, pause for a short moment to let the water fill in the headspace, then only slowly move the whole thing south.

I am very confused by how this could happen too. Before this, I was using the same technique, with the same plastic tamper , but this has never occurred. It must have been something went wrong in the group rebuild, but the water seems to come out more gentler than before. Does your water come out from the side of dispersion screen also?Because mine does, even before the rebuild.

I am still very curious about the rod cup seal's function. It's the one deep inside the group cylinder. I am suspecting it's just to prevent water from leaking through the top of piston shaft, right?

Here's a video of the water flow:

Some possibilities.....Is you screen clean? Are all the holes clear? It looks like water is jetting out sideways. is it possible that you used too much lube and it is fouling the screen? In your photo the edges of the screen look pointed as if it may not be the original screen...could be an illusion from the pic.
Do you have an idea of the pstat setting?

The rod seal keeps water from leaking out of the top of the group, as you surmised and would not effect the flow.

Thanks Doug for your help, I really love your videos on the Cremina restoration by the way! They're life savers!

I checked the screen, it's clear. The water is jetting sideways ever since I got it. So I thought that was normal. And yes,the screen is a little pointy, but it looked original to me. I am posting some photos here since I got insomnia from the late evening iced latte.

Pretty sure I used very little lube. I only applied a very very thin layer of it using my finger to spread a small bit of the lube. I don't think I would scratch up any lube using my nail across the cylinder surface.

For the pstat setting, yes. Thanks to your steamwand pressure gauge. I set them around 0.8-1.0 bar.


Looking clear..





Do I need to replace the screen?





Another video, definitely it doesn't look like the water come out from the screen until I go up further. It's all jetting out from the side. Is this normal? The piston cup seal is supposed to be cup-up(U) at the top rim and cup-down(n) at the bottom, did I mess that up?

Another 2 pulls this am. Same dent in the same place of the puck. One with about 5lbs of tamping, the other with 30lbs of tamping. The water flow seems ok. But there is always a hole in the puck in the 10 o clock area in locked-in position(not 12 o clock as mentioned). I am at a loss right now.

5 lbs tamp:


30 lbs tamp:


The picture is not taken at the same angle. I tried to find the best lighting to show the dent but ended up with different orientation. But it is on 12 o clock in the basket, corresponding to 10 o clock position when locked in.

If this is truly a sudden change immediately after a rebuild, is it possible the piston seals were put in upside down? That might account for a sudden radical change in water flow.

Another possibility, the four small holes around the edge of the piston can sometimes accumulate gunk and will benefit from cleaning. As usual, Orphan Espresso has the perfect tool for that cleaning.

http://www.orphanespresso.com/Espresso-...1556.html#

Those brushes can also clean the hole where the water enters the grouphead from the boiler.

Michael,
The piston seals is cup up (U) on top rim on the piston and cup down (n) on the bottom rim, is that right?That's what I saw on the forum anyway and I installed it that way.

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I did used a needle to clean the 4-holes on both the piston faces. If one of the holes ggot clogged, I think the spot get dented on the puck will be different if I turn the piston shaft 180 degree. Will have to try that later. I think I will try putting the old piston seals back and see if that changes anything.

PLEASE, someone find out what is going on. I have had channeling from the same exact spot for so long I can't remember. I ALWAYS get a huge tunnel coming from that exact spot. The last time it didn't channel there was once a few months ago (a great shot!). I barely use my cremina anymore that my roommate has an isomac TEA that I can't get to channel if I try. I just ordered an Elektra basket in the hopes that it would help.
One thing I thought of is that when I poked my dispersion screen holes they might have gotten bigger? I haven't ordered a new one since they are very expensive for some reason. Another thought is that the water comes in from the boiler, hits the grouphead and bounced to that 12 o'clock position. One other thing is that I did NOT descale the tube that sticks into the boiler, so it may be directing the flow one way or another. I'll go home and pop out the dispersion screen and check it, but i'm fairly sure it is all clear and installed correctly.

Please find a solution. Don't do it for me, do it for my Cremina.

Sam

I didn't notice before I sent my post that you had mentioned the piston seals installed correctly. Just shooting in all directions trying to hit something that might help but not meaning to cause doubt or extra work. With that in mind...

One thing I notice in your photos is that the dispersion screen gaps seem really far apart and the sides seem pushed out too far. When I look at my screen from the angle of your "Looking clear..." photo I cannot see the gaps and sides at all. The sides one mine are all tighter in towards the center and the gaps are narrower. If your screen is a loose fit that may account for more water gushing out the sides than the bottom. Even if the screen was this way before your maintenance, if your changes improved the water flow, the effect may be more pronounced now than before. Perhaps you could push in the sides evenly all around to make a tighter fit and reduce the sideways flow.

Perhaps the only fate worse than not having a Cremina is having one that is not working well .