Could there be something clogging the line b/w your boiler and the grouphead? It sounds like everything else in is order. Are you sure your lever is all the way up in the up position?

There's plenty of pressure without coffee in the pf, so the boiler's pressure valve probably isn't the problem. I just took the group apart again and cleaned out the water inlet holes with a q-tip and compressed air. The problem persists, so I guess I'm back to the piston seals. In the worst case, replacing them will tighten up the resistance on pulls, and if I'm lucky it may somehow fix this issue too (maybe the seals are partially occluding the water inlet holes or something). Thanks again for the help, and I'll report back once I get the new seals (will probably be a couple weeks, since I'm heading home for the holidays).

Please do not take offense, but is the actually lever on the "correct" way?


I only ask, because in this picture (if you click on it, it will enlarge) the handle is on upside down.

Yes, the lever's on correctly, and no offense taken I was mindful of that possibility from reading the "refeathering the peacock" thread. If only that had been the problem; it would have been a very simple fix!

Update: My fix of using plumber's tape to try to prevent the nylon piston from slipping seems to be a failure. This morning my pre-infusion failed. When I took the group apart, as expected, I found that the piston had rotated enough to prevent the water from entering the chamber with the lever in the up position.

I tightened it and put the thing back to together and the peacock is good to go again.