Well after 6 months, my airstream fans (120mm) are hitting my airplex 360 Radiator with their blades. My fans are upside down. Air blows from under to above. So i think the motor of the fans is s getting wearing off. Its only for now 1 fan, but hearing a noise from blades that hit metal isnt realy funny, so i disabled this fan.

AC know with this problem? Is there a easy fix or do i need to buy a new airstream/papst fan?

Quoted from "Stephan"

Try to adjust the screws of the fan. Normaly this will solve such problems.

Nope already tried that. It still hitting the radiator.