Post by drgary » Yesterday, 10:32 pm
You can also grind a touch coarser or downdose and preinfuse long enough so drips come into the cup. If you're using a bottomless portafilter the drips should start to distribute themselves evenly, then slow down. This ensures that the coffee cake is thoroughly infused with water and all the air has been driven out. Half pumps as described above also help infuse the coffee cake and drive out air.
Tried domico's half pump with the steam tap open suggestion, but no luck. Also tried your advice to adjust dose and grind, but also no luck.
There is a vigorous gurgling when the water enters the group, and some hissing too. There appears to be channeling in the same spot each pull, but I know my distribution/tamp is decent since my pulls were good prior to servicing the piston seals (aside from a few spritzers as my HG-1 burrs break in). The coffee puck looks wet and violently disturbed on top, and there is quite a bit of ground coffee on the dispersion screen. Prior to the group maintenance, the coffee puck was tight and dry, and the dispersion screen was always clean as a whistle. Worst part is, the espresso tastes vile...I could deal with a spongy pull and dirty screen if the drink was good.
I decided to remove the group, disassemble and inspect (again). This time I found the upper piston rod seal was damaged, so maybe this is the culprit, however there are no signs that the damage has resulted in a bad seal between the group and piston rod. I have a new one on the way from Cerini's so we'll see.
A wild guess of a theory...is it possible that water being sucked in from the boiler could flash boil as it enters the group, if the pressure gauge I use to set the p-stat is wildly out of calibration? Per my pressure gauge my boiler is cycling between 0.8-0.9 bar, but if the gauge is off, who knows.