my irobot roomba i3+ evo is making a loud grinding noise from the bottom, what should i check?

Diagnosis

The loud grinding noise emanating from the bottom of an iRobot Roomba i3+ EVO is typically caused by mechanical resistance in the drivetrain or the cleaning head. Most commonly, this occurs when long hair, carpet fibers, or small hard debris (like pebbles or plastic fragments) penetrate the seals of the dual multi-surface rubber brushes. When debris wraps around the ends of the brushes, it creates friction against the plastic housing, resulting in a high-pitched grinding or rattling sound as the motor struggles to spin the rollers. Another frequent culprit is the front caster wheel. Because this wheel rotates 360 degrees, it often collects hair and grit in the axle. When the axle becomes jammed, the wheel no longer pivots smoothly; instead, it "skids" or vibrates across the floor, which can sound like a grinding noise coming from the front of the chassis. In rarer cases, a grinding sound may indicate a failing gear in the side-brush motor or a foreign object lodged in the vacuum intake path, creating a vibration that resonates through the plastic body.

How to Fix It

To resolve the grinding noise, perform a deep mechanical cleaning of the undercarriage:

1. Power down the robot completely by pressing and holding the CLEAN button until the light ring goes dark. Flip the unit over onto a flat, clean surface.
2. Remove the two dual multi-surface rubber brushes. Pinch the brush frame release tabs and lift the frame. Pull the brushes out of the module.
3. Inspect the ends of the brushes. Use a pair of scissors to cut away hair and string wrapped around the ends of the rollers. Pay close attention to the square and hexagonal pegs; if debris is packed into these ends, the brush will not seat correctly, causing a wobble and grinding noise.
4. Clean the brush module. Use a can of compressed air or a vacuum to clear the intake port where the brushes meet the internal suction channel. Check for any small pebbles or coins lodged in the plastic guards.
5. Remove the front caster wheel. Gently pull the wheel assembly straight up and out of its socket. Remove any hair wrapped around the axle. If the wheel does not spin freely with a flick of your finger, use a needle to clear the axle debris.
6. Check the side brush. Unscrew the single Phillips head screw holding the green side brush in place. Remove the brush and clear the hair from the gear post.
7. Reinstall all components. Ensure the brush pegs match the shape icons (square to square, hex to hex) in the cleaning head module. Press the brush frame down firmly until it clicks into place.

If That Didn't Work

• Replace the Rubber Brushes: If the rubber fins on the brushes are torn or warped, they can slap against the interior of the module. Replace them with a genuine iRobot Dual Multi-Surface Brush set (Part # 1384444).
• Inspect the Caster Wheel Housing: If the wheel is clean but still grinding, the plastic housing may be cracked. Replace the front caster wheel assembly entirely to ensure a smooth glide.
• Check for Internal Gear Failure: If the noise persists and sounds like it is coming from the center of the robot, a gear in the drive motor may have stripped. This requires a full teardown of the chassis to replace the drive module, which is generally recommended for professional servicing.
• Clear the Suction Path: Remove the dust bin and check the black rubber flap (the intake seal). If the flap is torn or obstructed, air turbulence can cause a vibrating "grinding" sound that mimics a mechanical failure.

Heads Up

• Never use water to clean the rubber brushes or the caster wheel axle, as moisture can seep into the motor housings and cause permanent electrical shorts.
• Avoid using "generic" replacement brushes from third-party sellers; these often have slightly different diameters that cause the exact grinding noise you are trying to fix.
• Perform a "brush and wheel" maintenance check every 30 days to prevent hair buildup from putting undue stress on the drive motors.
• If you notice the robot "shuddering" while moving forward, it is a sign that the brushes are improperly seated in their pegs—re-seat them immediately to avoid stripping the plastic gears.