My car is an early C280 (straight 6). For some time now a whining/scraping noise has intermittantly been coming from the front of the engine - particularly at tickover. I think that it may be from the ac pump or its clutch. Any advice or suggestions would be very welcome.

 

You didn't memtioned the year but all Mercedes 6 cylinder engines afer 95, whether S6 or V6 tick. Why the author of the article in MBCA The STAR magazine did not say.

 

The ticking is most likely caused by aluminum heads and blocks. That's not the problem saviged is having, however. A "whining/scraping noise" is quite different from a ticking noise where I grew up.