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Keif 06-03-2012 11:46 AM

Alpina B7 supercharger chirping/pulley wobble - clutch/bearings
Car: 2007 Alpina B7 / 70k miles
Relevant history: Centrifugal clutch on supercharger replaced around 26k miles several years ago.

Since I bought car a week ago there has been a metal-on-metal chirping. It has gotten more frequent with each day, then a few mornings ago it sounded HORRIBLE, like an index card in your bicycle spokes. I pulled off a small cover and saw the supercharger pulley wobbling in time with the chirps and clangs.

So, I started pulling it apart. Pictures and descriptions are in the link below, but I'll describe a little bit here, too.

Normal centrifugal clutch operation: (a more comprehensive training document on the Alpina B7 can be found on /
The belt-driven pulley is bound to the inside portion of the supercharger's clutching mechanism, which can be best described as drum brakes where the outside belt-driven pulley acts like an axle or wheel, which normally spins freely. Once the pulley spins up to about 1,100 rpm, the centrifugal force begins to push the clutch shoes out against the "drum", beginning to lock them together. This inner "drum" is what actually spins the supercharger.

Problems that I've seen so far:
In my pictures you can see that while the centrifugal clutch shoes have plenty of life left on them, a ball bearing and spring have come out of place. These normally help keep proper spacing between the metal pulleys, plates, and clutching components. In addition, there is an inner bearing or spacer that the pulley and clutch assembly rotate on. This bearing was fairly stiff when attempting to wiggle at any angle but one. The bearing wiggle at this one sloppy angle definitely caused the scoring seen in the various pulleys and plates.

Resolution / fix:
I ordered some sort of unlisted supercharger / radial compressor clutch rebuild kit from a local dealer, part number 11-6-57-973-081, for around $952 after taxes. They did not have any diagrams for this, so they could not confirm that it had the parts I needed, but they believed this to be what I needed and got the part number from the supercharger clutch recall repair previously done at 26k miles. I will post more pictures and info about this once the kit comes in.

Kit came in and DID include all parts needed. Used gear-puller tool included in kit to pull clutch/bearing off and press the new assembly back on...process was fairly smooth.

Time required:
Took one evening going very slowly and taking lots of pictures.

See pictures, videos, basic steps, descriptions --> here.

Keif 06-03-2012 11:47 AM

Labeling / descriptions on pictures and videos complete. Supercharger working perfectly now.

lendog15 06-24-2012 04:06 PM

I love reading posts like this. Not that I would even ATTEMPT to do something THIS detailed but I guess I'm a sucker for happy endings when it comes to an issue most would chalk up to "NEVER TRYING THIS DIY DEAL..." which is sort of me.

Thanks for posting.


Hossy 07-19-2012 09:46 AM

Very well done, Keif - this just happened to my B7, almost at identical mileage and with the same issues. Fortunately warranty is replacing the entire supercharger, but great to know that a full replacement is not always necessary in the future. Very nice detailed step-by-step pics and vids!

Keif 07-19-2012 01:36 PM

Gracias! =]

fieldydwb 01-13-2014 11:59 AM

Having the same issue.

Keif, where did you order the kit from? I am thinking of doing the same thing.

Is it a difficult process?


dadasaab 04-21-2014 04:18 PM

Hey Keif,

Were you able to figure out why there was oil in the intake of Supercharger?

ados 05-14-2014 08:11 AM

Hey Keif, could you please provide map for this supercharger. We are going to install it to m50 engine and need this for calculation. Thanks in advance.

F-Tar 06-12-2014 12:40 AM


Originally Posted by dadasaab (Post 8292155)
Hey Keif,

Were you able to figure out why there was oil in the intake of Supercharger?

Crankcase ventilation.

Nice description!

Sent from BimmerApp mobile app

SeeYal 06-12-2014 04:34 AM


Originally Posted by Keif (Post 6961242)
Gracias! =]

Keif, glad to hear you sorted this out... Nice work!. No issues on mine yet...:thumbup:

Where are you located in Houston? Let's get together once after work... Bayou City and I go once a while enjoy some refreshments after work at Nextdoor Cafe on Memorial west...

Iwo 09-10-2014 10:11 PM

I have a question regarding the B7. I'm looking in to buying 2008 750i or the 2007/08 B7. I'm curious if the B7 is more challenging to work on then regular 750i ? Is the supercharger prone to failures ? Has the 4.4 in the B7 have tendency to leak like 745s ?
I know it's a little different from regular 4.4 and I know the 4.8 in the 750 is pretty reliable...
I'm not a BMW newbie.. ( on my 7th bimmer now) and I'm mechanically inclined plus I have access to parts so I'm not afraid of 7s :-)
Thank you in advance for any input !!!

ssmokn 10-10-2014 03:58 AM

Well done!

transporter1740 10-13-2014 07:29 PM

4.4 turbo
Google Bentley Arnage

MontanaRob 12-19-2014 10:27 PM

Great write up thanks!

TPIOlds 01-12-2015 09:09 PM

This may be a little off topic.

Is there any one here that would like to sell the old clutch assembly.

Please let me know

MontanaRob 11-30-2015 07:07 PM

FYI time to replace mine. I searched hard and found a complete repair kit for $619 including shipping from BMW of Fairfax VA. They have a special on parts via online order.

F-Tar 08-18-2016 05:49 AM

Anyone experinenced oil filling up the intercooler?

Seems like my charger is leaking from inside housing then oil blows into the intercooler!

How can oil get inside the housing?

MontanaRob 08-23-2016 07:18 AM

From my understanding, it is fairly normal for the sc to pull small amounts of oil in from the intake vent tubing just upstream of the blower and blow it through the intercooler and burned up in the engine.

F-Tar 08-23-2016 12:49 PM

Alpina B7 supercharger chirping/pulley wobble - clutch/bearings
2 Attachment(s)
Really? :O

Drained it 3 times already..

This is 6 days ago.. Attachment 574063

And this is just now.. Attachment 574064

Earlier this year i had problem during MOT.. High CO emission and lambda 0,97 (rich) normally lambda should be 1 to 1,03

And that got me figuring when draining IC the first time that MOT problem was cus engine was sucking oil and made the emission go crazy aswell as lambda.

I mean, that much oil going in and thru IC then into the engine cannot be good. Have any of you drained yours? It cannot be healty when IC gets full of oil in just 6 days :O

It feels unlikely that CCV can spit that much oil into the supercharger housing, or am i wrong?

MontanaRob 08-23-2016 01:06 PM

Really don't know. I've never drained mine. But anytime I take the intake snorkel off the blower, you can see a little pooling of oil from the CCV tube connection. Also, I've taken out the temp/pressure sensor from the intake, mounted in the metal elbow of the intake piping just before the secondary butterfly valve, and it it always coated in oil but operating fine. So that means oil is making its way to the engine. 163k miles and running strong :)

F-Tar 08-24-2016 03:45 AM

Can you please maybe drain IC on yours? Easy job!

Yes i have seen that little spot of oil after throttle body even when i bought it 3 years ago.

Mine is def coated in oil too! It has 175k km.. Runs so smooth, all in order. But this oil is kind of worrying! I did top up 1l of engine (max on stick) oil 2 months ago and now dipstick is on half.

And its running a litte rich might be cus its sucking oil into the cyl :/ but i have no solution in this

spencermcgee 09-22-2016 12:05 PM

Just installed this kit on my boss' Alpina. We used it to fix the rattle issue at idle in the super charger. Wasn't difficult to install at all and definitely a cheaper option than a full rebuild.

bsw357 11-29-2016 08:53 PM


Originally Posted by spencermcgee (Post 9850157)
Just installed this kit on my boss' Alpina. We used it to fix the rattle issue at idle in the super charger. Wasn't difficult to install at all and definitely a cheaper option than a full rebuild.

That kit on ebay is consist of inferior generic bearings and cheap O-rings.
You should replace the bearings again on your boss's Alpina at the first sign. Those inferior bearings won't last nearly as long as the original. There are some better choices on the bearings available for sure. HNBR O-rings or even better yet Silicone O-rings will be a nice touch.

Vip9700 11-29-2016 11:39 PM

Supercharged b7
I am looking for supercharged b7 alpina 2006 where can I found one

bsw357 11-30-2016 12:00 AM


Originally Posted by Vip9700 (Post 9948172)
I am looking for supercharged b7 alpina 2006 where can I found one

These North American E65 based Alpina B7s were only available for 2007 and 2008 model years.
There are a several of them listed on , or maybe on ebay. I had to travel to NYC area to pick mine up a several years ago. For some reason hot areas for these Alpina B7s are NYC area, Chicago area and Dallas area.
Good luck with your search,

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