Check the inner and outer circular filters (located under the dirt cup), the post-motor filter (behind the vented door in front of the vacuum), and the pre-motor filter (underneath the filter cup in the round center portion of the Lock ‘n Seal Lever) for debris. Reduced air-flow from dirty filters or clogs will put greater stress on the motor, increasing the possibility for overheating. check the upper-tank louvers (the slits in the plastic insert in the upper tank), as they may need to be rinsed. The filters may be hand washed in cold water with mild detergent. Only reinstall filters when they’re completely dry. Note: the white post-motor filter is not washable.
If you still experience excessive noise while vacuuming, at this point it might be best to take your vacuum to a technician. You can find your nearest BISSELL® Authorized Service Center by clicking http://www.bissell.com/support/product-support/service-centers/ or by calling 1-800-237-7691, available 24 hours a day.