I'm starting to think you are right Randy. Maybe i should just stop worrying and brew some more espresso.

I do like to get to the bottom of things though i an really appreciate being able to rely on the more techy guys and girls or this forum for ideas and suggestions!

Like i mentioned earlier, i will monitor some more and check out the pump, just to be thorough and also to provide as much info as possible for future readers of this post.

Eric, your thoughts are welcome as always.

. . . and also to provide as much info as possible for future readers of this post.

That should be the objective of each and every post/response.

Measuring grouphead temperature is analogous to measuring oil pressure (at idle) or engine water temperature vice simply seeing a "red light". Reading grouphead temperature under fully warmed up idle conditions on "Wednesday" and realizing that it is substantially different from that on "Tuesday" indicates that something is amiss. Having a lower than normal temperature and a slightly greater than normal delay in grouphead flow during a flush would indicate an idle leak in the brew circuit. Unfortunately, with a rotary pump, this might not be so evident.

Refilling this circuit with a short pump operation (2-3 seconds max) and then seeing the group temp climb back to "normal" would certainly tend to confirm this in the apparent absence of a flow delay.

Most group heads and the E61 group heads that i'm familiar with have a cap on the top for access to the upper brew valve. I use this to vent any air from the heat exchanger or group head which should always be done if the group head or HX is opened.

I usually initiate a brew cycle and then crack the highest access port to the group head (the top center cap on the E61) until only water and no air bubbles appear.

The problems I've had with cold group heads have always been due to air in the HX.

I use this to vent any air from the heat exchanger or group head which should always be done if the group head or HX is opened.

I'm not going to say I disagree BUT . . . I would also say that the brew circuit must be pretty darn good at venting itself, otherwise we would have a massive problem with newly built machines - not to mention the thousands of machines disassembled in this area for various purposes.

I agree with Eric.

In my opinion there would have to be some other problem with the machine in order to make bleeding off air through the top nut a viable solution. When I first started using the e-61 I had a problem with thermosyphon stall. Once I learned what it was I stopped doing short flushes and have not had the problem since.

Not lecturing, and please feel free to correct me, but to clear air in the upper pipe of the thermosyphon loop by loosening or removing the top net, the water level in the system would have to above the top of that same loop, or the system would have to be pressurized (plumbed, and/or the pump on). Otherwise, the water level would have a greater potential to equalize itself, allowing more air in.

If air is "trapped" in the upper loop, flushing the group should push the air out in a properly designed system that has been maintained.

And to add one data pint to Eric's statements, I have had my current E-61 group on my VBM apart at left five or six times in about as many months and have not had a stall. Even more times on my last VBM

Well, it's happened often enough to me that I bleed the system as a matter of routine. It's simple and often effective on exactly this type of issue.
I did not imagine this would be the least bit controversial.
What could be the harm in trying?

Not controversial at all, and making for interesting discussion.
I think the question is not is it harmful but one of is it necessary? A thermosyphon air lock in an E-61 HX machine should be easily removed by simply running the pump for ten or maybe fifteen seconds. The pump should push a great enough volume of water through to displace any trapped air. If it does not then there is some other problem like a clogged flow restrictor, dirty or scaled gicleur, dirty gicleur screen, etc., that is inhibiting flow.

As Eric said, if it was necessary then we would have seen mention of it previously as the group has been in service all over the world for 50 years. Yours was the first mention of the procedure that I have seen.

And if there is any harm it would be that the gasket could be damaged and a leak created, but I wouldn't consider that since the cap should be removed occasionally for Gicleur and filter screen inspection and cleaning, and mushroom inspection.

Next time you run into that, try just pumping water to see if that works? Just saying, not criticizing. Eric and I have had some very interesting E-61 related discussions over the last 6 months or so, and we have both learned a little (well.. he learned a little from me and I learned a LOT from him).

I cannot explain why this issue has not been discussed before. There has been a great deal of discussion about proper brew and head temps.

I'm tempted to think its so obvious people overlooked it.

Maybe the E61 is somehow different although to me it looks like this would apply especially to the E61.
I do it everytime i start up any machine from dry and don't assume the exchanger is full, I see it.

erics wrote:Reading grouphead temperature under fully warmed up idle conditions on "Wednesday" and realizing that it is substantially different from that on "Tuesday" indicates that something is amiss. Having a lower than normal temperature and a slightly greater than normal delay in grouphead flow during a flush would indicate an idle leak in the brew circuit. Unfortunately, with a rotary pump, this might not be so evident.

I agree with that statement 100% and that's why i've been fussing over this. I simply have trouble letting it go and moving on.

However, it seems my machine is starting to behave better for some reason. Again this morning it was hovering at 204-205 degrees after a 1 hour warm up from cold start. After the first shots of the morning, it slowly (thermosiphon restrictor) climbed back to its usual 209 idle. We left around 10h30am and have just come back now at 8h30 pm. Lo and behold, still idling at 209!



We will see if this holds over the rest of the weekend. I wonder if the new brew valve just needed time to seat properly.

BTW, i was able to change out the seal in the original valve so i now have a backup. I used a vice with rubber jaws and a heat gun to get the cam follower to unscrew. Yay!

I would question the condition of the brew valve's seat in the group. Did you get a chance to closely examine that? I ask because a bit of inconsistency there (scale, corrosion, etc.) could cause the delay in the valve seating.