Thanks Martin, Ian, Marshall, and Randy.

First off, MY MACHINE IS WORKING NOW! I took all of your advice and started by pulling out the mushroom... As Marshall had noted, the interior chrome degrades. On the last descale, before the problem, I pulled the remaining chrome off. It looked pretty clean inside but I cleaned it up best I could including cleaning up the brew valve gasket etc.

One thing I had NEVER done was pull off the top part of the mushroom where the gicleur is. It was pretty scaled up and I let it sit in some solution, cleared the holes, and reassembled. My suspicion is that this might have been the area of the problem.

Ian recommended checking that the group wasn't leaking itself into the drip tray over time. All seemed o.k.

I also checked the OPV tube, as recommended by Martin, to make sure that there was not any flow out of it while the machine sat idle. It seemed to be stable. Anyhow, after letting my machine sit overnight, I was pleasantly surprised to find it this morning displaying 206F on Erics thermometer instead of 160F! The flow out of the group is back to normal now, hooray.

Thanks again, this site and the people that contribute to it, are such assets to this community.
cheers,
Kaelin

buzzmccowan wrote:... including cleaning up the brew valve gasket etc.

One thing I had NEVER done was pull off the top part of the mushroom where the gicleur is. It was pretty scaled up and I let it sit in some solution, cleared the holes, and reassembled. My suspicion is that this might have been the area of the problem.

Please to hear it has been solved!

However, whilst a clogged filter and gicleur in the top of the group would not help with pulling shots, that should not contribute to the thermosyphon stalling, see http://coffeetime.wikidot.com/the...e61-group-mushroom

It is much more likely that cleaning the brew valve solved it. It is also possible that a small amount of water could let by the brew valve without the group "dripping", since it is hot enough and slow enough to just evaporate.

All the best,

Martin

Did you descale the heat exchanger or just the boiler? Sometimes folks forget that they are two independent systems. Descaling one will not take care of the other. If you gicleur was scaled up, I would say the inside of your heat exchanger is the same since they are part of the same hydraulic circuit. You can see how the typical heat exchanger works from this hydraulics diagram that Eric S did.

cannonfodder wrote:Did you descale the heat exchanger or just the boiler? Sometimes folks forget that they are two independent systems. Descaleing one will not take care of the other. If you Gicleur was scaled up, I would say the inside of your heat exchanger is the same since they are part of the same hydraulic circuit. You can see how the typical heat exchanger works from this hydraulics diagram that Eric S did.

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I ran the original descale on both the boiler and HX. I also ran a series of blind flushes after the descale, however, I ran a couple of much longer blind flushes which might have cleared some obstruction in the OPV.

Not sure what was wrong, probably the brew valve, but I was able to enjoy some El Salvador Matalapa peaberry this morning that I roasted last week. Thanks,
Kaelin

cannonfodder wrote:You can see how the typical heat exchanger works from this hydraulics diagram that Eric S did.

The diagram is specific to Quickmill, not Vibiemme. In prinicpal it's the same. Specifically the OPV is in a different location on the Vibiemme.

I knew if I bitched enough, you'd draw one. Thanks!

I thought that most Vibiemmes have a Thermosyphon restricter to prevent the grouphead overheating. Would that not have explained the symptoms?

andy_P wrote:I thought that most Vibiemmes have a Thermosyphon restricter to prevent the grouphead overheating. Would that not have explained the symptoms?

No. Restrictors do reduce the group temperature and slow recovery time (relative to an unrestricted thermosyphon), but the symptoms were more severe than this: 160F is just too low measured at the point Eric's device sits. The poster had stated that normal idle temperature was 208F. An unrestricted group might sit at just above 212F on an HX machine.

A blockage could describe the symptoms. However, the poster said that it took longer for water to appear at the group after the machine had been idle for a while than it did before, which indicates that the is HX losing water (due to small leaks, probably the brew valve in this case). When too much is lost, the thermosyphon can suffer or stall completely. The group is then heated by a vastly reduced thermosyphon flow, or purely by conduction through the very hot pipes!

Hello all,
Thought I'd dredge up an old post I created. The same problem started again a week or so ago. What is interesting is that on Eric's grouphead thermometer the temperature would go up to 200F and back down to 150F periodically. I am assuming that the air was in the group during the lower temps and water cycling back in at the higher temps. The long and short of it is, I took apart the OPV last night and there was some build up of scale around the plunger. After a scraping and clean, and leaving my machine overnight, the group seems stable again. Thanks to everyone who helped me originally.
Cheers,
Kaelin