Diagnosis
The loud grinding noise emanating from the bottom of your GE GDT665SSNSS is almost certainly caused by a foreign object bypassing the filtration system and becoming lodged in the circulation pump impeller. In this specific top-control model, the sump area acts as a collection point; when a hard object like a popcorn kernel, a piece of broken ceramic, or a fruit pit slips through the coarse filter, it is sucked directly into the impeller housing. As the motor spins at high RPMs to propel water through the spray arms, the object is trapped between the rotating impeller blades and the stationary pump housing. This creates a mechanical "grinding" or "rattling" sound. If the noise is rhythmic and coincides with the wash cycle but disappears during the drain cycle, the issue is isolated to the circulation pump rather than the drain pump. If left unaddressed, the object can score the plastic housing or burn out the motor windings due to increased resistance.
How to Fix It
- Disconnect the power supply by unplugging the unit or switching off the dedicated 120V circuit breaker to prevent accidental startup.
- Open the dishwasher door and remove the lower dish rack completely to gain full access to the tub floor.
- Rotate the cylindrical filter assembly counter-clockwise to unlock it and lift it straight up and out of the sump.
- Using a flashlight, inspect the sump hole. Look for the impeller—the plastic, star-shaped blade assembly located at the bottom of the pump housing.
- Reach into the sump and attempt to rotate the impeller manually with your finger. It should spin with a slight "springy" resistance (due to the permanent magnets in the motor) but should not feel jammed or gritty.
- If you feel a hard obstruction, use a pair of long-reach needle-nose pliers or a vacuum with a narrow crevice tool to extract the debris. Be careful not to force the pliers, as you could chip the impeller blades.
- Once the object is removed, rotate the impeller several times to ensure it moves freely through its full 360-degree rotation.
- Reinstall the filter assembly, locking it firmly in place, and replace the lower rack.
- Restore power and run a short "Rinse" cycle to verify the noise has ceased.
If That Didn't Work
- Check the Drain Pump Impeller: If the noise occurs specifically during the drain phase (the last few minutes of a cycle), the debris is in the drain pump rather than the circulation pump. You will need to access the pump from underneath the unit by removing the bottom kickplate and inspecting the drain pump impeller for similar obstructions.
- Inspect the Lower Spray Arm: A loose plastic cap or a piece of debris caught in the spray arm bearing can create a vibrating "grinding" sound as the arm rotates and hits the rack or the tub wall. Ensure the arm spins freely by hand without hitting any obstructions.
- Motor Bearing Failure: If the sump is clear of debris but the grinding persists, the internal bearings of the circulation pump motor have likely failed. This is characterized by a high-pitched metallic scream or a heavy vibration. In this case, the entire pump and motor assembly (typically part number GE-specific to the GDT series) must be replaced.
- Check for Tub Rub: Ensure the lower rack is seated correctly in its glides. If the rack is skewed, the rotating spray arm may be rubbing against the underside of the rack, creating a rhythmic grinding noise every time the arm completes a rotation.
Heads Up
- Always scrape plates thoroughly; the GE filtration system is efficient, but small, hard objects like olive pits can still migrate into the pump.
- Clean the cylindrical filter every 30 days to prevent debris buildup from overflowing into the pump housing.
- Avoid using "dishwasher-safe" plastics that are prone to warping; a warped plastic container can shift during a cycle and obstruct the spray arm, causing mechanical noise.
- If you hear a loud "clunk" followed by the noise, check for broken glass shards immediately, as these can permanently scar the pump impeller.