I'm running a Vetrano on a timer and normally at walk up in the morning the grouphead static reading on erics grouphead thermo is 207-209 and the first flush is lots of steam and top temps of 210-212. about a week ago the walk-up reading would be in the 170s and a flush wouldn't get me above 190. I figured i have a vapor lock caused by a calcified vacuum breaker. it did correct itself after blowing off some steam. i ordered a new vacuum breaker and replaced the old one a couple of days ago. The old piece wasn't as gunked up with calcium as much as just having a dried out looking gasket where it seats in the silicone washer (i think). anyway it worked fine... for a day.

This morning the grouphead reading was back at 174 and after releasing some steam and running some water through the group i got it up to 204, but no higher and no steam / gurgling at the group.

My Pstat cycles on at .95 and off at 1.15. it is currently taking 8 seconds to heat up and 1:40 to cool down once it's warmed up to 204 at the grouphead.

i don't notice the fill coming on (so i'm assuming no leaks) and i don't hear any steam release inside the machine at idle

I must've done something to the machine when i replaced the insides of the vacuum breaker valve. I initially tried to remove the bottom piece of the valve, but it seems to be set in there with loctite or something and i couldn't get it to budge then i realized i could just replace the guts. This is really straight forward repair so it's hard to imagine what i could have moved or damaged.

Any ideas? Thanks all in advance... -Will

Interesting... i'll give it a try tonight. it's odd i could get it up to about 204 by bleeding steam and waiting, but then an hour a half later it would be back to 175. I'll let you know how it goes. Thanks Eric! -Will

It sounds like a possible thermosyphon stall. See the illustrated article I wrote on the subject:
Understanding and Preventing Thermosyphon Stall

Doesn't seem to be the water sensor. I ran a number of measurements, forcing refills in between and always came up at about 4.75" off the bottom of the boiler.

Thermosyphon stall would explain why i can get it almost up to temp for a while after a number of flushes but then a few hours later it's back down to 175 degrees. the longer it sits the more air is slowly entering the system. You don't think i'd hear a leak? i do remember seeing the tiniest bit of water occasionally at the top mushroom cap nut at that teflon washer. there is some scale there as evidence. I suppose i should replace that teflon washer and see what happens. Any other ideas?

This makes sense... the thermosyphon is compromised which is keeping me from getting the temps above 204 and the huge drop after a long idle. I can eventually get it up to 204 but not higher because I'm getting HX water that is cooling too much on the way to exit because the whole circuit isn't getting hot enough without the proper thermosyphon.

Wow... i just read your post on checking / descaling the mushroom... it's like "The Complete Idiot's Guide to Descaling your E61 Grouphead" GREAT reference. THANK YOU. I have to track down the big wrench and i'll give it a shot. I have some Dezcal for when i get the nerve to try a full descale... did you ever work out how to descale a Vetrano?

Well... descaled the mushroom and thanks to Eric's detailed instructions all went as planned and was very simple. Had some scale that looked like barnacles on the mushroom and after, now have clean brass. I'm having extension problems posting pics, so will do that another day. I was very optimistic, all back together, no more tiny droplets at the nut, lever super smooth... went to dinner and came back to... 174 degree group back to square one, at least i have a clean group and a new vacuum breaker! what's next, or am i shipping this thing to Chris?!?