Picking up a 2005 CLK320 from our very good friend who has kept his car very well maintained. The interior looks brand new, as if it was never used..lol Exterior needs detailed but nothing major as far as any dents or scratches or just lack of care.

I test drove his car yesterday for about an hour and as I started it up I noticed a whining noise that was weird. It would get a little louder during acceleration but then disappear at around 40+ mph. When slowing down to about 20mph to a stop the whine would come back.

I found a youtube video of a C-class that is making the EXACT same noise:

My question is how hard is it to install a alternator in the 2005 clk320?

I've done repairs on cars and have a lift in my garage, so tools are not an issue. Being this is our first German car I know things can be different from American/Japanese cars (which we own and I maintain,upgrade). When I changed out the alternator on my truck it wasn't bad at all but then again Ford's aren't crazy engineered compared to Mercedes.

Just wanted to get an opinion since the part is only about $250, but other than that the car is flawless... truly a kept piece! I just want the whine to go away.

Is there any sure way to diagnosis this and make sure it is. I asked him if he remembers the noise and he said he can remember that it was always there but perhaps not as loud? I immediately noticed the noise, where my wife was struggling to hear it (she probably needs her ears checked I guess...lol)

The noise is definitely coming from the front of the engine. He said possibly power steering pump but I don't think that is what it is at all, standing still not turning the wheel and just idling it sounds exactly as the posted above video..., and as he drives away in the video that's exactly what the car currently sounds like now...to the T.

Also note there are zero check engine lights on or alerts or anything of that nature. Nothing is illuminated on the dash that would indicated a problem.

Thanks,
-Nigel

 

Nigel, I responded with some suggestions over on benzworld. A more common source of noise are the idler and tensioner pulleys. You can remove the belt and check for rough bearings. Also, with the belt off, start the engine to see if the noise stops (indicating that it IS a belt driven pulley causing it).