Yeah, that's true. That's the little hypothesis that I come out with given my situation. It might not be correct because that's the explanation that I came up with to relate my problem and the act that solves it. You know, I really wish I was wrong that the seal is not the cause, rather than being right and pay $$$ to Olympia.

So, again, late in the night, I take off the seal. Change the seal. Put the new seal in with the teflon taped screen that reduced side jetting problem. Warm it up. Pulled a shot. Spot on again. I am just frustrated that why my machine isn't acting like what it is supposed to be. There is something going on with the new seal and my machine. They are just not compatible to each other.

Old seals:

New seals:


Result:


I used a pretty dark sacrificial bean for the experiment so it probably isn't that obvious on the photo. But it's there and it's real. This is saddening !!@!@

And I don't think the screen is the cause for that problem. The side jetting is greatly reduced now. If anything, the divot should be appearing in random position. Not that one spot.

Gotta change that back in the morning tomorrow. =( I am off to bed now.

bostonbuzz wrote:This is frustrating, especially considering how simple the cremina is. It's making more sense to me how the seal/piston is deflecting the water straight down and perhaps a shorter seal could solve this problem. However, EVERYONE should be having this problem, and they aren't. So what's the deal?

3 other options I just thought of:
1) lift the lever quickly to get the piston past the intake valve
-but this is universally shunned for good reasons I think.
2) lower my pressure setting
-I'm fairly certain that it's fine though, I had checked it a while back.
3) Put some secondary screen in like someone already mentioned.
-but this is treating the symptoms, and i want to fix the problem!

Someone will chime in...

O, and thanks Doug/barb for that video, you're awesome!

That's what I am wondering also! Why is this happening to both of us, but not others? Your screen definitely has no problem. Good luck to you.

I swear I did not do anything nor touch the puck with my finger!! The puck is from this morning's espresso. Overextractedly bitter due to the channeling. I officially give up trying it, until I have the time to cut & shorten the seal. The water seems flowing out evenly from the screen but when I make espresso this is what happened:

I really suspect the "gap" for the seal is not enough. My theory could be wrong but the evidence really suggests that the seal's the problem. I can consistently create the meteor crater just by changing the new seals back in and problem gone as soon as I change the old seal back in. With serious side jetting on the old seal, I do not get the crater. But with the new seals and reduced side jetting, the crater is there. 100% of the time in the same spot. I am 100% positive about this. This viton seal definitely give a smoother lever action and I personally like it too. Up until the point I see the crater or when my preinfusion leaks within 2 seconds.

The divots normally don't look as deep in the photo as they are to the eye. But the fact that it is apparent in the photo showed that the "seriousness" of the depth of the crater.


Doug (Orphanespresso),
if you're still reading this, could you do me a favor and measure if the outer height of the seal is 8mm from edge to edge(the measurement when the outer seal is pressed down,simulating the situation when it's pressed inside the cylinder wall)?For reference, the inner height I measured form edge to edge is 7mm. It's either my piston is off or this particular batch of seals is out of measurement.

Could you also look at the top of my post about the gap between the seal and rim, does that seem off to you or is it perfectly fine? Thanks!

So I figured out a partial solution. I removed the group to and looking down at the piston I noticed that of the 4 holes one of the wasn't evenly spaced. With the piston raised, the hole wasn't lined up with the intake hole from the boiler. I spun the piston 180 degrees and now the hole lined up!
I did a test, but I had terrrrible chanelling just like before. I lowered the P-stat and checked the shooting and it seems to have somewhat subsided (maybe 50%). With my new bigger basket and some luck, hopefully in the morning I can pull a decent shot. Update tomorrow.

I'd try turning the pressurestat down more. From what you are writing it sounds like you are experiencing trouble as a result of the inflow pressure and temperature being too high.

Cheers

Mike

I continue to get the problem, but less so now, especially with lowering the p-stat setting. I may be getting a little crazy now, so let me know, but I found the same problem in the orphan video. At this point, however, I don't think it's a big deal, since it's so short-lived and not so extreme. I also am not convinced it's the seals at all, just the nature of the piston machine. Here is a screenshot of the vid. This only happens on the first pull, and it's not a problem as far as I can tell in the later ones. Even if the first pull had coffee, I don't think it would have caused channeling.

Hi BB,
Did you get to the bottom of this?

Cheers,
Paolo

I lowering the p-stat helped slightly, and a good cleaning helped as well. The problem still persists, but not quite as bad. The channeling usually occurs later. I have not ordered new (old style) seals yet, but I may in a few weeks. I've given up on the stock basket, and I'm currently experimenting with the elektra double basket (around 16g).

My pucks DON'T have the channeling problem that the Cremina basket has, but I have switched one problem for another. Instead I have side channeling big time. I have 5 places where water drips from. Four evenly spaced places around the portafilter, and a 5th in the middle of the basket. I'm tempted to think that it's due to my botched home bottomless conversion. I probably didn't cut the bottom out enough of the PF, and the new basket is so large that, due to some fluid dynamics, the espresso likes to go OUT to the pf rim instead of IN to the center.
However, the shot wouldn't still taste bad if this was the case, so I'm fairly sure I have a side channeling problem.

Anyway, for the purposes of this thread, I still have a problem and if I can't sort out my new basket, I'll get the olympia gaskets and post my findings- which will hopefully be like samuellaw's. If not, there will be a Cremina up for sale, since I haven't come close to the daily shot quality of my Le'lit pl41 (not to mention my housemate's Isomac TEA, which I can't mess up a shot if I want to).

Fwiw, I fit close to 20g into the Elektra double basket. Some of your photos do look to me as though the problem may be just due to underfilling, improper tamping and possibly coarse grinding.

I measure 17gm into an Elektra double basket and that seems right for my use.