New random issue. Mechanical fan is hitting the harmonic balancer pulley, or whatever that big pulley at the bottom is.

Swapped the fan clutch for a napa one about 3 weeks ago and it was fine till today. I checked the nuts to make sure they hadn't come loose and they are tight. Belt looks aligned so I don't think anything became misaligned. Any ideas?

Thanks!

 

Balancer coming apart ?

 

Check the rubber ring between the inner and outer hubs of the balancer. If it is cracked or pushed out on either side, or even in just one spot, replace it. Both inner and outer hubs should be flush. Check the fan blades themselves as well for any signs of wobble or cracks, etc, just because.