Hi All: Every so often (once a week or so) my Astoria single group auto makes a "clunk" sound at the end of a shot. I have not observed any problems with pulling any shots, even the shot followed by the "clunk" or the one after. I am guessing that this is the group solenoid (I think also called the 3way valve, right on top of the group) but I can not imagine what could cause such a distinct sound just occasionally and not interfere with coffee production. Machine is 15 years old from new in home service.
Any ideas?
Thanks, KDM

Has it always made this sound or is it a recent development?

My machine sometimes makes an odd CLUNK when the drip tray heats up when flushing, which causes it to flex.
Happen to have a video demonstrating the sound?

Recent development, don't know when to expect it so no video, also no visual symptoms to report. Sound comes for sure from inside somewhere.