This is especially pronounced at idle when outside the car, but I can hear it even with the windows up while going slow in 1st gear. It is a squeal/rattle combination coming from the front of the engine near the radiator. It is not coming from the internals of the engine. I think its from the alternator, pulleys, belts, or a combination of both. Another thing to note is that my A/C is not working either. The fan blows but the compressor I dont think is working.

The noise gets louder at idle if I turn on any accessories such as lights or radio. This is why I think its from the alternator. I was planning on replacing the 2 main belts at inspection II in about a month, but this noise is killing me. What is the problem here?

I had a similar problem - like a grumbling/rattle noise from the alternator area. It turned out that the bearings in the alternator were shot. The alternator still worked, but was really noisy - I thought the engine was gonna fall apart that;s how bad it was. Anyway, the procedure I took, was replaced the pulleys and belt (very easy - go to bimmerparts.com for the parts - they're the cheapest around,and all oem from germany). While the belt is off, spin the alternator pulley by hand and if the bearings are gone, you'll hear the scraping. also, if you grab the alternator pulley, try to move it laterally - up and down, left and right. See if there is any play. If there is, then the bearings are shot, and you need to replace/rebuild the alternator. Anyway, I did all that, replaced the alternator and it is nice and quiet now.....

Don't wait for the Insp II. Just do it now..

Do you replace the tensioner also?
Do you have to take the radiator out to do this or can you pretty much do this from the top of the engine bay?
Any precaution before removing the belts?

Thanks.
I'm due for this also. the intermittent but embarassing squeal is killing me.

-E-

Yeah, a squeal on a BMW is a no no :D
You don't have to replace the tesnioner, but depending on the age and the mileage, i'd check them - I didn't change mine. Just see if they have spring and tension. The tensioner should move fluidly/smoothly (with effort) when you go to retract it. No need to remove the radiator either. I know it looks awfully cramped in there, but you can get at everything with the radiator in place, and the belt will slide right over the fan blades. if you wish, you can remove the fan and shroud, but I think it is a waste of time. No precautions I can really think of. The only thing is to slowly retract the tensioners using either an allen wrench with a handle or an allen wrench socket (much easier). To remove the alternator, you need to remove the air box to gain access. Otherwise, it is a pretty straightforward job. I think about 2 hours (if you take your time) to remove and replace the pulleys, alternator and belt.

As a final note, and I mentioned this before, bimmerparts.com has great prices on these prices. But, the alternator i got was a reman from Autozone for $170 with a lifetime warranty. I know it is tabu to put one in a bimmer, but it is a Bosch chassis with lifetime warranty on the internal components, so I think it is a great deal. That was for the 80amp, BTW.

Good luck!
jb