I just acquired a 99 SL with a 113 engine (80k miles). It runs great, but there is a disturbingly loud noise coming from the right front of the motor. I'm not sure if it's from a belt driven accessory (such as the alternator) or something in the cylinder head. The sound is a loud metallic whirring, seems to occur from idle - 2000 rpm (not sure if it stops at that speed, or the other engine sounds just drown it out). The closest thing I can equate it to is the sound of a large heavy-duty drill at full speed. No warning lights are it.

Because the sound seems to be faster than the engine speed, I'm afraid it may be something camshaft-related. Having never owed an OHC motor before, do cam bearings go bad?

Thanks for your advice.