La Pavoni problem - lever resistance too high after servicing

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ab1289

#1: Post by ab1289 »

Hello,

After a couple of years of great coffee my La Pavoni Professional (2020) started leaking around the group head. I decided it was a good time to service the machine so bought a kit from the Espresso Shop and followed a YouTube video that explained how to replace the gaskets, lubricate etc.

Since servicing it I have tried making coffee with beans from the same company I had previously been using, dosing the same amount (14.5g) and using the same espresso setting on my Niche Zero that produced good results before.

When the machine is off the lever feels slightly stiffer than before but not crazy resistant (ie I can move it up and down with a couple of fingers). When the machine is on however and I try to pull a shot it chokes and I can't pull the lever down. I tried grinding much coarser (filter setting) and with considerable effort I can pull a shot but it tastes awful.

After checking forums someone had a similar issue and said that silicon piston gaskets with a bit of Molycote 111 helped them. I tried this and it hasn't fixed the problem.

Any help / ideas of how to fix this would be most appreciated! I assume that I need to make some adjustments so that I can return to a finer grind but not sure what to do.

Many thanks,
Adam

ojt

#2: Post by ojt »

We may need a little bit more information to be able to help. Here are a few of questions to get started.

So, if the problem is pulling the shot then I assume that water is entering the grouphead, which is good. I also assume you cleaned the showerscreen so there shouldn't be any obstructions. Is the flow from the screen good if you make a flush when the machine is hot?

What all did you do? Changed gaskets and lubed them with Molykote/Dow 111? Did you take the sleeve off by any chance?

Do you have a grouphead thermometer? Is the boiler pressure still the same, for example 0.8 or 1.0 or so.

I'm just thinking that, the machine being as simple as it is, unless the grind or the temperature change there shouldn't be a massive difference in force needed to pull the shot.

Edit: Oh, of course a different coffee would require a different grind. Perhaps a much fresher roast and easier to extract in general, or one that tends to grind into loads of fines (looking at you Ethiopian beans).

Hopefully we can get to a solution here.
Osku

ab1289 (original poster)

#3: Post by ab1289 (original poster) »

Hi Oksu,

Thanks for your reply!

Yes, water is entering the group head, I cleaned the shower screen so should be ok. When the machine is hot the flow seems ok (maybe was a bit stronger before but hard to tell).

I didn't take the sleeve off, I changed the gaskets, added lubricant, changed few clips. This is the kit that I bought (although I didn't use a couple of the gaskets e.g. I didn't remove the base of the machine): https://www.theespressoshop.co.uk/Mobil ... -2256.aspx

I have a group head thermometer strip and do the same method as before (i.e. flush some water through group until it reaches 85 degrees, and then remove air in steam wand before pulling a shot).

The boiler pressure reaches 0.8 bar as before. The beans are same brand and roaster as before, Brazilian beans roasted for espresso, roast date ~ 2 weeks prior.

Appreciate your questions and any help!

Best wishes,
Adam

ziptie

#4: Post by ziptie »

Were you measuring output prior to the overhaul? I am wondering if there wasn't some leak-by with the old piston gaskets that was resulting in less resistance. Granted, this is odd though.

One other thing to try (in addition to the coarser grind) is to down-dose until resistance is more reasonable...maybe 10 or 12g.
That said, it does sound like something with the reassembly is wonky.

baldheadracing
Team HB

#5: Post by baldheadracing »

As a wild guess - the piston gasket(s) were installed upside down - or the lip of a piston gasket folded over when the piston was installed back into the cylinder.

Good luck!
-"Good quality brings happiness as you use it" - Nobuho Miya, Kamasada

ab1289 (original poster)

#6: Post by ab1289 (original poster) »

Hello,

Thanks for the replies, appreciate all the suggestions.

Prior to servicing it was 14.5g in and about 28g out. I have tried grinding coarser and whilst it will pull easily again the coffee no longer tastes good. I also tried 12g and it didn't seem to help. Agree maybe something was wonky when I reassembled it, no idea what, if I can't figure it out from suggestions on this forum I may have to pay for a professional service and admit defeat :(

I checked the piston gaskets were the right way up, good point about whether the lip folded over when inserting it back into the cylinder, I'll check that tomorrow. Given that I tried with 2 new sets of piston gaskets I suspect it's unlikely that happened on both occasions but maybe!

Many thanks,
Adam

ojt

#7: Post by ojt »

Slightly off topic suggestion, don't flush to heat the group. The grouphead might actually heat up more than you intended and you're wasting brew water :) On your machine you can just "dry pump". Pump the lever up and down, but only until no water comes out. This circulates water between the group and the boiler.

As for the issue, I still think it isn't a mechanical one. I just can't think of anything that would behave that way. If there is water in the grouphead, the piston moves, showerscreen is clean then you should be making coffee like before. The problem should be below the showerscreen. Grind, coffee, basket. Or in temperature.

If the piston gaskets were wrong for example, you'd either have leaking or very little water coming out when pulling (and likely little resistance), depending on how the gaskets were put in.
Osku

mborkow
Supporter ♡

#8: Post by mborkow »

Lever arm installed upside down maybe?

ziptie

#9: Post by ziptie » replying to mborkow »

That would not effect lever fluidity. Although it would result in lower potential volume output.

User avatar
Kaffee Bitte

#10: Post by Kaffee Bitte »

I am surprised you didn't need to change the sleeve o-ring, since that is usually the root of leaking from the group. That and repositioning the sleeve wrong can lead to some odd lever problems. But since you didn't it is most likely baldheadracing's idea about the gaskets. It could also be that your piston head has loosened and is spinning. This can cause all kinds of weird effects downstream. The last one is rare now with the metal pistons but they can come unscrewed too. Usually it will be during gasket change and cleaning that you might have slightly unthreaded it, and now in use the piston is spinning more loose during the pull.

Edit. One thing I have noticed on my 3rd gen pro, is the lever has more side to side play than my Stradivari. This sometimes gets me when not paying attention to how the lever is positioned during pull. I have had it off to one side too much during pull and it made it much more difficult to pull. Once I noticed and corrected it eased to a better pull.
Lynn G.
LMWDP # 110
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