Hello,

I drive a 1985 Mercedes 300D with 178K miles on it. I keep it up fairly well and perform some of the maintenance myself or with my father. For issues that we are not equipped to tackle ourselves, we refer to a Mercedes specialist who is well versed in the language of diesel engines. Unfortunately, for me, the most recent issue was a mystery to said specialist.

During acceleration, an audible high-pitched, whirring noise occurs, consistent with the RPM. It is a tone similar to that of an RC motor or a slower spin on a front load washing machine. On longer drives it is extremely irritating and unnerving. I am concerned that it may have something to do with the electrical system.

Another (possibly related) issue that came about around the same time is the headlights flickering intermittently during warm up and from time to time during normal to extended driving.

Any ideas? I'd love to start a dialogue. Thanks!

G

 

If it is related to the lights it could be you are losing a Bearing in the Alternator.
Use a Mechanics Stethoscope or a 3 foot or so wooden Broom Handle with one end on the Alternator and one on your ear and probe around and listen.

Watch out for moving or hot parts.

You did not say if you could duplicate the nose with the Car Stationary but by raising the rpms.

 

If the noise is only happening after 2000 rpm or more it could be the Turbo Charger is worn and one of the Wheels is rubbing the housing.

 

I was wondering about the alternator... I can duplicate the noise by manually revving the engine by hand. I'll try the broom handle trick. Am I listening for a rattling sound should a bearing be loose?

btw, it's not turbocharged

 

I was thinking alternator too. I would not have thought of a broom handle as a stethescope though. That is a cool idea!