Nuova Simonelli Oscar pulsing steam

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dlemon

#1: Post by dlemon » Dec 03, 2013, 4:21 am

My Oscar developed a sudden problem. After searching the forum my problem was similar to this post:
Nuova Simonelli Oscar with brewing trouble Nuova Simonelli Oscar with brewing trouble

So I replaced the retention valve on the left side of the boiler
Image

The valve was definitely trashed and needed to be replaced. Unfortunately, there was no change in the problem.
So in my estimation either:
* I totally screwed up in the new valve during the install, or
* There is something else up next to be replaced

I saw one member mention there is the same retention valve in the steam valve assembly. I don't know if the valve there could be the source of the problem.

Either way, there continues to be steam pockets, a momentary stop of water flow, more steam, before getting an even dispersion.

Any ideas where to look next?

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Carneiro
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#2: Post by Carneiro » Dec 03, 2013, 5:40 am

When I restored two Oscar I had this problem with the first one. I think it was some small leaking at the brew (HX) connections and maybe it was sucking air whenever the machine went cold. I suggest you do the Musica restrictors mod and at the same time revise the connections. The temperature profile and management with the restrictors are very nice.

dlemon

#3: Post by dlemon » Dec 03, 2013, 9:20 pm

Thanks Márcio! I saw your mods before, didn't realize you had the same problem on one of the machines before add the restrictors. I've been trying to save up the cash to do a bunch of mods at once, though the Musica restrictors are obviously cheap. In addition to the restrictors, wanted to add a cold water side adjustable opv, vacuum breaker, and least important but convenient and expensive mod of converting the steam knob to a lever.

Back to the point. I leave my Oscar on 24/7 (until I get that vacuum breaker and a timer). So it stays hot. Not sure if that means anything to the advice you given regarding the machine going cold. Still possible though I suppose.

I may have to just go ahead try the restrictor mod for now and forgo on the other mods for now. Hopefully it will solve the problem and at that same time have an improved machine. I love my Oscar, but man she's needed a lot of TLC since getting second hand.

caeffe

#4: Post by caeffe » Dec 04, 2013, 2:32 am

I too have the same problem. Steam out of group head, followed by water, then steam, then water. The behavior is inconsistent.

My previous search here indicated that some folks replaced/descaled/refurbed the neplax valve (#11 on the oscar hyd schematic http://nuovasimonelliusa.com/images/Tec ... iagram.pdf). I don't quite understand how this valve could be the reason since its function is to protect the hx from over-pressure.
Other searches indicated possibly the 3 way valve (#10) or the 2 way valve. I was going to ask this on a separate thread - what are the functions of the 2 way and the 3 way valve?

I'm like the OP - what else could be causing this?
LMWDP #162

dlemon

#5: Post by dlemon » Dec 04, 2013, 11:45 pm

caeffe wrote: Other searches indicated possibly the 3 way valve (#10) or the 2 way valve. I was going to ask this on a separate thread - what are the functions of the 2 way and the 3 way valve?
Here is an excellent resource describing the how a 3 way valve works from espressomyespresso.com
3-Way Valve Hows and Whys
How a Pressure Relief Valve Works

I am not an expert here at all. But I would say that anywhere there is a connection there is the possibility of air siphoning in. Same with any of the seals in the valves.

I replaced that neplax valve about two months ago. The original was dumping water into the drip tray like crazy. I've never replaced the 3 way on this machine, so I can only assume it is the original. It doesn't "seem" to be malfunctioning. I probably need to find out how to test it completely.

I took both valves off last night, just to see if re-seating them may solve anything. Gave them both a bath in citric acid for good measure, though neither really needed it, I had just descaled about 3 weeks ago. Re-installed them both and still have the same problem. Time to move to the hx connections I suppose into the group head. When I do that, I will do Márcio's suggestion of doing the music restrictor mod.

At least for now, if I do a long flush, I can make some passable shots. The mods may have to wait til after the holidays. Too much traveling! Which usually means I get to explore some new cafes in between the bad coffee stops.

I'm open to suggestions, I was so sure it was the retention valve after seeing it in pieces. Thought...Could I have completely destroyed it during the install? Maybe I should open that valve up again, just to check.

Still trying to figure it out...

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Carneiro
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#6: Post by Carneiro » Dec 05, 2013, 4:26 am

You can smash the retention valve if you go too far with the male connection... They use some thread locker at factory, I've used PTFE tape, a little bit "too much" so the thread was firm with 3-4 turns.

Márcio.

caeffe

#7: Post by caeffe » Dec 05, 2013, 8:17 pm

dlemon wrote:......
I am not an expert here at all. But I would say that anywhere there is a connection there is the possibility of air siphoning in. Same with any of the seals in the valves.

I replaced that neplax valve about two months ago. The original was dumping water into the drip tray like crazy. I've never replaced the 3 way on this machine, so I can only assume it is the original. It doesn't "seem" to be malfunctioning. I probably need to find out how to test it completely.

I took both valves off last night, just to see if re-seating them may solve anything. ......
Still trying to figure it out...
In my opinion, i doubt it is the neplax valve as that valve is downstream of the group head and it seems to me the behavior of it dumping more water into the drip tray means it is set to a low pressure - my understanding is that this valve is to relieve backpressure on the line, protecting the hx line from >15 bar. I've set mine so that it dumps water at ~ 10bar or so.

The check valve (or retention valve) you replaced may have been a contributor as well as the 3 and 2 way valve. The other check valve by the steam wand but again that appears to be out of the flow from the grouphead. I took my 3 way valve off but was unable to disassemble it completely and merely soaked it in citric acid. Things improved a bit but i still get the pulsing steam flow. I'll check the 2 way valve next - have to wait till this weekend though

I've been wanting to do the musica restrictor mod but I'm hesitant since it involves cutting threads/holes into the group head - if I had an extra group head lying around I'd love to do the mod.

Keep us up to date and I'll also let you know my progress.
LMWDP #162

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plindy

#8: Post by plindy » Dec 06, 2013, 8:07 am

helpful references
look

look for small parts of plastic valve inside the 3 way
you can loosen the tower portion of the 3 way while the base is still attached to the group head. The plunger should move freely in the tower, there are 2 spring loaded seals on the plunger, one on either end, they should move freely within the plunger.

The neplex valve is a spring loaded seal set to open at 16 bar. My understanding of it's function is that if during the brew cycle the coffee gives over 16 bar resistance it opens, when the pressure falls below 16 bar it closes.

The group head, HX, hx inlet and return, and the neplex are all connected to the normally closed port 2 of the 3 way. A small part of the broken valve any where in these components can cause pulsing.

During the brew cycle the 3 way plunger moves to open both port 1 and 2, and closes the exhaust port. Water goes from all of the above, to the breaker plate, shower screen, and coffee.

End of brew cycle, the plunger in the 3 way closes port 2, opens the exhaust port, vacuum pulls the water up thru the screen, breaker, thru port 1 around the plunger and out the exhaust of the 3 way to the drip tray.

G'luck

caeffe

#9: Post by caeffe » Dec 07, 2013, 1:31 pm

Loosening the 3way whether attached to the group head or not is a pita.
I'm going to just try flowing citric acid through the system and see if that helps

If steam is the only thing coming out of the group where is the water being pumped going? I don't see any water in the drip tray so its not coming thru the 3way or the neplax isn't it?
LMWDP #162

dlemon

#10: Post by dlemon » Dec 09, 2013, 3:31 am

Márcio you were right! Checked the valve last night. I had used pipe joint compound which let me tightened it down too tight crushing the new retention valve. Still somewhat usable I re-installed it temporarily, this time with PTFE tape, until the next one arrives. I'll have to fix it after the new year with much traveling going these next few weeks, I won't be needing Oscar for a while. With some long flushes I'll continue to get some passable shots in the mean time.

Hopefully, after getting the new retention valve and installing it correctly with some PTFE tape it will take care of this latest issue once and for all. Then I can work on some of the other mods.
- Daran