Does your vacuum appear louder than normal?
Check the inner and outer circular filters and the post-motor filter for debris. Also check the upper-tank assembly, as it may need to be rinsed.
If rinsed, please allow to completely dry before putting back into the machine. Failure to properly maintain the filters could result in damage to the motor.
A clogged hose may also cause the unit to sound abnormal. Unplug your vacuum. You can check the upper and lower hoses by running a broomstick through them to push out any clogs.
Check the brush roll for hair & debris. Remove any hair/debris that is found.
Remove the brush roll and belt. Turn the unit over and test the unit after the brush and belt have been removed. If noise goes away, the brush and belt need to be replaced. To order replacements, please order online at BISSELL.com.
If still loud, please take the unit to an Authorized Service Center to have a Quality Technician inspect the unit.