It is not uncommon for the sun visor hinges to break.Google+
Car Problem Reports
Mercedes-Benz SLK230 Hinges For Sun Visor May Break
Mercedes-Benz SLK230 Problem
Average Mileage: 130,666 mi (77,000 mi - 195,000 mi)
Visitor, 2002 Mercedes-Benz SLK230
sun visor hinges broke. I removed it but cant find a replacement source or a part number. Will I have to go to the dealer for my SLK 230?
Visitor, 2003 Mercedes-Benz SLK230, 120,000 mi
driver's side visor hinge broken and visor hangs
The driver's side sun visor hinge keeps breaking. This is the second time I am replacing it, and I am told by Mercedes that they no longer make the part. Wonderful! What am I supposed to do now? Drive without one???
Visitor, 2000 Mercedes-Benz SLK230, 77,000 mi
I have now had two driver side sun visor hinges break within 2 years.
Visitor, 1999 Mercedes-Benz SLK230, 195,000 mi
Sun visor broken, does not stay up, just hangs. Have not fixed, still looking for parts.