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DIY: E46 M3 Alternator

60K views 27 replies 26 participants last post by  I M Legend 
#1 ·
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.

-Thanks.

 
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#5 ·
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.
 
#6 ·
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 .
 
#13 ·
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.
 
#15 · (Edited)
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.:clap:
 
#18 ·
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.
 
#21 · (Edited)
OP A million thanks for posting this. Excellent work!!!


I referenced this DIY yesterday and it was spot on! had my phone handy and went step for step. Absolute easy job and can't imagine paying the $700 my indy shop wanted. took me a less than 2hrs. I will also add that i opted not to remove the Oil lines and just swiveled the alternator around a bit until it came off. While i was in there i changed out the the AC belt too. If you forget the belt routing, there are pictorials online you can reference.

I bought a BRAND NEW Valeo Alternator (pn#439317 from ECS shipped for $275. No core needed as it comes shipped directly from Valeo but ECS is a distributor) and the AC belt cost $18 from JMK BMW

14 Volts back to the battery! Wheeeew
 
#22 ·
Just completed this DIY. Thanks for the great post. I changed:

2002 e46 M3:

3 - tensioners/pulleys:
-One that was stuck to the top bolt of the alternator call the (idle pulley) $50
-One below the alternator called main drive belt tensioner $40
-One on the left side that holds the tension on the compressor belt called (serpentine accessory belt) $40

All were around $40 each at autozone. I would have gotten better brands but it was a last minute decision to replace them as they span freely and made noises, which means the grease has dried up and risk freezing in the future.

2 - Belts:
-One short belt (runs along to the compressor) called serpentine accessory belt. $20
One long one (runs the alternator side) called the main drive belt. $20

1 - Rebuilt BOSCH alternator was $157 and $77 core charge at http://eEuroparts.com. They ship a return label.


Saving $180 charged for labor by indy shop, I was able to use that money to purchase all the items above. My car now has new belts, pulleys, and working alternator.

NOTE: This alternator replacement solved my year long issue with EML light even after I changed the three TPS sensors (top and bottom of manifold, plus the petal) I would feel a few hesitations on the gas petal/car and the EML light will come on, but no LIMP mode, but the next time the car feels like that during the same trip, LIMP mode comes on.

No battery or alternator warning lights came on for me during the whole year this was going on. These last few days, everything on the dash just lights up and the car dies. (issue was the alternator wasn't working right and everything was running off the battery until it was totally dead.)

So happy the EML issue was resolved by the alternator replacement. :excited:_nr_
 
#27 ·
Positive cable stuck

Hi all. I'm not sure if anybody will see this, since the last post was a year ago, but let's give it a try anyway.

The 17 mm nut that holds on the positive cable is stripped. A 17 mm wrench turns on it, and I can't get a 16 mm onto the nut. I also can't get a good enough grip with channel locks.

I'm replacing the alternator with a brand new Bosch, so I don't care what happens to it. But I do care about the connector underneath. My idea is to break away the plastic around the nut to create space then cut the nut with a Dremel.

Then I'll replace the alternator and the nut. How does that sound? Thanks!

John.
 
#28 ·
Hi all. I'm not sure if anybody will see this, since the last post was a year ago, but let's give it a try anyway.

The 17 mm nut that holds on the positive cable is stripped. A 17 mm wrench turns on it, and I can't get a 16 mm onto the nut. I also can't get a good enough grip with channel locks.

I'm replacing the alternator with a brand new Bosch, so I don't care what happens to it. But I do care about the connector underneath. My idea is to break away the plastic around the nut to create space then cut the nut with a Dremel.

Then I'll replace the alternator and the nut. How does that sound? Thanks!

John.
Yes, that should work. If you cut the plastic surround away, it should give you enough space to get a better grip with some channel locks or an adjustable crescent wrench. Make sure your ground wire is disconnected from the battery.
 
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