I've experienced some odd behavior from my Expobar Office Lever that I'm hoping some more knowledgeable folks might be able to explain to me (I'm a former auto mechanic and enjoy learning how things work and why). I'd been meaning to descale my machine for a few months, but a recent move delayed that. I just performed a complete descale of the boiler and the HX system, and noted the following weird things.

Weird thing #1: after the move, using the same grinder and the same espresso, I had to grind noticeably finer in order to achieve the same ~2.5-3.0 oz in 25-30 sec. Randomly this past week, without adjusting anything, my shots began pulling very short (~1.0-1.5 oz in 30 sec). I adjusted my grind coarser, and wound up with a setting that was what I had been using previously prior to the move. FYI, I'm using a nearly new Compak K3 Touch grinder. So what's up with the random shot volumes? Did my pump decide to momentarily get stronger?

Weird thing #2: prior to the descale, I'd noticed a slight reduction in initial cooling flush water temp, combined with noticeably increased recovery time and continually dropping temperatures throughout the shot (the shot would start with temps around 204-205F, then end at 196F 30 sec later). I attributed this to scale build up. So I descaled everything, and even removed the mushroom and found the gliceur chamber to be relatively scale-free. After the descale, I experienced even lower initial temps, even longer recovery times, and even more temperature degradation throughout the shot. This result seems to be the exact opposite of what should have happened by descaling my machine. So what's up with that?

Weird thing #3: this morning, 4 days post descale, I went to do my cooling flush and the brew temp started at 160F and dropped from there -- the machine had been on and warmed up for about an hour at this point. I figured something was better than nothing, so I brewed a shot and the temp remained between 160F and 150F. The heating element cycled on/off as necessary, and the boiler pressure remained at it's normal 1.3 bars* (more on this later - it's basically an erroneous gauge reading). I decided to see if I could steam some milk, so I opened the steam wand and a little bit of water came out, then I heard a very faint popping sound, noticed that the boiler pressure gauge immediately dropped down to ~0.5 bars, the heating element kicked on and stayed on until the pressure went back up to 1.3 bars as if the machine hadn't really been up to pressure beforehand. I waited about 2 minutes and pulled another shot -- this time, the temp started @ 175F, which means the brew temp went up by about 15 degrees in 2 minutes. What in the world could cause something like this?

Side note:
I've suspected since I purchased the machine used about two years ago that the boiler pressure gauge was inaccurate. With the machine off and opening the steam valve to ensure no pressure was in the boiler, the gauge would read 0.4 bars at rest. With the machine operating, the heating element would shut off at 1.3 bars, and back on at 1.2 bars, which lead me to believe the gauge was in error by 0.4 bars (i.e. the 1.3 bar reading minus the 0.4 at-rest reading = 0.9 bars, which is what I've read most Expobar owners run their machines at).

With my machine acting up like it did this morning, I decided to do some investigation. I removed the boiler pressure gauge + line and cleaned them both. I ended up taking the gauge apart, and could see where someone else had taken a flathead screwdriver to the gauge indicator plate (the part with the graduated markings on it). Long story short, I reset the indicator plate to read zero with the indicator at its no-pressure resting point. I re-assembled everything, and now with the machine off it reads 0. With it on, the heating element turns off at 0.9 bars, and turns back on at 0.8 bars.

I let the machine warm up and pulled a shot. I still noted a lower than normal cooling flush temp (begins @ 206-207, whereas prior to the move it was at 210-212), and still noted excessive temperature degradation throughout the shot.

I adjusted the pressurestat up for a boiler pressure of 1.05. I've only pulled one shot at this new setting, but was pleased with the results. While I delayed beginning the shot too long after the cooling flush (initial shot temp was 205F), the temp was very stable, maintaining 200F throughout the entirety of the shot. I think this new setting will work once I get a proper cooling flush protocol in place.

Nevertheless, I'm still vexed about why my machine has demonstrated such erratic behavior. Any insight would be much appreciated.

Weird thing #3: this morning, 4 days post descale, I went to do my cooling flush and the brew temp started at 160F and dropped from there -- the machine had been on and warmed up for about an hour at this point. I figured something was better than nothing, so I brewed a shot and the temp remained between 160F and 150F. The heating element cycled on/off as necessary, and the boiler pressure remained at it's normal 1.3 bars* (more on this later - it's basically an erroneous gauge reading). I decided to see if I could steam some milk, so I opened the steam wand and a little bit of water came out, then I heard a very faint popping sound, noticed that the boiler pressure gauge immediately dropped down to ~0.5 bars, the heating element kicked on and stayed on until the pressure went back up to 1.3 bars as if the machine hadn't really been up to pressure beforehand. I waited about 2 minutes and pulled another shot -- this time, the temp started @ 175F, which means the brew temp went up by about 15 degrees in 2 minutes. What in the world could cause something like this?

Vacuum breaker stuck closed by scale.

Alan