Aquaclear 70 issues

[Ansomnia7]

I have inherited two aquaclear 70 aerators for my 50gallon tank and I don't believe they are functioning properly. When I first started my tank up one of the pumps created a cyclone inside the plastic aerator tube but the other one never did. I know the motor is working and causing the piston fan thing to turn. I took them out to look anthem to see if any of the obvious parts needed cleaning and they are both fine. Both motors are set to flow down.

Thanks!