I did my swap last night after the voltage spikes. I could've done just the regulator, but it wasn't worth the time to do one but not both. I wanted to add my experience to the pile, I think there are some corrections to be made, but maybe because I'm more experienced in working in tight spaces and making my job as easy as possible. Some misconceptions:I recently performed an alternator swap and thought I would share my experience as well:
I noticed my iDrive flickered off and on one day, as well as my speedometer going to zero and then back to speed while driving around 35mph. 3 days and 150 miles later, while driving to work, my ABS light came on and then went off after a few seconds. 5 minutes later, it happened again. 5 minutes later...again. Then it just stayed on. Finally, a SMG yellow COG came up (transmission fault). I just so happened to be driving right by BMW of Manhattan in NYC on my way to work, and figured I would just pull it in rather than risk getting stuck somewhere.
While the car was being diagnosed, I did my own searches on M5Board and came to the conclusion my alternator and/or voltage regulator was bad
- I got a call from my service advisor several hours later, who told me I needed a new alternator. He said the alternator was overcharging the battery at 18v. They quoted me "around $2,100" including 8 hours of labor. I declined the repair and ordered a new alternator, voltage regulator, AC belt, main belt, and coolant. (At 45k, my belts were probably due for replacing anyway, and the repair involves removing them. The repair process also involves draining coolant from the radiator, at least on paper). I also flatbed the car back to my home - I didn't like the thought of frying electronics or boiling the battery on my way driving home.
In retrospect, it's possible I only needed a new voltage regulator based on my research here. It appears undercharging might be more of a bad alternator symptom, and overcharging a voltage regulator symptom - but I was more comfortable just replacing both.
Note that I recently (~4k miles and 4 months prior to this issue) replaced my car's original battery. I did not do a reprogramming of the new battery as part of this swap. It is unclear to me whether the lack of reprogramming led to this failure, or whether my then-dying battery caused a premature failure of my alternator and/or voltage regulator. (I did a DIY write-up of the battery swap and will update the OP with this information.)
My Observations from the Alternator Swap (not full instructions, just additions to the instructions and what others have posted):
- I have a 2008 M5 SMG, 10/2007 build with 45k miles
- I performed the swap on raceramps. No lift is needed.
- After getting started, I elected NOT to remove the radiator. I can confirm, as others have, that this is not necessary. I can also confirm the need to remove the black canister with the braided metal wire attached just below the alternator. Failure to remove this canister (and it's metal mounting bracket) will mean you simply can't work the alternator out of the engine bay.
- As others mentioned, not removing the radiator exposes it to damage. You'll be using a wrench to remove your belts, a pulley, the alternator, and possibly a hammer or similar to get the alternator to break loose Any one of these can damage your radiator. I used a simple piece of cardboard box to cover the exposed fins, and it worked perfectly. I zip-tied it to the plastic clip at the bottom of the radiator where the electric fan previously sat in.
- To echo another forum member - at the start of the process, you will be removing both a metal cover and a plastic cover from the top of the radiator/radiator fan. The metal cover has the hood latches attached to it...I unscrewed these.
- I used a 2-foot screwdriver to work the tabs at both sides of the fan when removing it. It's a tight fit and requires moving tubes/wires out of the way, but it does come right out the top without disconnecting anything other than what is in the instruction PDFs.
- I only had 1 connector (what I assume is the power plug) on my fan. The instructions mention a AUC sensor...I saw the bracket this would have been mounted to, but did not see my AUC sensor. The instructions mention to "modify the AUC sensor"...perhaps mine had already been modified?
- In removing the belts, after the A/C belt I had to unscrew an entire pulley to get at the alternator drive belt. Unless I missed it, the instructions didn't mention this pulley. It looks like it is offset, but can only screw in one way so don't worry about reinstalling it. All 3 pulleys had plastic caps over the nut holding them in place, that I popped off with a flathead screwdriver.
- After unfastening the tubes/lines as mentioned in the instructions (to make space for yourself), and if you elect not to remove the radiator, you have to remove the black cylindrical canister and its mounting bracket (what I've seen referred to as the accumulator). Remove the plug on the accumulator (use needle nose pliers for the metal clip and then pull the plug). Unscrew the two easy screws on the bracket (they screw in upside down, vertically). Wiggle the canister out of the bracket. It has a rubber sleeve around it which may or may not come along when you pull out the canister (either way is fine, remove the sleeve, too). The metal braided hose connecting the canister doesn't have a ton of slack, but you can indeed remove the canister without otherwise playing with the metal braided hose. With the canister out, you should be able to remove the top of the mounting bracket (lift it up and out). The bracket is still being held on by two short screws (10mm) at the very top that are hidden behind a metal line with 3 rubber pieces which protect the metal line from the alternator and accumulator bracket that it is otherwise sandwiched in between. These rubber pieces snap off (just pull on them, or push them along the metal line and then off). Once removed, you can get at the screws. As another posted mentioned, a small box wrench is all I could use to get at them. You may want to remove the lower mounting bolt on the alternator first - if you are lucky, your alternator might swing out a bit and give you a little bit of room. If you are unlucky (like me), you will need to remove the bracket first to get a wrench under the alternator to pry it off
- To REINSTALL the accumulator bracket - get the new alternator installed with just the top bolt. See if the alternator swings easily onto its bottom mounting point. If so, don't tighten it yet (as you can do this after reattaching the two top 10mm screws on the accumulator bracket). If the alternator doesn't swing easily onto its bottom mounting point, you might want to consider working the alternator first to get it properly seated and bolted (as this will be more difficult once the accumulator bracket is installed). I recommend fully assembling the accumulator bracket, not forgetting to put the 3 rubber pieces back on the metal line which hides the top 10mm bolts. Keep only the two long vertical screws loose. Take the rubber sleeve off the accumulator, and put it in the bracket. Finally, just shove the accumulator into the sleeve (and, hence, into the bracket). This sleeve trick would have saved me 30 minutes of pain. Don't forget to reattach the plug and its metal clip.