113 Engine - strange noise
 

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.

In a worse case scenario the timing chain could be too tight, which is known to cause camshafts to snap or break in half...

Just guessing I suspect the altenator or something in the belt area to have internal bearings going bad...

An over tensioned serpentine belt will eventualy destroy internal bearings to the pulleyed components...

Check it all out theory, or have a [good] mechanic check it...

Yep, it was bad bearings in the alternator. Fortunatley it was rebuildable.

Good to hear all is okay and fixed...

Thanks.