Diagnosis
That's the vibration pump cavitating—it's running dry because there's not enough water in the boiler. This usually happens after descaling or if the machine hasn't been used for a while.
How to Fix It
Prime the pump. This is a three-step process:
- Fill the water tank and make sure it's seated properly.
- Turn the steam knob on the left side to the open position (clockwise).
- Turn the brew switch on and immediately pull the brew lever up. You'll hear the pump run and sputter. Let it run until a steady stream of water (not air) comes out of the steam wand. This can take 30-60 seconds.
If That Didn't Work
The issue might be a clogged solenoid valve, often from scale. Try backflushing with just water (no cleaner) to see if you can dislodge any debris. If the noise persists, the solenoid may need to be physically cleaned or replaced.
Heads Up
Never let the pump screech for more than a minute. Running it dry for extended periods can damage it. If priming doesn't stop the noise quickly, turn the machine off, let it cool, and check for other flow blockages.