In my 1992 300TE 4 matic, the Engine Fan is scraping the driveshaft (?) driven pulley (low, center pulley).

The scraping is getting worse. It only scrapes on that one pulley.

Without taking off the radiator yet, I checked the fan. The fan does not appear to be loose. The pulley is not obviously loose.
This just started in the severe cold weather and got worse in 1 day.

Might I have a deteriorating fan clutch? Anything I should prepare to check before pulling the radiator to I can get at the area?

Thanks!