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DIY: Do It Yourself
Post here to share or improve your wrench turning skills! All BMW E46 DIY tips, tales, and projects discussed inside. Learn to work on your car and know the right BMW parts you will need!

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Old 08-19-2012, 03:54 PM   #1
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Lightbulb *** E46 M3 Alternator DIY ***

So since i was on a little budget this month due to school.

Tools needed:

* Allen Key
* Torx 50
* Small Philips Screw Driver
* Flat Head Screw Driver
* Ratchet
* Socket # 10, 16, 17.
* Extension
* Towel

1. Disconnect the positive terminal from your battery

2. Start taking off your OEM/Aftermarket Intake scoop & filter and cover so you have enough room to take off the Alternator.

There is 4 clips thats holding the scoop

4. Intake scoop is off.

5. Take off the side plastic pieces that's attached to the fan cover. There is two clips on each side that gets this loose. This will help you get more room at the end when you are going to pull the alternator off.

6. Take the cap off so you can get access to the long bolt that is holding the alternator down. I simply used a little Philips screw driver to pop it off and bingo you will see the bolt. Its a 16mm bolt if you have a breaker bar your life will be much easier compared to a regular ratchet.

Cap off

7. Below the alternator drive, there is a tensioner to get the belt loose. It has a black cap/cover just like the alternator.

8. Once you took the cap off the tensioner uses a Torx key size 50 i attached it to my ratchet and pressed down on it just the way i tighten a regular bolt. This will get the belt loose gently slide the belt out from the alternator drive.

9. Now you can take the long bolt out that holds down the top portion of the alternator.

10. Take the bottom bolt that is holding the alternator as well.

11. Use an Allen key to remove the hard oil lines make sure you put a towel underneath the oil lines so you don't get oil on the alt. It will be just a little oil but i still ended up covering the alternator.

12. Oil lines removed

13. Disconnect the negative wire from the alternator. Its held by a metal clip i simply took it off with a flat head and it just came off.

14. Disconnect the positive cable from the alternator. Its a 17mm socket see the pictures below.

15. After you disconnected the cables. You can start taking off the alternator by moving it back and fort depending on how old your alternator is mine was pretty easy to take out.

If i missed something feel free to fix my mistake.


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Old 08-19-2012, 04:15 PM   #2
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Ha! This is a sweet DIY. I will bookmark this. Thanks!
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Old 08-20-2012, 02:25 AM   #3
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You just saved my $300 in labor at the shop. Thank you so much.
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Old 08-20-2012, 07:40 AM   #4
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What was the size of the allen key?
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Old 08-20-2012, 08:51 AM   #5
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Kudos on the DIY
You don't have to remove that oil line if you have small hand/fingers
When reinstall, make sure the little notch on the pulley bolt fit into that small slot there up top.

but ya, it's straight forward process.
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Old 08-20-2012, 11:48 AM   #6
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Haven't had to touch the alternator on my m3 but I took it out multiple times from my 330.

be patient getting it out, it takes a little wiggling. I would personally take the whole fan shroud off to make room to work. Would imagine it would be tricky getting the alternator out otherwise .
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Old 08-20-2012, 12:11 PM   #7
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wow first post and its a awesome DIY. And here I thought this forum was dying. Thanks for keeping the E46 community alive!
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Old 08-23-2012, 09:32 PM   #8
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good instructions, I have replaced mine before, I did not remove the oil lines. Seriously thought, screw bmw for putting such a shitty alternator in the car
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Old 08-25-2012, 07:02 PM   #9
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Good DIY mate.
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Old 08-26-2012, 01:02 AM   #10
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great DIY. Might be doing mine in a while... BTW did your alternator go bad or was it preventive? Also miles on the unit?
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Old 08-26-2012, 12:44 PM   #11
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Originally Posted by skeeterv View Post
great DIY. Might be doing mine in a while... BTW did your alternator go bad or was it preventive? Also miles on the unit?

Yes mine went out at 57k miles. I had the battery light lit up on the cluster.
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Old 08-28-2012, 12:22 PM   #12
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Excellent thread!

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..cause it ain't hard to tell. "
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Old 08-30-2012, 12:14 AM   #13
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Well done, the only discrepancy I have is that you don't have to remove the oil lines. The only issue they cause is getting to the back of the alternator for the connections and the really aren't too hard to get around. I don't have small hands and managed just fine to get in there to disconnect the negative connection by hand. The positive has enough slack to get the alternator out before undoing it.
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Old 11-01-2012, 10:15 PM   #14
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nice write up, thanks!

i'd just like to mention that when removing the negative clip, you push down on it and that releases the plug. there's no need to remove the clip itself. it's similar to the plug you remove when changing the oil filter on the m3

Last edited by JetBlackE46; 11-08-2012 at 04:00 PM.
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Old 11-04-2012, 05:03 AM   #15
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Done this on my car 156kmiles done as I was getting a flashing battery light on the dash, read up some stuff and forum members were pointing at the Voltage regulator on the alternator. In the end I bought a new alternator at a cost of 154 with a 30 refund when I return my old unit.

Anyway I used the op to help me out taking the alternator out except for I didn't have to remove everything mentioned only the fan housing for better access and the air scoop and air filter, I then got easy access to the Alt. Took me no time at all about 30 mins in total. I also took the benefit of fitting new belts as the serpentine belt was cracked all the way round, so good job really.

Just to confirm on my model 2000 328CI I had the Torx 50 bolts in the tensioners as some have mentioned an Allen head bolt in there..also the serpentine belt tensioner was stiffer than the AC one so watch the Torx Head socket doesn't come out as you could easily damage the radiator matrix, so take your time on that one..The AC tensioner was easy..

Thanks for OP for starting this thread..the E46 forum comes to assistance again..thanks.
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Last edited by rossi0112; 11-04-2012 at 05:08 AM. Reason: mileage put in
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Old 04-07-2013, 08:42 PM   #16
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I have an 01 325i.

I noticed this tube on the under-aft side of my alternator, it looks loose. Is this tube supposed to fit onto the alternator snug with a metal clamp or is this it? Any advice helps! Thanks


Last edited by Bimmerboye46; 04-07-2013 at 08:46 PM.
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Old 06-04-2014, 02:02 AM   #17
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Just wanted to say thanks. Tensioner on my 06 M3 cab was an 8mm hex, oil lines were removed with a 6mm hex (be careful with the o-rings!). This is another good reference thread.

Valeo out at 47k, Bosch reman from AutohausAZ in. Cross your fingers I don't have to do this again any time soon. Royal pita.

PS don't do this when it is 108F.

Last edited by TopazCoop; 06-04-2014 at 02:12 AM.
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Old 10-06-2014, 12:07 AM   #18
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OP, if you just get the nut on cable loose (useing a ranch wrench) , and than take out the alternator bolts (ones that mount on the motor), and than remove the cable completely, will this help to avoid takeing off the oil line ? im planning this for my car soon, id rather not disconnect the oil line if i dont have to. thanks in advance.
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Old 03-05-2015, 01:55 PM   #19
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Which to buy?

So what brand is everyone using for an alternator these days?
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Old 05-07-2015, 09:47 AM   #20
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FYI: My car (2003 M3) was NOT a T50, it was a hex 8mm.
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