Nose Drip on Pre-Millennium Pavoni [Solved!]

[drgary]

Hi Folks:

I posted on the Refeathering the Peacock thread and got no response so am starting a new thread. Here's what I'm trying to solve. I've got a pre-Millennium La Pavoni Europiccola in great shape, except I've been unable to solve a nose drip at start-up. I've just serviced the group according to the old thread. The piston gaskets work well enough that when the machine cools and pressure inside the group decreases, the lever raises (lever erectus).

Here's how I serviced my machine. I removed the shower screen, portafilter gasket, piston gaskets; removed the old parts (white washer, brass ring with four holes, spring clip) from the top of the group. Removed the lever, top nuts, etc., cleaned everything in JoGlo, installed all new seals and washers, lubed everything with Dow111. I can't tell from the old thread and the Orphan Espresso video whether the white washer at the top of the group needs to be installed with the groove facing up or down. On the Refeathering thread the link to the photo no longer connects to an external site. When I opened it up, the groove was facing down and it vaguely appears that way on the Orphan Espresso instructions. So that's how I installed the white washer, but I doubt that's the issue. I did install the piston gaskets with the "V" facing down at the bottom and up at the top. This obviously makes them flare in both directions of the pull.

What might I be missing? The lever action is now very smooth. It makes good espresso, but that nose drip is pesky and I want to solve it. I'm not overdosing the coffee and doing multiple pumps, and it's just been serviced, so the seal isn't obstructed by coffee grounds. I actually opened up the machine yesterday and put more Dow111 in there. The nose drip decreased but didn't disappear and now it's back again.

[rpavlis]

Are you sure that the piston seals are pointed the correct way? The upper one needs to flare upward, and the lower one downward. If you have them both downward you will have the symptom you state. (The same will also true if the upper one be correctly placed but faulty. Basically the upper one keeps pressurised water from escaping from the reservoir, and the lower one keeps it from running back into the reservoir whilst the shot is being pulled.

[drgary (original poster)]

Yes. Thanks. I'm sure. (Of course memory's reconstructed and can err.) And the seals I just replaced were that way too. They were supple and also produced "lever erectus." This one's a head scratcher. But if no one else comes up with a better suggestion I'll pull it apart again and quadruple check that the seals are installed correctly.

[cyclocrossleverman]

Sounds like you have the piston seals pointed correctly. I've had minimal leaks on my machine in the past after re-lubing the piston seals. These were corrected when I re-worked them into the piston grooves with a dull probe like shown in Orphan Espresso's vid. I have a Millenium machine, and also developed a minimal leak that I resolved by tightening the inner teflon sleeve that had inadvertently loosened during a routine cleaning dissasembly. Don't know if that might be a factor in your situation?...

Re: the grooved white piston rod seal, I always have mine so that it faces downward towards the floor when installed. It seems to form a small recess so that the spring clip fits in a bit more snug than it would whilst fitting the spring clip in against the flat, non-grooved side. That's how I always try to keep it straight in my mind. I, like you, have not seen any distinct vid or diagram that shows this unequivocally.

[drgary (original poster)]

Thanks, Mike. On my pre-Millennium machine there is no Teflon sleeve. I've used the same logic as you for that white washer at the top of the group. If I hadn't been careful to install the piston seals Robert's diagnosis would fit. I've now got that OCD temptation to take it apart again and check, and that wouldn't be a bad thing. I'll mostly likely do that later today.

[homeburrero]

Sounds like you have all your gaskets right-side-up. Check this page for corroboration that the piston shaft gasket needs to be open-side down.

Your symptom points to a less than perfect seal of the upper piston gasket when the machine is cold and unpressurized. (I bet you already deduced that.) The leverus erectus would indicate that you have a tight lower seal when the machine is warm - as the boiler cools to a vacuum, atmospheric pressure is pushing up on that lower gasket, which flares and seals.

[drgary (original poster)]

Thanks, Pat. Francesco Ceccerelli comes through again. If my seals are facing the right direction, and I'll check later, then the only other thing I can conclude is that the cylinder is somehow off round or I might need to add some plumber's tape under the upper piston gasket as a shim. So whatever happens, I'll take it apart a third time. I may have just come up with the solution (plumber's tape).

[drgary (original poster)]

Never Underestimate the Value of a Good Shim

Thanks to Robert and Pat, I focused on the upper piston gasket as the culprit. My solution was to use 4 turns of Teflon tape on the upper gasket and two turns on the bottom gasket for a better seal. When I opened the machine, the piston gaskets had been installed properly, with the "V" facing up on top and down on the bottom. I suppose slight manufacturing variances of these seals and maybe my group cylinder made enough of a small difference that the seal wasn't holding. After the application of shims, I turned both switches on and allowed the machine to heat to full steam power, with the OPV releasing steam at full hiss and moan and the manometer reading over 1.0 bar or about 15 psi with no drips.