Open it up and check the diffuser gasket. There are multiple videos on YouTube that show how to take it apart and what to expect. The Whisperflo is the same except for the motor. So, you can watch a video of the Whisperflo as well.
Basically, just remove the 6 outer bolts and pull back the motor and drive assembly.
Do not remove the 4 bolts that hold the motor to the seal plate.
Basically, just remove the 6 outer bolts and pull back the motor and drive assembly.
Do not remove the 4 bolts that hold the motor to the seal plate.