How to tell alternator bearing is going?

[supark]

I hear a metallic screeching sound on startup. It only lasts about a second or so after I start the car and subsides completely as far as I can tell when the car is running (though it may be that the bearing noise is being covered up by the sound of the engine).

I had a similar noise in my old 540i (a 97, I currently have a 99), and it didn't go away after I replaced all the idler pulleys (though they definitely were shot at about 100k miles).

Before I just start throwing out good parts potentially, what is the best way to check if the bearing is going out on the alternator?

[SHWELL]

Put a screwdriver to it, and you will be able to feel it. Don't put the screwdriver in it, just on it, the vibration will travel up the screwdriver... There may be other ways to do this.. It is still early and I have not had my Red Bull yet...

[DHoang]

Put a screwdriver to it, and you will be able to feel it. .

YOu can also place your ear over the handle end to see whether you can "hear" noise any clearer. A mechanic's stethoscope is great for detecting these sort of noise problems.
:buttrock

[Jim530i]

Put a screwdriver to it, and you will be able to feel it. Don't put the screwdriver in it, just on it, the vibration will travel up the screwdriver... There may be other ways to do this.. It is still early and I have not had my Red Bull yet...

I was not reading your reply correctly and thought, put a screw driver into it? Had that picture going in my head and it was pretty funny...

But if the bearing is going bad wouldn't the charge light on the dash come on...

[JolietRomeo]

I am having the same issue with the high pitch noise. I added some coolant to the reservoir and it appears to have subsided slightly. I am not having any issues with battery charging, acceleration or operating temps. I just don’t want the alternator shearing off as I’m going down the highway. If you are able to find out if that is exactly what is going on please let me know.

[Shardul]

Put a brass rod to the part and hold it to your ear and you will be able to tell where the noise is coming from. Be very careful while doing this.This is what I did when my alternator idler pulley was making a grinding noise.

[SHWELL]

I have no exp with this, but the Water pump may be the prob for the one with the Res fill fix..