my roomba i3+ evo is making a loud grinding noise when it runs, sounds like it's coming from the brushes.

Diagnosis

The loud grinding noise in the iRobot Roomba i3+ EVO is almost always caused by "hair winding," where long fibers, threads, or pet hair wrap tightly around the drive axles of the dual Multi-Surface Brushes. As the hair accumulates, it creates friction and tension against the brush housing and the motor's drive gears. When the brush attempts to rotate, the compressed debris acts like a brake, causing the motor to strain and the plastic components to vibrate or "chatter," which manifests as a loud, mechanical grinding sound. In some cases, the grinding is exacerbated by a "seized" brush cap. The end caps on the i3+ EVO are designed to be removable, but when hair gets trapped beneath the cap, it pushes the brush slightly off-center. This causes the brush to rub against the plastic chassis of the vacuum. You can confirm this by turning the robot over and attempting to spin the brushes manually with your finger; if there is significant resistance or if you see a "nest" of hair concentrated at the ends of the rollers, the axle is the root cause.

How to Fix It

Follow these precise steps to clear the drive system and restore silent operation:

1. Power down the unit by pressing and holding the CLEAN button until the lights go out to prevent accidental activation during cleaning.
2. Flip the Roomba i3+ EVO upside down on a flat, clean surface.
3. Locate the two pinch-tabs on the sides of the green brush frame. Squeeze these tabs firmly and lift the entire brush cage assembly out of the robot chassis.
4. Grasp the two green Multi-Surface Brushes and pull them straight out of the cage.
5. On each brush, locate the removable end caps. These are the plastic pieces at the ends of the rollers. Pull these caps off. You will likely find a dense ring of hair and lint compressed against the axle; use a pair of tweezers or a seam ripper to remove every strand.
6. Examine the opposite end of each brush where the square and hexagonal drive pegs are located. Use a small pair of scissors to carefully cut through any hair wrapped around these pegs. Be careful not to cut the rubber bristles of the brush itself.
7. Inspect the brush cage (the plastic housing) for any trapped pebbles or hard debris that may have been rattling against the rollers.
8. Slide the brushes back into the cage, ensuring the end caps are snapped firmly back into place.
9. Lower the brush cage back into the robot and press down until you hear a distinct click, signaling the frame is locked.

If That Didn't Work

• Inspect the Side-Brush Gear: If the grinding persists, the issue may be the side-brush (the small spinning brush at the front). Pull the side-brush off by tugging it straight up. Check the gear shaft for hair. If the gear is stripped or the brush is worn down to the plastic, replace the side-brush module (Part # 171463).
• Check the Main Drive Wheels: Occasionally, a grinding sound is actually a pebble trapped in the tread of one of the two large main drive wheels. Gently press the wheel to see if it bounces; if it feels "stiff," remove the wheel by unscrewing the three Phillips head screws on the bottom of the wheel module and clear the debris.
• Clean the Rear Caster Wheel: A clogged caster wheel (the small swivel wheel at the front) can cause the robot to "hop" or vibrate, which sounds like a grind. Pull the caster wheel module out of its socket and remove the accumulated hair from the axle.
• Verify the Vacuum Motor: If the noise occurs only when the vacuum is suctioning (and not when the brushes are spinning), a hard object like a coin or small toy may be trapped in the impeller. Remove the dust bin and check the suction path for obstructions.

Heads Up

• Bi-Weekly Maintenance: If you have long-haired pets or carpets, you must clear the brush axles every 14 days to prevent the motor from overheating.
• Avoid "Over-Winding": Never use a vacuum cleaner to suck debris out of the brush axles; this can pull the brush out of alignment. Always use manual tools like tweezers.
• Replace Worn Brushes: Once the rubber bristles on the Multi-Surface Brushes begin to fray or tear, they can wrap around the axle more easily. Replace the brush set every 3-6 months.
• Avoid Wet Debris: Never run the i3+ EVO over wet spills. Moisture causes hair and dust to clump into a "paste" that hardens on the axles, making them significantly harder to remove and increasing the risk of motor failure.