Whirring hum tied to RPM

[SpanishHDJ100]

That is a whirring hum coming the pulleys and belts. It is tied to the engine RPM. It is present at idle and when driving. It is louder in the the cabin, particularly on the passenger side. It is present with or without the air conditioning working. The hum is present when coasting downhill in neutral too. The car is a 2000 with 75,000 (123,000kms) miles.

 

[Dirt J]

If it's coming from the pulleys and belt, then start there. You can remove the belt and inspect and turn the pulleys by hand to feel and listen. You can also spray brake cleaner in the bearings of each pulley while running to determine which one may be worn out.

 

[badlander]

Alternator brushes.

 

[SpanishHDJ100]

If it's coming from the pulleys and belt, then start there. You can remove the belt and inspect and turn the pulleys by hand to feel and listen. You can also spray brake cleaner in the bearings of each pulley while running to determine which one may be worn out.

It looks like the bottom twin belt has too much play. Can this cause the symptoms?

 

[Snow Wagon]

Based on your username, I'm guessing your 100 series has the 4.2 Liter Turbo Diesel?
If so, I'd include that info when posting about engine noises.
Most of us on the 100 series forum have the 4.7 Liter Gasoline V8.
Dirt J's reply above is "generic" and works for most engines.

As for your last question, the 4.7 V8 doesn't have a bottom twin belt
If one / several of your belts appear to have too much play, I'd check the belt tensioner(s).
Once you know where the tensioner is, watch it while the engine is idling.
If the tensioner appears to bounce / move a little up and down while the engine is idling, it's definitely bad.

Good luck with the diagnosis.
Tom