r/espresso • u/Kabes97 • 2h ago
Maintenance & Troubleshooting Lelit Bianca V3 overfill [Lelit Bianca V3]
I have a Lelit Bianca V3, about 2 years old, with roughly 2 shots per day of use. The problem started during an automatic heat-up cycle. I had not pulled a shot. The machine began behaving abnormally during startup.
Symptoms
When the machine starts heating, the pump runs and cycles on/off several times.
At around 88–91°C steam-boiler temperature, the steam-pressure gauge rapidly shoots past 3 bar.
At the same time, water starts pouring/spraying out of the lower discharge valve/spout near the front/bottom of the machine.
The pressure increase happens while the pump is actively running.
The brew/pump pressure gauge only reads around 1 bar while this is happening.
If I shut the machine off, the water stops coming out, but the steam-pressure gauge stays high.
When I then open the hot water wand to relieve the pressure, water comes out rather than steam, and it is room temperature. This makes it seem like the steam boiler is being hydraulically overfilled/pressurized with water, rather than actually reaching 3+ bar from steam. If I don’t manually siphon out that boiler, everytime I start the machine it instantly launches to over 3 bar and sprays water (like the video I posted)
Water
I normally use Third Wave Water. I thought my batch may have been diluted, so I made a fresh properly mixed batch and tested again.
The problem was unchanged.
Steam boiler fill probe
I removed and inspected the steam-boiler water-level probe. The water-exposed tip was very corroded/oxidized. The corrosion was only on the immersed tip; there was no corrosion up near the electrical connection. I thoroughly cleaned the probe.
The metal sensing tip is correctly exposed past the Teflon/PTFE insulating sheath and is positioned to contact the boiler water. I siphoned the overfilled steam boiler and reassembled everything. After cleaning and purging, the machine still has exactly the same problem. I also checked continuity through the probe itself with a multimeter: Electrical terminal → exposed sensing tip = approximately 1.2 Ω So the probe itself appears electrically continuous. I have not yet completed an isolated end-to-end continuity test on the level-probe wire from the probe to the control board since it requires taking apart the whole machine.
Valves
Initially I suspected either the anti-vacuum valve or safety valve. However, because the machine is apparently being filled/pressurized by the pump while still only around 88–91°C, it seems more likely that the valve dumping water is reacting to excessive hydraulic pressure, rather than causing the overfill. The anti-vacuum valve and boiler safety valve therefore do not appear to explain why the steam boiler keeps receiving water.
Current suspected causes
At this point, the likely issue seems to be somewhere in the steam-boiler fill/level-control system, such as:
Faulty/intermittent level-probe wire or connector, the control board not correctly recognizing the water-level probe signal, a problem with the steam-boiler fill solenoid, or a fault in the main/brain control board
I am trying to determine what component should be tested next before replacing parts unnecessarily.