I recently ran into some problems with my Gaggia Classic pre 2015.
Anytime I start pumping (without a portafilter inserted or even when group head is taken off), the OPV opens and water flows back into the tank. The water flow from the group head thus only starts with a delay of a few seconds. I am under the impression that no water should flow back into the tank when no portafilter is inserted. The same happens when I turn on the steam switch. The OPV stays open and I can't get any pressure to steam.
I thought maybe the OPV is set too low so tried screwing it all t