I have a 2-month old Nuova Oscar Simonelli that has served me well up till now. I would equalize pressure each time I switched it on, but I have never done a backflush. Now when I switch on the pump to pull a shot, the pump vibrates but quietly, and no water comes through.

I took the shower-screen off and there is a lot of crud back there. I hadn't realized how important backflushing is, I guess. It didn't occur to me that the release at the end of the shot, when switching the pump off, forces brew back through the system thus leading to an issue over time.

The machine is still under warranty (and Nuova Simonelli supplies no information about backflushing) but I'd prefer to fix this myself (it would be a month or two without my machine while waiting for them to fix it.)

My first question is, are my symptoms consistent with a crud build-up somewhere caused by not doing backflushes? Second question, how do I fix this??

I wonder if it's not simply an issue of the pump not being primed? The check valve for the reservoir gummed up? Check valve for the pump? Try taking a turkey baster filled with water to pressurize the pump while it operating. Pull the autofill wire so that there are fewer restrictions for the pump outlet, but take care that the boiler doesn't overfill.

With the autofill solenoid and group solenoid both open, and the pump pressurised with a baster or some other device, it should be easy to prime the pump.

I would first have a closer look at the check valve in the bottom of the reservoir.
I did a repair on one a couple weeks ago, so I have SOME familiarity with these machines but priming the pump is often an issue with ALL vibrator pump machines that aren't hook to a pressurised water supply.

Any comments welcomed

Norm

Sorry, I'm a bit of a newbie at all this (though mechanically minded) so I'm going to ask you to talk me through this more gently.

When I switch on the machine from cold the pump does prime - at least the pump comes on for a few seconds and I'm assuming it's priming. The pump noise is the normal 'loud' noise that does seem to signify that it is priming.

It is when the machine is hot and ready to pump water for the shot that the pump is all quiet as if it is choked (though even with the portafilter off) and no water - or sometimes a little water - comes through. Sometimes I could get it to start pumping (and the pump gets suddenly louder) by switching the pump on and off a few times - or even the whole machine - but lately even that doesn't do any good.

It does seem more able to pump water when the machine is colder, or when it is newly heated up, which leads me to think that thermal expansion in the valve is further hindering the valve movement. That's partly what got me thinking that the solenoid valve itself is getting stuck.

I am not sure how to take a turkey baster to pressurize the pump while it is running. Do you mean at the outlet from the reservoir or somewhere else?

I'm not sure what the autofill wire is, or how I would take care that the boiler doesn't overfill, so wasn't able to follow that part of your post, or the bit about the valve at the reservoir.

As for the autofill solenoid and the group solenoid both being open, I am not sure how to check for that, either.

Sorry! Maybe you could explain further? It would be much appreciated.

I just tried the machine again - and here are a couple more bits of information that might be useful.

Machine had been off for a while (an hour and a half). I switched the boiler on, and did NOT hear the pump come on as I think it normally should for a few seconds. Furthermore, the boiler is making 'boiling' sounds that I am not sure I have heard before when switched on from cold - is this normal? When I switched the pump on it pumped and water came through the group head. Normally I have found that the pump does pump water through, and is normal sounding, when the machine is cold or only warm - it's when it's fully heated that it won't pump water (with the accompanying choking sound).

So the distributor got back to me today - a week after I first contacted them! They think the pump needs to be replaced. Let's hope there's a service centre nearby, don't want to send the thing all the way back to Italy....