I removed for cleaning the diffuser screen on my La Marzocco GS/3. On replacement onto the group assembly, however, I cannot seem to get it as tight against the group assembly as I believe it was when I removed it.

The screw appears to be tightened all the way (i.e., flush), but even though I cannot push the screen further up, I can still without much effort rotate the screen horizontally along the diameter of the group assembly.

Why do I care? Two things. I believe I am getting uneven extractions as a result. When I examine the flow of water (without the portafilter attached), it seems as if some water is coming over the sides of the rim instead of through the screen. Just a little bit, but even without that I doubt the machine is designed to have the diffuser screen be capable of rotation around the group assembly, What is more, is that even when I run continuous flow, occasionally the water stops before I want it to. I don't know if this is related. Perhaps it is a separate problem. By the way, I have the new firmware which contains the rinse cycle.

Any ideas? I have examined the diffuser screen and screw, and neither appear to be damaged or bent. Still, I'd be happy to order a new set, if this would solve the problem.

Thanks

Andy

Questions for you are:

Can you screw the center screw in all the way in absence of the diffuser screen, and does the screw turn freely? Both screw and group are stainless steel. You can gall the threads through overtightening, which will cause you all sorts of headaches. Generally this screw should be snug, not crunched-down overtightened. And you should be able to easily turn it with your fingers.

I quickly checked my Linea (also stainless steel group) and my dispersion screens don't rotate, although I can't really crank on them because they are hot.

-Greg

Assuming the diffusion block and screens haven't been re-invented for the GS3 (ie they are the same as the Linea and GB models), the diffusion screen is normally very slightly convex if viewed from the coffee side and the screw is a firm fit against the screen. What you describe sounds like an inverted screen. This normally results from many cycles of expansion of the puck against the screen during brewing. It is exacerbated by overdosing. Sometimes you can flex the screen with your fingers to bend it back temporarily, otherwise you need a new screen. I assume the screw thread is not jammed or otherwise damaged. I can't offer any advice about the "less than continuous" flow problem. Is that button programmable? Are you saying the flow is continuous sometimes and not others? Is it really continuous or does it have a maximum volume or time limit?

GRB

I think there is no any problem with the machine... I have a little bit simpler machine but the same shower screen and screw. But I use LM ridgeless filters or little filters from Wega

I wish I have the gs3 for its giggler and pid --- it is much more forgiving than Linea But my Linea is also very forgiving

gscace wrote:Questions for you are:

Can you screw the center screw in all the way in absence of the diffuser screen, and does the screw turn freely? Both screw and group are stainless steel. You can gall the threads through overtightening, which will cause you all sorts of headaches. Generally this screw should be snug, not crunched-down overtightened. And you should be able to easily turn it with your fingers.

I quickly checked my Linea (also stainless steel group) and my dispersion screens don't rotate, although I can't really crank on them because they are hot.

-Greg

The screw does turn freely, but without the screen it does not go in so far that the screw head is flush. When I first got the machine and pulled off the screen to clean, I remember being confused and trying to unscrew the diffuser screw when I was actually tightening it. Made it pretty tight I am afraid, but then it came off without a problem and I didn't think I stripped it. How would I know?

Thanks

Andy

GRB wrote: I assume the screw thread is not jammed or otherwise damaged.
GRB

Please see my reply just above. It does not appear to be jammed or damaged, but on the other had it does not appear to hold the screen so tight that it cannot rotate. It is pretty darn close, but not so tight that it does not rotate. I don't think the screen itself is misformed.

Thanks

Andy

Try to clean the diffuser with a blind filter and some pulycaff. Once I have seen such a loose shower screen in a GB5, but it was not a critical error. The new screen will probably solve your problem...

antonio wrote:Try to clean the diffuser with a blind filter and some pulycaff.

Thanks. I use Urnex Cafiza Cleaner. Is there a difference for these purposes? Certainly my current cleaner did not help, but I did order a new screen and screw today. Hope that helps. But the screen I have now looks so good that I am concerned it won't make a difference. A few days will tell.

ONE MORE PIECE OF THE PUZZLE.

Around the time I started having this problem, I noticed that when I pull off the portafilter from the group assembly - with empty basket inserted into the portafileter (after it has been inserted all night and warmed up by the group head since I have programmed the machine to turn on automatically in the wee hours of the morning) - sometimes the basket sticks to the edges of the group head, instead of coming off as part of, and with, the portafilter. I have to pry the basket (which is kind of hot and has now detached from the portafilter even though I believe the spring is good) off the group assembly.

I have to believe this is related to the "problem" of the rotatable diffuser screen.

Anyone?

Mine does that too. I attribute it to an old gasket that I need to replace. I never torque the PF to 6:00 when I don't have it loaded and ready to pull a shot. If the basket is empty, it never gets locked in all the way.

Thus far, I haven't had my group screen off.