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DIY Alternator replacement e46

118K views 74 replies 51 participants last post by  TR4G- 
#1 ·
Ok, this is how i did mine, i hold no reliability on my install...so you cant sue me! The stealership gave me a quote from 888-1047.



TOOLS NEEDED:
Socket Wrench
3inch Extension
12mm 16mm 17mm 19mm
Pliers

First you take off your airbox.


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After you take off the 12mm bolts and random plastic screw things this is what you'll see.


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Once those parts are off disconnect the power from your top left corner of the engine bay. I believe it was a 12mm bolt.


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Once you disconnect that power wire, disconnet the power wire on the alternator itself.


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Next, undo the long bolt that is connected through the alternator.


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After thats done, take the cover off from the pully thats attatched to the alternator. I believe its a 16mm bolt.


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Closer look of the bolt you just took out.


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Next get some pliers to hold the other pully firm so you can give slack to take off the belt.


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This is what it should look like with your alternator off.
http://i26.photobucket.com/albums/c134/10bmw10/Picture011.jpg

Put the 12mm bolts back
http://i26.photobucket.com/albums/c134/10bmw10/Picture012.jpg

Put the plastic back
http://i26.photobucket.com/albums/c134/10bmw10/Picture013.jpg


Last reassemble the power wires! Follow your steps and its easy, it took me less than 40minutes to do, and ive only had the car less than 5days.

Thanks for reading, Brian
 
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#5 ·
I saw the tensioner afterword, it makes it alot easier when you find that. I wasnt really wrenching, i just made sure it was steady when i pulled off the belt. When putting the belt back on, people will notice the tensioner and their life will be easier.

thanks for the compliments, im sure theres a more professional way out of a book, but i just winged it and it worked perfectly. Just make sure the belt is in the grooves!!!
 
#7 ·
You're not going to want to hear this, but hit it with a hammer. seriously. Don't wail on it, just give it a good smack, and it should move a bit. Then you'll need to either rotate it a bit and hit it in the same direction, or hit it from the other direction.

I haven't changed the alternator on my 323i yet, but I've had to do this on every alternator I've replaced in the past (Sebring, Grand Prix, Dakota, Camry). They're fairly tight when they're new, add just the tiniest bit of corrosion and they're a pain to get out.
 
#9 ·
I did mine at 131,xxx miles as preventive maintenance. I replaced my originally installed Valeo with the Bosh. I did notice that the new alternator handles better the electrical load (heated seats, xenons and all interior lights on). Oh and The bosh alternator came with the voltage regulator already installed.
 
#10 ·
thank you, you're a life saver. I was just stranded on the freeway not too long ago and I'm pretty sure it's my alternator as my battery light kept flashing until my dash lit up like a xmas tree and the car shut off at 65mph. Luckily, I was able to roll to the side of the road. I flatbedded my car home and I'm now sourcing out alternators.

I hear alternator replacement at the dealer is $1k++
 
#11 ·
I'm doing mine now and it so far, I've managed to extract the alternator. I'm having problems putting in the new one because the bottom brackets on the new alternator has really tight tolerances. I'm sanding down a little bit of the bracket mounting points so I can slide it in easier.

btw, M3's are a pita because there are metal oil lines right above the alternator.
 
#12 ·
I just had my battery up & die on me. My friend ran an electric test on the car, the test was that the alternator was ok. Battery is deaded, off to the parts store tomorrow!
What year is your car? what milage are you at, wondering if I should start looking for an alternator too, just incase. I am at 34,XXX
 
#14 ·
Probably a 90A alternator

My guess is the chap that wrote this DIY was replacing a 90A alternator and not the 120A that's in the 330i/ci as I am into this repair myself and have discovered the *other* bolt. From talking to a friend with the maintenance manual the fan and fan shroud have to be removed to gain access to that second bolt. It may be possible to get it out without removing the fan but you'd need hands smaller than mine. I'm off in search of the requisite 32mm wrench required to remove the fan bolt (which by the way is threaded backwards - righty-loosy). If there's any sanity left at the end of this I may post an update.
 
#17 ·
I just wanted to toss a few lessons-learned out there for those that consider the DIY alternator change.

1. It is a very doable DIY job so don't fret. My process and setup was different from the original authors and yours will probably be different than mine.

2. If you have the mechanical fan (connected to the water pump) take that out first. It may be possible to do it with it in but after fighting it for a day and then taking it out I could've saved myself hours on the job. There are some good articles out there on removing the shroud and fan. As I find them again I'll post them here.

3. Apparently not in all, but some alternators have 2 mounting bolts, not 1 like the original author of this post. Not sure what the rule is there but I'm sure someone does.

4. Tools - you need a special tool to hold the pulley on the water pump so you can remove the 32mm bolt that attaches it to the fan. You can buy this (@ bavauto for $40) or you can make it like I did. I'll post a pic later. In addition, have a good selection of metric sockets. I recommend 5mm-19mm, 3/8 drive, a 3 inch extension, and a breaker bar - you won't use all of the sockets but you'll thank yourself later for having them. You'll need a 32mm wrench (mentioned above and also for sale at bavauto for yet another $40) but I couldn't find one quickly so I used a crescent wrench that opens to 35mm - 10" cresent. Lastly, to de/re-tension the belt, you'll need a T50 torx wrench. I got the kind that connects to a 3/8 drive wratchet.

5. Before you start draw a quick little map of the belt's path around the pulleys. You think you'll remember but if it's your first time, and after a few hours in the hot sun and a few beers you'll question yourself as you put it back on.

6. I'm surprised that there isn't more information on alternator replacement on this forum but perhaps it's such an "easy" thing to do that no one feels it noteworthy. A newbie like me could've used more detail. The good news is that it's out there, in other posts and forums under searches like "water pump replacement", "belt replacement", etc.
 
#72 ·
That God damn fan.. is where I'm stuck at.

Other thing to note is I've been told to remove the upper hose.

If you're a newb like me, doing that was tricky where i managed to break the tabs off the thermostat so now the hose sits but not securely. Just as well, buying myself a new thermostat right this minute. Silver lining I suppose, one thing less to do next time around.
 
#18 ·
BTW, I was at 80K miles and I got the alternator at the stealership because I needed it ASAP (on a Saturday) and none of the local parts stores had one. I paid $370 including $30 core. My stock alternator was the Valero 120A. You can get this for much cheaper elsewhere if you have the time.
 
#20 ·
10bmw10 and t-papa good writeups!
 
#23 ·
It took your mechanic three hours? Did he charge you for that too?

Yikes! Granted, ///Mechanic has lots of experience, but even for a backyard mechanic like me three hours is crazy. I think it took me right around an hour.

(I think the BMW Flat Rate is around 50 minutes)
 
#25 ·
I wasn't sure how labor intensive this was going to be, but I had a friend that told me it was simple... he told me that according to some program (KDS? KSD? LMNOP?) that the time factor was around 50 minutes.

He may have had the time info all wrong, but it did go rather smoothly and quickly. Maybe part of the difference is that the fan is very easy to pull on a manual tranny set-up.
 
#28 ·
After reading all the postings in this thread (thanks for all the valuable info!), I went ahead and replaced the alternator in my 328ci over the weekend after it left me stranded the other night. Here's a couple of observations from my experience; yes, this is a very doable diy, but there are few variables that could affect how doable it is for your situation, as well as how long it will actually take.

Removing the radiator fan makes this job a lot easier (allowing more room to work), and is essential if you have the 120 amp alternator (328 and 330 from what I gather) because it has bolts on the top and bottom. In my case there wasn't even enough clearance for the alternator's long top bolt to be removed before the fan started interfering with the ratchet handle.

Another variable: Apparently automatics have clutch fans while manual's have electric. This can make a big difference because the clutch fan can be very difficult to remove without the special BMW tools that hold the water pump pulley in place while you unscrew the 32mm nut that holds the fan on. I ended up sacrificing a long, skinny screwdriver to wedge the pulley while I leaned on the wrench to loosen the nut. I now have a nicely curved Craftsman screwdriver, but it did the job after numerous attempts. An electric fan would've been much less trouble to remove.

Once the fan's out it's easy to get to the alternator's bolts and belt. However, in my case, after removing both bolts it took another 20 minutes of using a prybar and rocking the alternator back and forth to free it from its mounts. Also, for some reason the Bentley manual includes the completely unnecessary step of unscrewing the two bolts that hold the plastic air duct to the back of the alternator before pulling it out. The bolts (7mm I think) are hard to get to and nearly impossible to see, which makes them frustrating to remove. There's no reason whatsoever to do this-- it's not in the way of anything and the replacement alternator already had it attached. Go figure.


Next variable: some vehicles have hydraulic belt tensioners which require an allen wrench to move, while others have mechanical tensioners which can be moved quite easily by turning a 16mm bolt to rotate the tensioner.

While you're in there, consider replacing the belts. One of mine was starting to look tired so I just replaced them both. They're easily accessable and for $35 it's something I'd rather do now than have to take everything apart again to do later. Just remember how to route the belts around the pulleys and tensioners --a diagram helps-- and make sure the belts are properly seated in the grooves on each pulley.

Assembly is simply the reverse of disassembly. I was pleasantly surprised that the new alternator slipped perfectly into the mounts and the bolts went in with no problem. I was expecting an argument.

In total, with my clutch fan, and 120 amp, two-bolt alternator, mechanical tensioners and time wasted removing the duct, it took me about 3.5 hours to to get at and remove the old alternator. That included a trip to Sears to get a 32mm wrench (about an hour) and probably an hour trying to get the fan out. Your mileage may vary depending on the variables listed above and whether or not you have the proper tools on hand.

Installing the new alternator and new belts and putting everything back together took way under an hour.

The local stealer wanted $950 to replace the alternator, not including changing the belts. My total cost for this diy was $245 for the 120 amp Bosch alternator from a local parts place, $35 for the two belts, $26 for a 32mm wrench, and a few hours of time getting intimate with my vehicle.

What could be better??
 
#29 ·
I have one question...I keep on hearing that automatics come with clutch fan. That's not the case for me. I have a manual 323 that comes with the clutch fan. Could it be that my car was originally automatic but changed over to manual. Please someone clearify. Thanks.
 
#30 ·
Bosch and Valeo 120 Amp Alternators

I was under the impression that the Valeo and Bosch 120a alternators on the 323I's are not interchangeable. Am I now finding out that I am wrong?

I am tried to find an alt here locally and have passed over several Valeo units. Does this mean that I actually COULD have used them?? I'd prefer Bosch but... I could live with VALEO

THX
Tom
 
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