Pump is running but makes a loud grinding or rumbling noise from the motor end.

Safety first: Turn off power before inspecting the pump.

• Confirm noise source: Use a mechanic's stethoscope or a long screwdriver to listen at the motor body versus the wet end. Loud rumble at the motor indicates bearing failure.
• Check for leaks: Inspect the area between the pump wet end and motor for water drips, which can indicate a failed mechanical seal that may have damaged the bearings.
• Plan replacement: Bearing replacement requires motor disassembly and press tools. In most residential cases, replacing the complete motor or pump assembly is more practical.