Originally Posted by gsxr

Brakes are safety items - don't cheap out on them. OEM rotors are NOT expensive. Buy new rotors, end of story. They're a whopping $28 each for Balo rotors at ***************, or $34/ea here at MBShop (link at top of page). They're a PITA to replace on the front of a W123, though. Use the OE/dealer neon-green wheel bearing grease if possible (it's not expensive), and do NOT mix grease types. Don't forget to order new grease seals, and use a dial indicator to set the wheel bearing end play (the spec is stupidly tight, 0.01-0.02mm, or something like that.)

Another option is to upgrade to 560SEL brakes, which are vented... the 123 has solid front rotors, which are a little undersized for the weight of the car.