it makes a loud gurgling or grinding noise during the brew, sounds like it's struggling.

Diagnosis

The loud gurgling, vibrating, or grinding noise you are hearing is a classic symptom of "cavitation" within the internal heating element and pump system. This occurs when air pockets become trapped in the water line, preventing a continuous flow of liquid. Instead of a smooth stream, the machine is trying to push air and water simultaneously, which creates a violent shaking sensation and a loud, guttural sound as the pump struggles to maintain pressure.

This is most commonly caused by an improper seal between the water reservoir and the intake valve, or a "dry start" where the machine was activated before the reservoir was fully seated. If the intake valve is not perfectly flush, the pump draws in atmospheric air rather than water, leading to the grinding noise. You can confirm this by checking the brew speed; if the coffee is dripping significantly slower than usual or the carafe is only half-full despite the cycle finishing, you have a confirmed air lock or a calcium-based blockage in the heating tube.

How to Fix It

To clear the air lock and restore silent operation, follow these precise steps to prime the system:

1. Power down the machine and unplug it from the wall outlet to reset the internal thermal fuse.
2. Remove the water reservoir completely. Inspect the rubber O-ring/gasket at the base of the reservoir for any debris, coffee grounds, or cracks that could allow air to leak in.
3. Fill the reservoir to the 12-cup MAX line using filtered water. This provides the necessary head pressure to force air out of the lines.
4. Firmly press the reservoir back into the machine. You should feel a distinct "click" or a snug fit; if it wobbles, the seal is not airtight and the gurgling will persist.
5. Run a "Water-Only" cycle. Do not add a filter or coffee grounds. This allows the pump to push the air bubbles through the system without the resistance of coffee grounds.
6. While the machine is brewing, gently lift and reseat the reservoir once or twice to "burp" any remaining air pockets out of the intake valve.

If That Didn't Work

• Perform a Deep Descaling Cycle: If the noise persists, you likely have mineral buildup (limescale) narrowing the internal tubes. Mix a solution of 50% white distilled vinegar and 50% water. Fill the reservoir, start the brew, and let it run for 5 minutes before powering off the machine. Let it soak for 30 minutes, then finish the brew cycle and run two more cycles with plain water to remove the vinegar taste.
• Clear the Showerhead: Check the spray head (where water exits into the basket). If the small holes are clogged with oils or minerals, the back-pressure causes the pump to strain and make noise. Use a needle or a thin paperclip to clear each individual hole in the spray head.
• Check the Valve Spring: If the reservoir is seated but the noise continues, the one-way check valve at the bottom of the machine may be stuck. With the machine off, gently tap the bottom of the reservoir area with the handle of a screwdriver to dislodge any trapped sediment or a stuck spring.
• Reset the Thermal Switch: In rare cases, a partial overheat can cause the pump to run erratically. Unplug the unit for a full 60 minutes to allow the internal components to cool completely to room temperature before attempting another brew.

Heads Up

• Avoid "Dry" Brewing: Never start a brew cycle if the reservoir is below the minimum fill line, as this instantly introduces air into the pump and causes the grinding noise.
• Use Filtered Water: To prevent the calcium buildup that leads to pump strain, use filtered or bottled water instead of hard tap water.
• Weekly Rinse: Once a week, run a cycle with just water and a tablespoon of lemon juice to keep the internal heating elements clear of organic residue.
• Avoid Overfilling: Do not exceed the 12-cup mark, as this can cause the reservoir to sit too high, potentially breaking the airtight seal at the base.