Since I bought my car (2 months), the secondary air injection pump belt has been missing. I originally thought it was the A/C belt, and was going to replace it today, only to discover it was the air pump. My question is what does the air injection pump do? My car seems to run fine, I imagine I can purchase the belt through Mercedeshop. Thank You.

The air pump helps on emissions durning warm-up, pumps air into exhaust. Pump is probably seized. As long as California(emission test) doesn't mind then no harn as is.