07-03-2015, 09:34 PM | #1 |
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Alternator Drive belt
I did a track day at Sonoma yesterday and there was a new M3 there. During his second run, he got an alternator light. I checked to see if the battery or the alternator was bad. Battery was good and alternator wasn't putting anything out. Upon closer exam, the drive belt had failed completely for the alternator and AC. It appears that the water pump is a different drive belt which was a good thing for him. I think he attempted to drive home on the battery.
Anybody else hear about this kind of failure? I don't think he had very many miles on his car.
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07-05-2015, 10:10 AM | #2 | |
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07-05-2015, 02:01 PM | #3 |
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I saw an m3 at road Atlanta with the same failure. Yes the water pump has it's own belt so limping it home is possible. I wonder if this will turn into an issue like n54 cars that were shredding the power steering pump pulleys under hard acceleration.
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07-05-2015, 03:57 PM | #4 |
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You're forgetting the best part; half the time the belt gets sucked into the crankcase
Last edited by Shredicus; 07-05-2015 at 07:07 PM.. |
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07-05-2015, 06:31 PM | #5 | |
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07-06-2015, 11:14 AM | #6 |
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Interesting, so far I haven't had any issues but it would certainly suck to have it happen. May have to bring a spare belt just in-case.
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07-28-2015, 07:32 AM | #7 |
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alternator belt failure
I had an alternator belt failure, on-track, at LRP last week in my 2015 M4.
The warning came up on the iDrive screen about a battery recharging malfunction. Tested the battery, car on/off w/a volt meter, and it definitely wasn't charging. Can't see past the intake ducting under the hood, even w/a flashlight, to determine what's going on w/the belts (didn't know it was an alternator belt or other problem). Tried to limp home after fully charging the battery but the battery totally discharged. A few points: 1) When the Li Ion battery discharges, there is no residual voltage (as in a lead acid battery), so NOTHING functions, including your hazard flashers. I had my windows down and couldn't put them up. Can't access the trunk (no redundant lock cylinder), etc. Luckily a friend jumped me to get power (wouldn't start the car) so I could close the windows and access the trunk. A safety concern, as it was getting dark and I was on the shoulder of a 50mph road 2) The failure of the belt was due to an idler pulley bearing which damaged the alternator belt, I'm sure because of the idler pulley buinding, causing the belt to fail 3) I assume this happened on the track due to consistent high revs but also the fact that my car has 12,000 miles on it now (production date May 2014) and that may be as far as the idler pulley can make it. FYI - this was my third track day of the season. Belt/idler passed track check-out inspection and the shop checked the belts (although quickly, because the car is so new). This possibly should also be in the mechanical/maintenance/TSB section, also. Anyone else? |
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07-29-2015, 10:28 PM | #8 |
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How many miles did you go before the battery died?
Also, do you have the part number for the pulley that had to be replaced? I want to get spares in case it happens to me. Thanks
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03-16-2016, 03:53 PM | #9 |
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same thing
I just wanted to chime in and say that the same thing happened to me this past weekend. The idler pulley failed on my 2015 M4 in about the 6th lap on the first day I've taken it to the track.
Interestingly, like some of the other posters here it was one of the earlier production rolls (July 2014) of the model, so I wonder if that has something to do with it? Either way though, this is the first real issue I've had with the car in 1.5 years, and it's been a blast other than that. So don't let this scare you away from an amazing machine! 23k miles on this one, but I think it's the 1st track day more than anything that did it. |
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03-21-2016, 02:34 AM | #10 |
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so I guess I was the first one had this problem. I had this happen to me almost a year ago during the first trackday my M3 had, which odo just went over 3000km. Had it replaced under warranty and went to few trackdays after, so far so good.
The only difference is I had my a/c turned on when this happens, and I then always turn off A/C when I track the car. Just thought it might has something to do with the extra load? |
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03-25-2016, 04:20 PM | #12 | |
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03-26-2016, 02:24 AM | #13 |
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04-02-2016, 10:53 AM | #14 |
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Flying Low and Solace...Do you guys know the part numbers??? There are 2 idler pulleys, one of which is specific to the S55 while the other is on multi platform. Want to buy a spare of whichever fails along with belts to keep in track box...
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04-02-2016, 02:35 PM | #16 |
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09-12-2016, 10:48 AM | #17 |
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Thought I'd jump in and mention that I believe this happened to me this weekend. Same battery malfunction light came on the dash and belt shredded. Immediately pulled over and stopped the car to check everything out. Ended up having to call BMW assist to pick the car up and take to my dealership.
I noticed oil residue around the pulley's and found 2 small ball bearings under front of car. There was also a small oil drip coming from underneath the left side of the engine, which I could only determine would be from oil supply lines to the turbos. Could shredded belt pieces even effect or reach oil supply lines?......Dealership has the car now so waiting to hear their diagnoses and resolution. Car is a 2015, production date of August 2014 so one of the early models like others in this thread. Only 15,xxx miles |
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09-14-2016, 03:50 PM | #18 |
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Apparently this hasn't been much of a problem for the F8x platform or there would probably be a new part number in RealOEM. I can't find any new part numbers. I have a long background in aviation and auto maintenance and quality control. My guess is that this drive belt comes off very occasionally at the track. Under full throttle the AC probably turns off (drive clutch releases but I'm assuming that we still have a drive clutch in these new cars). At the track we are at redline but then we get off the gas and get on the brake. Now the AC clutch re-engages quickly as the RPM drops suddenly. There could be a sudden load change on the belt and tensioner in such a way that the belt comes off partially (ribs side step) or completely off. And that could lead to total destruction of the belt. I'm trying to remember to always run with the AC off.
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11-05-2016, 09:41 PM | #19 |
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This happened to me yesterday at the track. I was at 8900 miles, and missed half of the track day because of it. It was my 5th event in the car, and it's been solid apart from this issue. Having to get towed home was shitty.
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11-05-2016, 09:54 PM | #20 |
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Wow... Had no idea, such a shame b/c the S55 is a beast on the track. Might be a good idea for F8x owners to pack a spare belt to the track.
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11-06-2016, 01:36 AM | #21 | |
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11-06-2016, 05:47 AM | #22 |
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Was you A/C on or off when it hapenned?
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