Thanks. I think I may have to tighten up that finicky AC #2 bolt underneath the vehicle just a bit more, I get a little occasional squeal on start up from that AC belt. SMH

A few things I've learned about the A/C belt and pulley; hope this helps.

Having the right tools (below, not expensive) turns this from a knuckle-busting frustration into a 30-minute job.

* If you're getting a squeal from your belts when you start the engine, don't just assume it's the easier-to-change serpentine belt and tensioner. Don't ask how I know :-)
* An easy test for which belt is squealing: while it's squealing, turn off the A/C with the snowflake climate control button. If the squealing stops, it's your A/C belt.
* Both torx bolts are T45, but a T40 is a lot easier to fit on #2 - especially if you use a 1/4" T40 socket.
* I loosened #1 a half turn with a 1/2" drive T45 socket from above
* I loosened #2 from below enough to slip the belt off the tensioner. Had to loosen it a lot further to get the new belt to fit. Used that 1/4" T40 bit and a 9" 1/4" wobble extension from Harbor Freight. Turn counter clockwise to loosen, just like a ordinary bolt. I threaded the bit and extension through a hole in the large shiny black subframe, just forward of the engine.
* Taking off the A/C belt requires pulling the serpentine belt from the crankshaft pulley; you don't have to take it all the way off all the pulleys. However, if you're going to replace the A/C belt, you might as well replace the serpentine belt, too. The tensioner is a T60 Torx

I’m not sure anyone referenced this yet in this post. Both bolts should be torqued to 22nm. They lock then tighten to 22nm. You don’t have to remove the upside down bolt to Dremel a flathead slit. With the fan removed you have enough room.


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+1 on slotting the AC tensioner bolt!

On my 2007 4.8i with adaptive drive the adjuster head is nearly impossible to access.

The tensioner pulley+bracket is very overpriced from bmw. If anyone needs one let me know, I am selling OEM INA replacement pulleys without thr bracket for half the price.

-Rich

www.newtis.info. throw the last seven of your VIN in and hit submit. "AC belt" in the first search field and the first result will be the procedure you desire. Cool eh?