e39 Watercooled Alternator Replacement (2000 540iA)

JonE39 · 07-13-2010, 11:40 PM

So I've been dogged with some electrical problems, if you want the whole story read below the dashes. It seems I need to replace my alternator, the stealer wants $1700 for this job... god they are smoking crack. I've done a VC gasket change on it so this should be easy. My book says I need to drain the cooling system but this seems a bit overzealous - I figure I can use a hose clamp on the part of the upper radiator hose that goes to the alternator and proceed normally, topping it off with OEM coolant 50/50 with distilled water once the deed is done. Thoughts?

Also, the stealer told me that the reason for the replacement is that it is overvolting the electrical system. Doesn't the voltage regulator control that or does this model have a regulator integrated into the alternator? Thanks!

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A few months back I was driving to work when the car lurched, the stereo cut out and the display flashed, "Trans. Failsafe Prog." Oh shit. After work the problem went away on its own. About three weeks later I was driving to work and it happened again, this time I noticed the battery light would come on intermittently. Also, the DSC, ABS, and Brake indicators would come one above ~1500 RPM. At this point I figured it was an electrical issue but wasn't sure. The problem went away on it own for about a month. It cropped back up a few days ago with a vengeance. Given the odd electrical things going on (stereo goofing up, mirrors failing to rotate when shifting into reverse and the others mentioned above) I was pretty confident that the issue was electrical in nature. I was also fairly sure it wasn't the tranny since a mechanical failure in there would not be so intermittent. I figured the most likely culprit was the battery, which was 4 years old and had trouble holding a charge in the past. I replaced it and sure enough, all the trouble ceased... for about 40 miles. At this point I was thinking a combination of factors were at play causing an undervolt in the system: perhaps a short, bad alternator, bad voltage regulator, even the ECU. But since I just moved to Florida and didn't have access to the tools I did in Oregon I took it to the stealer. The rest of the details may be found above.

carjoe · 07-14-2010, 09:56 AM

I can't answer about the symptoms but it looked like enough of a PITA that I didn't do it myself...mine just straight up died. Battery light came on one day and that was it. No other real symptoms.

I don't know about draining the entire system but it is pretty low in the engine bay.

Good luck.

cisco911 · 07-14-2010, 10:12 AM

The voltage regulator is part of the alternator. That could be the reason why it is over charging. Replacing that Alternator is not an easy task. Good luck on doing it yourself.

JonE39 · 07-14-2010, 01:39 PM

Well it's a situation of replace it myself or spend an extra $1500 US. The location looks like a major pain in the ass. I think, however, that if I remove the upper radiator hose and the cooling fan that I should be able to get it out... I hope.

540guy · 07-14-2010, 02:39 PM

I wouldn't know about any of the mechanical stuff, but why are you going to the dealership for that job, for 1700.

Cost me 800 at an independent shop.

JonE39 · 07-14-2010, 03:32 PM

I didn't go to the stealer for the job, I went to them to diagnose the problem.

540guy · 07-14-2010, 07:15 PM

ah sorry got it

MLue1 · 07-16-2010, 07:23 PM

I did this repair three years ago using these instructions.
http://www.bimmerboard.com/forums/posts/355405

If you don't mind working with coolant and can follow instructions this job is worth doing yourself. I took me a little over an hour to drain the coolant and take things apart. I sent the alternater out to be rebuilt, once I got it back it only took me 45 minutes to replace the alternater, refill and vent the cooling system.

EDIT: Rebuilding alternator cost $175 with one year warranty, replaced battery $69 with a DuraLast from Auto Zone in Niagra Falls, still going strong after three years.

Denis · 01-17-2011, 11:54 PM

Normally shops just can not fix these water cooled alternators.

Thanks!

MLue1 · 01-18-2011, 08:23 PM

Quote:

Originally Posted by Denis

Normally shops just can not fix these water cooled alternators.

Don't fool your self, there are quite a few that can do the rebuild. I used these guys (no afilliation):

Canadian Alternators & Starters
176 Bullock Dr. #5
Markham
L3P, 7N1
(905) 201-8984 Richard

They include the big seal but I used RTV liberally as a safe gard, remember not to over torque the alternator bolts and strip the threads.

Cheers,