Hi All,
I wonder if someone could help me with this issue.

I've serviced a couple of La Pavoni Europiccolas now, although i'm no expert, however I now have the wonderful brass/copper La Pavoni Professional 2011 model with the lovely wooden handles.

Having replaced the Grouphead gaskets and the Teflon sleeve, which by the way was a nightmare to tighten, until I used some silicone grease; I now get water coming out of the group's shower head screen as soon as the Pressure reaches around .75- .8 bar with the lever in the proper down position!
The water boils as usual, with some dripping from the OPV as I would expect, and also a bit of steam rising from the OPV, which is also normal I believe. The water dripping from the shower screen lasts about a minute and then settles down once the pressure variance does and it has expelled about 90ml of water out of the shower head. So the water does eventually stop dripping so you can still make a normal great cup of coffee and steam is fine.

The manometer needle pressure does rise, after boiling point, from anywhere between the half way mark between the .5 and 1 bar manometer markings, and then goes upto I suppose about .85 bar. What I specifically notice, importantly, is that it's the initial meteoric rise at from the half way manometer markings between .5 and 1 bar, only after boiling point, that the dripping suddenly begins.

The pressure reading is about .7 bar when the initial boiling phase settles down, which I assume to be right although I gather the manometers are notoriously inaccurate.
I have played around with the Thermostatic screw from right-in to about 2.5 turns out, with the difference being it seems to make some difference to how much water is in the machine as to how much it leaks. In addition I get no crema with the screw out and good crema with it screwed in. Naturally I never overfill the boiler, I always fill to under at least 1cm below the top of the water gauge. But even if the water gauge reads half full , this problem still happens. As background I had to use silicone grease around the thread of the sleeve in order to tighten it to the right depth. I also used, as apparently one should and I have had no problem on Europiccola, some silicone grease on the gaskets around the brass piston. I'm pretty sure the sleeve is not cracked either.

The only other thing I wonder is if the OPV is perhaps not working as it should or somehow, or maybe water is entering the sleeve at some undesirable pressure point, which would then point at the Thermostat being the culprit. There is no leaking I can see anywhere else.

Has anyone experienced this before and do you know what causes it? Are there any tests to prove or disprove the thermostat or OPV could be the causes?

You should never be getting steam release from the over pressure valve in normal operation with pressurestat equipped La Pavoni machines. Late ones, like you have, normally have a vacuum relief valve, but that should close as soon as the vapour pressure of water in the reservoir reaches atmospheric pressure.

Are the piston seals on correctly? Are you sure they have not been damaged? This model should have a brass piston. Are you sure that the polyphenylene sulphide cylinder liner has not been damaged? Since this is a "Professional" it has a pressure gauge. It is probably best to have the pressurestat set to a bit under 1.0 bar (100 kPa). Are you sure the pressure gauge is reading correctly? You can attach some other type of gauge to the steam tube to check it. (I have used Presta valve bicycle tyre pressure gauges for this.)

Sometimes the overpressure valve gets stuck open due to scale. This can be temporarily addressed with a strong tap to the nut in the middle of the valve.

The plastic sleeve could be damaged. When these are turned in, the slot does not align vertically or horizontally. It's not a user-friendly design for servicing. Turning it too hard could have cracked it.

Piston gaskets should be installed this way on these machines. Imagine this being vertical: >< . In other words, the gaskets should be arranged so the cup faces down at the bottom and up at the top. This presses water down through the coffee cake and up above the piston.

How about popping the shower screen off and with the piston properly positioned, fill up the boiler to the proper level, turn it on and watch whether the dripping is coming from the piston/sleeve side or outside the sleeve/grouphead side? While it's routine to lube the upper sleeve gasket, I've also applied a small amount on the grouphead side threads and gasket seat. If the sleeve isn't cracked or deformed and a leak is determined to be between the sleeve and grouphead, a simple/inexpensive solutiion is to wrap a couple of turns of Teflon tape to the threads and reinstall.

Thanks drGary and GodShots
I thought I would try the OPV first and disassemble to see the state of play.
There was no real limescale to speak of, certainly nothing to worry about or cause a sticky valve.
So I cleaned it up and reassembled.

I've just switched it on again and I'm still getting the dripping as before from the shower.

SO now its plan B and I'll try GodSHots's plan to try and spot the location of the leak.
Where should water be coming from and when since there is that actual tiny hole in the Teflon sleeve? Which i think is the inlet valve for the hot water once the piston rises above it.

Any clues on what I should see?
Gonna have to lose the already quite new filter gasket as the only way i can get them out is using a screw inserting it into the rubber deep and then pulling it hard with pliers and removing it.

BTW drGary yes I definitely put the piston ring gaskets the right way, however maybe I shouldn't have used so much grease, could the grease enable an escape for the water?

I've had a think about this and given the machine one it stops dripping, when the pressure settles, it makes a perfect cup of coffee. It then does not leak as I said before. So that would lead me to conclude there can be no crack in the teflon sleeve or the dripping would not stop.

So could it be a thermostat issue or still the OPV? I don't think its the thermostat as the temperature is about right for the coffee and the steam wand is functioning perfectly,so that would lead me to think why is the Group head serving as the OPV rather than the OPV?

You do not need to destroy the dispersion screen to portafilter gasket to get it out. You can remove the group from the machine, remove the handle, and put the nut back on the threaded rod that holds the piston to prevent damaging threads. Now just take the group, turn it over and press it against a piece of wood. The dispersion screen should pop right out. (You can also remove the nut, and without a portafilter inplace, pull down on the handle a bit. This should loosen the gasket so that it should push out with less force.)

Does the water come out from inside the sleeve or around it (more likely)?
Looking at this diagram
http://www.linz.wright.name/pavoni/Pavo ... ection.png
I would be concerned about the sleeve rubber seal or maybe a crack in the sleeve that tightens as the temperature goes up.

I think it might be necessary to take the group apart and examine the sleeve.

Thanks for the advice chaps.
I'll take the group apart.
If only mine was as easy to disassemble as yours, My gasket is too tight now to push out that way as I was able to very soon after fitting it, do it your way, but now the gasket is stuck fast! I might try penetration fluid first just in case that works.
Will check the sleeve by removing it!
Thanks for suggestions guys.

Try using a dental pick. The tip looks like a '7'. Slip the tip in tangentially along the outer edge of the gasket. Turn 90 degrees to place the tip under the gasket. Pull down gently. Mine comes off quite easily.

ochapple wrote:Thanks for the advice chaps.
I'll take the group apart.
If only mine was as easy to disassemble as yours, My gasket is too tight now to push out that way as I was able to very soon after fitting it, do it your way, but now the gasket is stuck fast! I might try penetration fluid first just in case that works.
Will check the sleeve by removing it!
Thanks for suggestions guys.

Do not use "penetration fluid," by which you probably mean penetration oil, which smells similar to machine oil and will leave you with a nasty cleaning project. A pick really does work if you gently insert it under the portafilter gasket.