[jfirwin]

This DIY really helped.

My M3 was built in Feb 02, so I made sure I had the right idler pulley. (Thanks, Theodore!)

While I was at it, I also replaced:

the accessory belt
the accessory belt tensioner
the accessory belt pulley
the A/C Belt
the A/C belt pulley
and the A/C belt Tensioner

ECS tuning part #2777259

BTW, you can get away with not replacing these, (except the belts) when you start hearing that squealing from under the hood (mine started around 85K miles) it'll be the idler pulley. I've always believed that you should replace parts that'll liable to go bad while you are at it. The pulleys all run on bearings, so they will wear out at some point.

I couldn't get the accessory (alternator) belt off without removing the idler pulley. Perhaps someone knows a better way?

The tensioners and pulleys are 14mm bolts, less the idler pulley.

Those bolts are not on super tight, so make sure you don't wrench them down too tight.

Remember there are rubber bushings that can be crushed.

Be super careful of the radiator overflow hose. The nipple on the upper radiator breaks easily.

The hardest part to removing the fan housing is getting it past the upper radiator hose. Be patient, be careful, and you can get the housing out without breaking anything. (I didn't)

+1 for removing the underbelly cover. Not only does it make it easier to reattach those lower hoses, but also to retrieve those dropped parts/tools.



edit - Just noticed that the picture below is wrong. The A/C / Power Steering Belt goes OVER the Power Steering pulley (#3), not under. It also goes UNDER the Idler pulley (#5), not over. See the pic below.

edit edit - So, ECS sent me the wrong belts. The correct belts for my pre-May 2008 are 6PK1067 and 6PK1460