DIAGNOSIS That grinding noise is almost always a tiny piece of debris—like a bit of coffee ground or mineral scale—jammed in the internal pump. It’s trying to push water through a blockage.
FIX You need to clear the water path. 1) Unplug the machine and let it cool. 2) Remove the water reservoir and the drip tray. 3) Take a paperclip or a thin, stiff wire and gently probe the exit needle in the K-cup holder (the one that punctures the bottom of the pod). Wiggle it gently to dislodge anything stuck. 4) Run several water-only brew cycles (without a pod) to flush it out.
IF THAT DIDN'T WORK If the noise persists, the pump itself might be failing due to severe scale buildup. You’ll need to descale the machine with Keurig’s official descaling solution or white vinegar, following the specific descale mode instructions for the Supreme Plus to clean the internal lines.
HEADS UP Don’t ignore this. Running it with a blocked pump can burn out the motor, and that’s a much more expensive fix.