Issue with pressure being over 18+ bars on Micra
I've been dealing with persistent 18-20+ bar pressure spikes during extractions on my Micra. I bought the machine used over a year ago and never really paid attention to the pressure gauge until last week, when the machine dumped a bunch of water into the drip tray. I found that a lot of people eventually run into issues with the Expansion Valve (B.2.041), and my symptoms were similar (water dripping into the tray even while idle, etc.). There was quite a bit of scale buildup, which had rendered the valve non-operational. I cleaned it, get the new O-rings and put back together.
I also removed and cleaned the manifold (A.2.123), which had some scale inside. There was a bit of watery scale at the pipe exits fitting into it, and quite a bit of scale buildup where the manifold connects to the pressure gauge tube - all got cleaned, but I couldn't clean that super thin copper pipe, which is part of the pressure gauge assembly. Finally, I replaced the cap on the vacuum breaker valve (B.2.029) because the plastic had loosened over time and wasn't sitting snugly - some people were saying it could also be causing issues.
All of this fixed the issue of water gushing into the drip tray, but the brew pressure is still completely off. My pressure gauge is all over the place: it starts at 3 bar when the machine is warm and idle (which I think is actually normal). When I pull the brew lever, it jumps to 18 bar for a second (during my 1-second pre-infusion), drops to 15 bar, and then jerks back to 18 bar and keeps climbing way past the 18+ bar zone. After the shot finishes, it stays stuck in that 6 o'clock position for a while.
At this point, I'm not sure whether I'm still dealing with an Expansion Valve issue or if my pressure gauge is completely cooked - either from scale or from running the machine at such elevated pressure for an extended period.
One more thing: maybe I didn't lock the portafilter in tightly enough, but right after pre-infusion, it got forced down under the pressure and started leaking water - you can see it in the video. This has never happened before, which makes me think the actual pressure really is way too high.
Does anyone have any ideas what it might be?