here is a DIY for you friend...

and yes,you need to add coolant, some hoses needs to come out.

here why ,top hose attached to the alternator...

http://i1140.photobucket.com/albums/...pwaterhose.jpg

600$ is a lot of money...ohhh

Thanks for the diy link. it looks like lot of work. I just put new waterpump in it two weeks ago and I wish I had know the alt. was bad too. Now all the hoses have to come off again. I have a voltmeter now hooked up to a cigarette lighter and everytime I start it I wait for voltage to climb to 14 volts and its fine. maybe i will drive like this for a while before it completelly goes out :-).

well,there is a place here in my area ,from what i know ,one of my family member ,had some problem like you have ,voltage,and he replaced it with a used one for 150$ with 6 or 12 month warranty (not sure 6-or-12)...

my alternator ,everything was fine and then one day i start hearing some big noise coming from the front, in my case a bearing was the problem,but i put new one for about 350$ with lifetime warranty at riebiest auto parts.

goodluck,friend

Alternator Removal
 

Yesterday I removed the alternator. I thought I would have to
disconnect coolant upper hose from the radiator but after I took out electrical fan there was enough space to work in there. So after removing the belt there was not much to it. Just tipped it upwards and pulled it straight forward. it is very heavy and you have to support it somehow before you get wires disconnected from, it almost broke my back.
I am getting a new one from the dealer so I will just put it in and see if voltage is constant 14+ volts. So now I know for sure 2005 4.4 x5's alternator is not watercooled and there is no need to remove radiator hoses and refill the cooling system. So all those Alternator DIYs floating out there are for older pre-2004 x5s and on those it's a real pita job. I just had to be extra carefull not to tear any radiator hoses.

Bosch usually run 13.85V for the upper limit. Pretty steady at than under all loads. (I ran a digital VM during driving for a couple of weeks just to confirm after I got the vehicle.)

I'm having the same problem with my X5 4.4 sports 2005 but other than occuring randomly, also happens at the worst possible time- on the freeway. Trans goes to limp mode, get all kinds of crazy lights in the dash (multiple faults) such as DSC, 4x4, airbag etc. I have DIS and all the time error points to communication problem DME/alternator, DME shutting down the alternator and thus low voltage to components (explains the multiple faults). All I've had to do is turn the car off and wait for 10 or so minutes and startup again and car runs fine! I removed the alternator (yep, it's NOT water cooled), checked and cleaned all connections, cleaned volage regulator and alternator, installed new battery but all to no avail.

I'm surprised you had a relatively easy time removing and putting back the alternator. I had a nasty time and had to put grease on the edges to push it in while installing it. Removing it was a nightmare. TIS and Bentley manual are all wrong saying to remove alternator straight forward. No, have to first tip it towards driver side then straight forward and out.

I'm also planning to replace the alternator. Cravier BMW dealer quotes $500 with 2 years warranty. I'm also wondering if it's just the voltage regulator ($140) that needs to be replaced.

Please let us know if your issue is resolved after alternator replacement.

Thanks!