Pavoni gone sour

[EnPlusOne]

I'm at a bit of a loss here.
I've been using my La Pavoni Europiccola now for over 12 months getting some of the best coffee i've ever had out of it and all of a sudden things have gone sour.
The beans i was using when it first happened were getting slightly out of date (20 days post roast) so i ditched them and got a fresh bag, no good. I then tightened and loosened my grind compensating for extraction time with pressure applied during extraction and tamp pressure. Still no good. I then thought that maybe somehow the pressure stat had somehow backed itself out and had caused a drop in temp. While the shot has now darkened slightly it still has a sour taste. My machine doesn't have a pressure gauge fitted so i'm not sure exactly what i'm getting out of it now but i'm guessing it is now slightly too hot.


Where to now? any help would be greatly appreciated.

[shortblackman]

It might be due for a new piston seal. I bought an LP new, and after 18 months is solid use it was getting worn. So if yours is second hand, or if you've been using it a lot this might be the problem. Pretty simple machines. Not a lot to go wrong.

[EnPlusOne]

Thanks SBM. I did a rebuild on it less than 2 months ago. It was working better than ever post rebuild. Nothing really changed when the flavour did. Lever still feels like it should and the machine still makes all the right noises when pulling the lever up and filling the group. The shot even pulls like it should the only thing that has changed is the crema is a little thinner and the taste is bordreing on undrinkable. It's got me buggered.

[Yelta]

If it were me I'd pull it apart again and give it a good clean, I assume the water tank is clean?

As SBM says, they are a simple machine, shouldn't be a major problem to sort out.

[shortblackman]

Could something have dislodged - relodged after your work, causing an irregular flow?
The hot temperature thing is funny. That would usually result in thin crema (which you describe) and bitterness.
Sourness is often associated with under extraction/ cold temperature, isn't it?
Could you pull it apart & see of anything shifted in your rebuild as Yelta suggests?

[EnPlusOne]

Thanks for the help guys.


It started off being too cold so i adjusted the temp stat up to the point where the shot became really dark/ thin crema. I then bought the temp back down gradually and this seems to have fixed the problem.


I had ruled out pulling anything apart because i hadn't noticed any change in the way the machine was operating. The only change was to the taste.


So i'm still stumped as to what was causing the problem but i'm back to pulling the tastiness i was used to.


Cheers

[Yelta]

Perhaps an act of god.