Thermosyphon Stall LaValentina

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erik82
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#1: Post by erik82 »

When warming up my LaValentina Levetta has a thermosyphon stall. It only heats to about 190F. When I turn on the pumps it sputters a bit and pushes out some air. After that I put a blindfilter in the group and flush. This trick helps to solve the problem and 15-20 minutes later the group temp is back to it's normal 203F. I hate this because my machine is on a timer and I want an espresso when I get home from work. The weird thing is that once in 3 times it doesn't have a thermosyphon stall. This is a thing of the last 2 months and before that it only stalled for about 1 in 10 times.

I've descaled the machine a month ago an pulled the mushroom out and all other parts of the group and descaled them. There wasn't much scale in there due to me using a waterfilter. I also took the OPV out and descaled it completely. The inner parts of the OPV where renewed about 6 months ago. So it shouldn't be a maintenance-issues.

When shutting the machine down I always empty the water tank and refill it the next morning when putting it on the timer. After cooling down for about 30 minutes there a couple of drops in the reservoir under the exhaust of the 3-way valve. the pressure of the machine is 9 bar tested and adjusted with my manometer portafilter.

I hope to have given you guys enough information to help me out with this problem. I just can't find out where the air is coming from. Could it be me emptying the tank pushing some air in the group when it turns on because of the water filter?

erik82 (original poster)
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#2: Post by erik82 (original poster) »

Tried to keep some water in the tank when shutting down but this makes no difference and LaValentina keeps stalling. After pulling a shot left LaValentina on for a couple of hours without pulling a shot and everything is fine.

Is there anyone who knows what might be wrong?

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HB
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#3: Post by HB »

For the benefit of those following this thread, the Levetta model has a regular E61 lever / valve:


La Valentina (left) and the Levetta (right)

In addition to the over-pressure valve leaking, the upper seal of the E61 failing is another possible cause of a thermosyphon stall; see Constant dripping from E61 grouphead for details. Stefano has a rebuild kit for the E61 grouphead: Grouphead Kit E-61. Finally, here's Randy's tutorial on Overhauling and Lubricating the E-61 Group.
Dan Kehn

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erics
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#4: Post by erics »

the upper seal of the E61 failing is another possible cause of a thermosyphon stall
That would get my first vote, i.e. replace the brew valve in its entirety and then inspect/rebuild your existing valve with the $3 valve face replacement, providing that the surface which meets the cam is satisfactory.

Use a mini-torch or hot air gun to soften the thread locker prior to attempting disassembly.
Skål,

Eric S.
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E-mail: erics at rcn dot com

erik82 (original poster)
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#5: Post by erik82 (original poster) »

Thanks for the tips. I renewed all the valves 4-6 months ago and they all look like new when I disassembled the group a couple of weeks ago so this shouldn't be the problem. If this was the problem the machine would also stall after a couple of hours idle, right? The surface which meets the upper cam is also clean and in good shape.

The exhaust isn't dripping the entire time, just a couple of drops during 30 minutes when I turn off the machine. When running idle it doesn't have a problem. I already found and read the topics you quoted and a lot more topics about this problem. After brewing the group releases its pressures with a big whoosh and after that only a couple of drops come out of the exhaust for the first couple of minutes.

These where the first things I checked and that's why I'm so surprised that the stall keeps coming. All parts in the grouphead are new or like new. I just can't figure out what could then be the problem.

I first thought that it was me emptying the water tank every evening and thus leaking some water out of the water filter. When I turn the machine on I thought that the first seconds it turns on the pump automatically before heating, that it would suck some air in the group because the water filter hadn't filled completely with water. After leaving some water in the tank for a couple of days and finding out that even then it stalled I gave up on this hypothesis.

Can there be a way that warming up using a towel around the group can cause air to enter the group because it is heating faster than normal? Just looking for some strange causes now because all of the usual stuff is ok.

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erics
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#6: Post by erics »

It is not a question of air getting in but that of hot water/steam getting out. The air which you likely introduce into the system when you empty the reservoir should be taken care of by the air release/priming valve attached to the vibration pump. I would discontinue that practice for a week or so as a trial.

As regards wrapping a towel around the group, I would discontinue that also because you are now (purposefully) inhibiting the heat transfer and perhaps overheating some sections of the group beyond design limitations.

Trace the path of water from the pump and see if there exists any hot section of piping on the pump side of the check valve.
Skål,

Eric S.
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E-mail: erics at rcn dot com

erik82 (original poster)
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#7: Post by erik82 (original poster) »

Thanks Eric, I'll try not using the towel and leaving some water in the tank for a couple of days to see if a stall will occur. Hope this fixes the problem.
Trace the path of water from the pump and see if there exists any hot section of piping on the pump side of the check valve.
I've traced the waterpath from the pump to the check valve and OPV, after a shot and a clear water blindflush, and there aren't any hot parts. Just a bit warm from the heating of the boiler but not brew water temperature.

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erics
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#8: Post by erics »

What I meant to say was "trace the path of water from the pump and see if there exists any hot section of piping on the pump side of the check valve while you are experiencing the thermosyphon stall ."

Keeping the reservoir at some reasonable level and avoiding the grouphead towel would not, by themselves, avoid a thermosyphon stall.

Can you give a time-frame as to when this stall surfaced? Like most other forum members, I read topics that arouse interest and I have seen lots of problems surface after preventative maintenance actions that were intended to avoid or minimize the chances of such problems.
Skål,

Eric S.
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E-mail: erics at rcn dot com

erik82 (original poster)
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#9: Post by erik82 (original poster) »

I now understand what you meant to say. I'll have a look the next couple of days and check the tubing if a stall occurs. Learned something new about the pump that it releases the air. Beginning to understand all the technique pretty well now. Most of it by reading a huge amount of topics on HB.

Yesterday turned the machine on while it was off for a couple of hours with water in the tank and no towel and it didn't stall. Have to see what the group temp is when I get home and it's on for an hour on timer. If it doesn't stall in the next 3 days with this method then I'm pretty certain that I've found the cause, how unlikely it would be that these measures would make a difference.

The stall surfaced in a time period when I didn't do any preventative measures to the machine. It began a month or 2 ago and I descaled a month ago. Prior to that the descale before was 10 months ago and the revision of the grouphead with new valves and seals was around 5 months ago. In the meanwhile I didn't make any changes. It just started out of the blue.

erik82 (original poster)
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#10: Post by erik82 (original poster) »

When I got home LaValentina stalled. Took off the case and had a look and feel inside. Attached a picture to my post with the red parts which where hot. The upper tube leading to the no-return valve was a bit hot but not really, but the silver colored connection was really hot (1 in the picture). Looking in the parts catalog of LaValentina it tells me that this is the 2-way Solenoid Valve 230V 1/8. Is it normal that this part is hot or should I take it out and try to clean and descale it? Could this be the problem?



Took everything apart to clean. Should the metal coloured part of the picture below come off? It is really stuck and I don't want to put to much force on it.


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