Loud alternator

[BennyM]

Hey guys. So, I was hoping to coast through the winter without having to do any repairs to the 5er. Right. Lately, though, my alternator has been getting noisier and noisier. Seems to be the worst whenever the temp drops or if the car has been sitting for a few days. It sounds like metal on metal scraping, and can be heard from inside the car while driving. It's definitely not a screechy belt. At first I thought the engine had run out of oil. So far, the engine fine and the voltage to the battery is stable (though, I'll be keeping my eye on that with the OBC). I'm just wondering if I should replace this immediately or if I can wait until spring. Or can I just clean it?

Will try some WD40 on the front bearing, but I don't think it's going to do much.

[shogun]

might be the regulator or the slipring, or simply the belt tensioner roller bearing.

[Ross]

Remove the belt and isolate your noise by spinning everything by hand. Any bearing making as much noise as you describe could be ready to seize. That will likely toss a belt and cause other items(water pump?) not to turn. Best to heed the warning it's giving you and fix it. WD40 won't do a damn thing.

[BennyM]

The noise went away and has been gone (or at least significantly quieter) for a week now--our first week above freezing for the year. I had some other people listen to it and they concluded that it's a bearing, but probably isn't on the verge of seizing. If it becomes more consistent, I'll have to deal with it. Otherwise, I'm going to just wait until spring. Perhaps when the temp dips below 0 F again, I'll be able to pin point it better. Thanks for the input, guys.