Hi, since a few weeks I own a Gaggia Classic. When I bought it second hand, it all seemed fine. However, I have difficulties with pulling a decent espresso shot. The main problem is that when I grind my beans relatively fine (but I don't think too fine), the pump has difficulties with pressing the water through. I see / hear also a water flow back into the water tank and the coffee running very slow out of the PF (and not a good color). My main question is, is it normal that water flows back into the water tank? I can grind them more coarse, but then the coffee is just to waterish / no good taste.

Things I did so far:
The OPV seems to work properly, as I've backflushed it yesterday (for the first time) using Cafiza. I've descaled it last week with some espresso machine descaler. I've cleaned the group head by taking it apart, and as expected it was quite dirty as I believe it has never been cleaned properly. I replaced the group gasket with a new one. Lastly, I ordered a manometer which should be delivered this week, so I can check the pumps pressure.

I'm running a bit out of options, so I'm thinking about taking it all apart, cleaning everything. As I read many posts here and on other forums I suspect some scale blocking the main valve. Could that be it? Any other suggestions I can try or should focus on?

Update: I now also measured the water flow out of the group (without PF), and it's about 550 ml/min. I read somewhere here on H-B that it should be around 650ml/min for the Classic.

Thanks a lot!
Igor

Honestly, Igor, the best thing to do for a second hand Gaggia that gives you even a bit of trouble is to open the boiler and do a thorough examination. There is no telling what is lurking in there.

The water flowing back to the tank may well be a result of the OPV (over pressure valve) being either set too low or being clogged. If -- as you say -- the group head was quite dirty, there is no reason to believe that what you can't see is any cleaner. You could certainly open up the OPV and give it an adjustment and see if that helps, but my guess is that you have more scale build up inside than a simple descaling will get rid of.

You know, you haven't mentioned what grinder you are using. The flow of water that you are getting doesn't sound unreasonable, so it is very possible that your grinder is simply not up to the job of producing the fineness and (even more importantly) the consistency of grind that you need.

odyon wrote:is it normal that water flows back into the water tank?

Yup! That's the OPV doing its job.

odyon wrote:The OPV seems to work properly, as I've backflushed it yesterday (for the first time) using Cafiza.

I suspect you mean the 3-way solenoid here. You're talking about the "pssssht" splash of water after ending a shot, yeah?

UltramaticOrange wrote:I suspect you mean the 3-way solenoid here. You're talking about the "pssssht" splash of water after ending a shot, yeah?

Aaah, thanks UltramaticOrange! That explains some more to me now for me, regarding the difference between the OPV and the 3-way solenoid (maken that pssssht sound, exactly ). So, if I'm correct, while building up pressure, the OPV makes sure the boiler won't explode (if pressure becomes to much, it will feed water back into the water tank), and this is the valve that's adjusted by people to get the exact right pressure? And the 3 way-valve only does it's thing, as soon as you switch the pump off, to get the pressure of the PF and don't have coffee all over your kitchen walls (as I head sometimes before with my Saeco )?

@SJM: sorry, I forgot to mention. I bought a Nemox Lux. My budget was not that big and so I was doubting between the Gaggia MDF, the Lux and some others. However, I chose for the Lux, because of several relatively positive reviews (taking into account it price), as well as the possibility for making it step-less.

The OPV is keeping the the pressure at 9 bar (assuming your machine is calibrated correctly) during the shot. I'm assuming that water is only flowing back into the tank while pulling a shot (pump is active), correct? If it's putting water back into the tank at any other time, there's something wrong happening with the machine.

@UltramaticOrange: exactly, only when I start brewing the water starts flowing back.

I just finished my portafilter with 0-16bar manometer at the end. I checked the pressure (the way it's described elsewhere), and the needle is moving a lot. But I think the pressure is between 9 and 10 bar. That should be good, right? Is it weird that the needle moves a lot (between 8 and 11 bar, was a bit difficult to see it exactly)? Or can it be explained by the OPV not working nicely?

Any other suggestion I can check? Or is it time to open up the whole machine / clean out the OPV / etc?

Is the gauge you are using liquid filled?
If not, that explains the fluctuations of the needle.

When we give directions for building a pressure gauge, they include sourcing a liquid filled gauge.
If yours is at least bouncing around the 9-10 and that is enough information for you, you can just accept it.
If not, you should upgrade to a fluid-filled gauge for accuracy.