I just descaled my VBM DDv2 after about 2 years of daily use. The mushroom showed some scale but it wasn't too bad. I used dezcal and let it sit for a few hours. Everything looked pretty clean and the mushroom appeared fine (the surface was clear, the little holes were clear, the screen was clear, etc.).

However, the temperature shown on my erics adapter is about 10-15 degrees (F) lower than it was. The espresso also tastes sour. The PID shows the temperatures to be the same as before. I've also changed the setpoint up and down; the PID changes but the group head temperature doesn't change as much upward as the boiler temp.

Does anybody have any suggestions on what to look for as I take things apart, again?

Sounds like you might have something blocking the thermosyphon? Could be flaked scale or something like that.

Thanks for the tip. I think you might be right.

I didn't take apart any boiler parts but it looks like I'll need to do that. There is a flow restrictor in the top thermosyphon tube that seems like it's not flowing water at all.

After brewing some shots and experimenting with temperature settings I'm thinking that the change in temperature might be due to opening up the lower thermosyphon tube rather than a restriction in the upper tube. I'm thinking this because the temperature of the water exiting the group head seems to be more heavily based on the temperature at the bottom of the boiler. Since there is a flow restrictor in the upper tube the flow if the descaling opened up a restriction that had previously caused by scale might cause the behavior I'm seeing.

At some point I'll take the beast apart and investigate further. For now, increasing the PID setpoint is giving me decent brew temperatures. I'm glad I've got the group head thermometer!

Did you find a solution?