chirping/squeaking from the belt drive
 

I am trying to diagnose a higher pitched noise that is coming from the front of the engine.

This is while it idles, and it mainly bugs me because it just doesn't make the car sound as nice as it should.

Sound is intermittent, usually worse when cold. Sounds like something needs to be "Greased" (Squeaky wheel gets the grease).

I definitely have a small amount of alternator whine, which is similar in noise, but at least that is consistent and doest sound like something is worn out.

I am guessing it would be one of the tensioners, but as far as I can tell there are 2 or 3.

http://realoem.com/bmw/diagrams/d/n/197.png

I cant tell if these are two different tensioners, or the same tensioner. "4" Doesnt have a part number associated

No. Description Supplement Qty From Up To Part Number Price Notes Photo
01 RIBBED V-BELT PK6X1548 1 10/2011 11287539831 +core, ENDED

01 RIBBED V-BELT PK6X1548 1 11287631817 +core
02 Belt tensioner 1 11287549588 $101.95

03 Hex bolt M10X55-ZNNIV SI 1 07119904529 $1.33
06 Deflection pulley 1 11287549557 $46.81

07 PROTECTION CAP 1 11281435114 $2.37

http://realoem.com/bmw/diagrams/r/q/124.png
No. Description Supplement Qty From Up To Part Number Price Notes Photo
01 RIBBED V-BELT LB878-4K 1 11287536345 ENDED
01 RIBBED V-BELT LB860-4K 1 10/2011 11287512971 ENDED

01 RIBBED V-BELT PK4X860 1 11287631814 +core
02 Belt tensioner 1 11287549589 $94.46
03 Hex bolt M10X50-ZNNIV SI 1 07119905641 $1.16

I am sure replacing ALL the tensioners/belts would be my best bet, but these things arent cheap.

has anyone had any experience with a slightly squeaky belt drive, and its fix?

I dont see these things under maintenance, people just say do the belt. But I have seen many tensioners/rollers/guides/bearings whatever you call it create noise in the past.

Have you ever replace the water-pump?
At least on my 4.4i M64 engine, I replaced belts and WP and the chirping during cold (lasted about 5-10sec) is gone. Just something you may want to consider replacing cause the bearing on this WP seems rather weak.

I have not, I was hoping it would last a little longer than 75k...

Water pumps on these things should be replaced every 60K. Normally when the work is done, belts are normally replaced as well. Might be time to do that job.

Some did, but mine made this noise at around 50K-miles or so.
Now I am at 92k-miles and still on original tensioners, no chirps at start up.
I am no expert so don;t take my advise as something concrete, you may want to start with belts and tensioners first since less labor if you DIY.

sounds like the waterpump is more common from peoples replies. I just did the thermostat...

Who has the best price on a water pump?

Turner - $231

BMW of South Atlanta - $219

Ebay "Hamman" $106
BMW Engine Water Pump Quality Hamman 11517586781 | eBay

Anyone have any experience?

Those are genuine OE WP, so it's the best.
I use Graf WP for around $130 and so far it's OK, it has metal impeller like OEM.
Also go get the o-ring for coolant pipe, not sure if WP comes with it, just in case (it's only like a dollar anyway)

The best way to figure out what you need the most, is to take the belts off and spin each piece by hand. If the bearings are making noise (or have play), they need to be replaced.