Hello,

my oscar power is most of the time on, and me and my family are making coffee drinks constantly. I noticed that hot steam is constantly emerging out from the oscar 1st release tube into the drip tray. If you are looking into the brew head this tube is located to your left.

Besides of the non stop hot steam release, when we brew espresso, this tube release a lot of water and not only the small amount of water which is extra in the brew process.

If we do not brew espresso for a while, the constant release of steam, dries out the whole heat exchange tube( e.g.the tube that goes inside the boiler to the brew head). If brewing is needed after a while, the pump has to work about 15 sec to fill up this heat exchange tube, and very hot steamy water is going out from it through the brew head. the coffee powder is burned.

Thanks you all for replies!

I don't know anything about this machine in particular, but if the HX is open to the exhaust tube, then you've got a 3-way valve issue. That you can still brew without pumping all your brew water through the exhaust means that it is partially functioning.

Do you ever do detergent backflushes? If not, you might try running a few cycles of backflush and see how that goes.

And it sounds like you need a flush routine before locking the portafilter if you're brewing too hot.

Good luck!

Hi, Joe!

Is it something like this?



Anyway, considering your description, it seems you have some trouble with the neplax valve, that's the left one at the group head, looking to front of the machine. It seems air entering the HX by this connection. In your case, could be the valve opening low pressure and so steam get out and air get in. I was getting this behavior with poor sealing at the neplax valve connection.

As the neplax valve is not expensive, you could try to replace it first. As far as I know, the newer valves are rated 16 bar, so it won't open even during the shot anymore. It's more a safety valve for the HX. If you want lower pressure to brew (9 bar for instance) you'll have to add an adjustable OPV before the HX (right after the pump) and divert the water to the tank. Another great mod are the restrictors they use at Musica, there is some here:

Nuova Simonelli Oscar restoration

Márcio.

Huh, that's an interesting configuration.

Is it something like the valve in the fill manifold on my Faema C85 which occasionally dribbles water? I can see an overpressure on the HX would be a good thing, just never puzzled it out before.

the oscar has valve located near the boiler. this valve has electrical switching.the switching control the way of water from the cold water tank to boiler or heat exchange path. i am suspecting this valve but i canot think about scenario that this valve cas cause my problems.

Thanks!
i will buy new neplax valve.

considering your you tube, it is not like this. i have to wait 10 sec, pump is working and only than steamy water goes out.

Carneiro wrote:Hi, Joe!

Is it something like this?



Anyway, considering your description, it seems you have some trouble with the neplax valve, that's the left one at the group head, looking to front of the machine. It seems air entering the HX by this connection. In your case, could be the valve opening low pressure and so steam get out and air get in. I was getting this behavior with poor sealing at the neplax valve connection.

As the neplax valve is not expensive, you could try to replace it first. As far as I know, the newer valves are rated 16 bar, so it won't open even during the shot anymore. It's more a safety valve for the HX. If you want lower pressure to brew (9 bar for instance) you'll have to add an adjustable OPV before the HX (right after the pump) and divert the water to the tank. Another great mod are the restrictors they use at Musica, there is some here:

Nuova Simonelli Oscar restoration

Márcio.

Thanks! i will buy new neplax valve.

That might be the easiest solution. The valve in question is in the pic below and is labeled "expansion valve".



I would think that all are adjustable; some readily, some not so. In any event I believe the Nuovo Simonelli intentions behind this part are that it act as a thermal expansion valve/safety valve for really excessive hx pressures during brewing or due to thermal expansion of the water contained therein when idle.

Given your description of events, replacement would be the best route but I would still disassemble the patient and do an autopsy.

Thank you!

does the valve, with the solenoid, e.g opposite to the neplax valve, has to drain water while brewing is in progress? this is what happening now. i assumed the the pressure release and water drain will happend when brew is finished, controlled by the central command unit, which open the valve in time.

The brew solenoid valve needs to be soaked in white vinegar or a citric acid descaling solution. Remove the coil and unscrew the valve housing. The valve seat housing can remain as is.

There should be no leakage while brewing and lots after brewing ends. See here for a nice description of 3-way valve operation: http://www.frcndigital.com/coffee/3way/intro.html

And here You can find a tips and tricks-section for Oscar -and a 5 photos series for 3-way valve cleaning -on box titled: It is probably blocked the 3-way valve. http://www.elektros.it/tips_and_tricks_en.html