my machine makes a loud screeching or grinding noise from the pump, is it broken?

Diagnosis

The loud screeching or high-pitched grinding noise coming from your De'Longhi Stilosa EC260BK is a classic symptom of pump cavitation. This occurs when the ULKA vibration pump is attempting to draw water, but instead, it is pulling air or fighting against a vacuum. Because the pump is designed to move liquid, not gas, the internal piston oscillates violently, creating a metallic screeching sound that can feel like the machine is vibrating off the counter. This typically happens for one of three reasons: the water tank isn't seated correctly, creating a gap where air enters the system; an airlock has formed in the internal tubing after the machine sat unused; or calcium scale has partially blocked the intake valve. You can confirm cavitation by checking if the pump noise is significantly louder than usual and if the water flow is either nonexistent or comes out in erratic, sputtering bursts during the brew cycle.

How to Fix It

To resolve the cavitation and prime the pump, follow these precise steps to force water through the system and purge the air pockets.

1. Power down the machine and unplug it from the wall outlet to ensure the heating element doesn't run dry.
2. Remove the water tank entirely. Inspect the circular valve at the bottom of the tank and the corresponding intake port in the machine base. Ensure there is no debris, coffee grounds, or slime blocking the seal.
3. Refill the water tank to exactly the MAX line using filtered water. This provides the maximum head pressure to help push air out of the lines.
4. Firmly press the tank back into place. You should feel a distinct "click" or seat; if it is tilted even slightly, the pump will suck air.
5. Plug the machine back in and turn it on. Do not attempt to brew coffee yet.
6. Turn the steam/hot water dial (the knob on the side) to the "ON" position. This opens the bypass valve and allows water to flow through the widest path available, which is the fastest way to clear an airlock.
7. Wait for the pump noise to transition from a high-pitched screech to a steady, lower-pitched hum. Once a steady stream of hot water flows from the steam wand, turn the dial back to the "OFF" position.
8. Now, lock the portafilter into the brew head and run a "blank shot" (water only, no coffee) to ensure the group head is also primed.

If That Didn't Work

• Perform a Forced Descale: If the screeching persists, you likely have a calcium blockage in the narrow intake capillary. Mix a solution of 100ml De'Longhi EcoDecalk with 900ml of water. Run the solution through the steam wand and the brew head in alternating bursts of 30 seconds, letting the solution sit inside the machine for 10 minutes between cycles to dissolve the scale.
• Manual Priming via the Tank: While the pump is running and screeching, gently lift the water tank up by about half an inch and then slam it back down firmly. This sudden change in pressure can often "shock" the air bubble out of the intake valve and allow the pump to grab the water column.
• Inspect the Intake O-Ring: Remove the water tank and look at the small rubber O-ring on the intake valve. If it is cracked, flattened, or missing, the pump will pull air from the room rather than water from the tank. Replace the seal or use a small amount of food-grade silicone grease to create a tighter vacuum.
• Pump Replacement: If the noise is a rhythmic "clunking" rather than a screech, the internal spring of the ULKA pump may have snapped. In this case, the pump (Part No. EPW6005) must be replaced by opening the chassis and swapping the vibration pump assembly.

Heads Up

• Avoid Dry Running: Never let the pump run for more than 30 seconds if water isn't flowing. Running the pump dry causes the internal piston to overheat, which can permanently warp the plastic housing and kill the pump.
• Water Quality: Always use filtered water. The Stilosa has very narrow internal tubing; using hard tap water will lead to scale buildup and recurring cavitation issues within 3-6 months.
• Storage Tip: If you plan to leave the machine unused for more than two weeks, leave the water tank half-full and run a quick cycle before your first use to prevent the seals from drying out and leaking air.
• Steam Dial Warning: Ensure the steam dial is completely closed before brewing. If it is left slightly open, the pump will struggle to build enough pressure for the coffee, which can mimic the sound of a failing pump.