Drive belt came off. ??!!??

Mountain_Commando · 03-04-2018, 02:27 AM

Hey guys,

Got a 'charging fault' error late last night after a long drive. Got it again this morning as soon as I turned the car on. I figured the battery was stale/needed charging, so I drove around normally. Noticed that the AC wasn't cooling.

Then got couple more warnings that battery was low and not charging, so I figured I should get home asap and then call in a mobile mechanic. On my way home, got a hard steering error and then a transmission warning and then the car started limping...managed to make it to my street 100 meters from my garage before the battery completely died.

So roadside assistance came over. Jump started the car and moved it to a parking spot. But battery wouldn't charge at all, car would die immediately upon removing the charger. So roadside assistance looked under the hood and found that the drive belt (or whichever belt runs the alternator) had completely come off!!!

No cracks, no damages to the belt whatsoever, it just clean came off. Any ideas what might have caused this? And should I take it to a BMW dealer, or just have a mobile mechanic come over and pop the belt back on?

Cheers.

floydarogers · 03-04-2018, 03:36 AM

Quote:

Originally Posted by Mountain_Commando

...

So roadside assistance looked under the hood and found that the drive belt (or whichever belt runs the alternator) had completely come off!!!

No cracks, no damages to the belt whatsoever, it just clean came off. Any ideas what might have caused this? And should I take it to a BMW dealer, or just have a mobile mechanic come over and pop the belt back on?

You need a new belt; don't put the old one back on (except to get it to a shop).
Doesn't have to be a dealer. Also, new tensioner - might be the reason it came off.

rak299 · 03-04-2018, 12:51 PM

There has to be something broken. The belt won't stretch enough to come off all at once. If it were that loose, it would have been squealing so loud you would have sounded like an ambulance. Maybe the tensioner or an idler mount. This is why god invented tow trucks.

_bdiddyb_ · 03-04-2018, 09:38 PM

Only way for it to come of is the tensioner.

Mountain_Commando · 03-05-2018, 12:40 AM

Quote:

Originally Posted by _bdiddyb_

Only way for it to come of is the tensioner.

+1. That's exactly what it was. Has been replaced and the car is functional again.

Wonder if this is covered under BMW warranty? (car is 3.5 years old with only 32k on the clock) Mechanic thought this was normal wear and tear.

Orion4 · 03-05-2018, 09:54 AM

That is not normal "wear & tear" to have a tensioner fail at the early mileage. More normal is they get replaced when you do the belt probably in the range of 60K or more. I'm at 97K on the original belt and tensioner.

Marlinman · 03-05-2018, 10:53 AM

Bentley manual says every two years. I just replaced mine at 85K from the original. Always testing the fences.

Orion4 · 03-05-2018, 01:02 PM

My Bentley's states: "To reduce chance of belt failure while driving, replace belt every four years."

When replacing the belt that is a perfect time to replace the tensioner as well.

03-04-2018, 02:27 AM	#1
Mountain_Commando Lieutenant 303 Rep 366 Posts Drives: 435i Gran Coupe M-Sport Join Date: May 2017 Location: Brisbane, Australia iTrader: (0)	Drive belt came off. ??!!?? Hey guys, Got a 'charging fault' error late last night after a long drive. Got it again this morning as soon as I turned the car on. I figured the battery was stale/needed charging, so I drove around normally. Noticed that the AC wasn't cooling. Then got couple more warnings that battery was low and not charging, so I figured I should get home asap and then call in a mobile mechanic. On my way home, got a hard steering error and then a transmission warning and then the car started limping...managed to make it to my street 100 meters from my garage before the battery completely died. So roadside assistance came over. Jump started the car and moved it to a parking spot. But battery wouldn't charge at all, car would die immediately upon removing the charger. So roadside assistance looked under the hood and found that the drive belt (or whichever belt runs the alternator) had completely come off!!! No cracks, no damages to the belt whatsoever, it just clean came off. Any ideas what might have caused this? And should I take it to a BMW dealer, or just have a mobile mechanic come over and pop the belt back on? Cheers. __________________ 435i Gran Coupe \| ///M Sport Pkg \| 430hp \| MHD Stage 2+ \| BMS Intake \| Catless Downpipe \| FMIC \| Black Sapphire exterior \| 9H Ceramic Coating \| Black Anthracite interior \| 19" Black ///M Wheels \| Red ///M Brake Calipers \| ///M Steering wheel \| ///M Metal Pedals \| Alcantara dash panel \| Carbon Fiber trims and gear knob \| Angel Eyes LEDs \| Surround Cameras \| Spoiler \| Coded ///M iDrive, Mirrors, HUD \|
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03-04-2018, 12:51 PM	#3
rak299 Major 601 Rep 1,048 Posts Drives: 2021 M3 6MT Join Date: Sep 2016 Location: san francisco iTrader: (0)	There has to be something broken. The belt won't stretch enough to come off all at once. If it were that loose, it would have been squealing so loud you would have sounded like an ambulance. Maybe the tensioner or an idler mount. This is why god invented tow trucks.
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03-04-2018, 09:38 PM	#4
_bdiddyb_ Lieutenant 215 Rep 558 Posts Drives: 2013 335i Join Date: Aug 2013 Location: California iTrader: (1)	Only way for it to come of is the tensioner.
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03-05-2018, 09:54 AM	#6
Orion4 Lieutenant Colonel 481 Rep 1,572 Posts Drives: 2013 335i Sport Line Sedan Join Date: Aug 2009 Location: Melbourne, FL iTrader: (0)	That is not normal "wear & tear" to have a tensioner fail at the early mileage. More normal is they get replaced when you do the belt probably in the range of 60K or more. I'm at 97K on the original belt and tensioner.
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03-05-2018, 10:53 AM	#7
Marlinman First Lieutenant 101 Rep 316 Posts Drives: 2013 335i xDrive Join Date: Jun 2015 Location: MD iTrader: (0)	Bentley manual says every two years. I just replaced mine at 85K from the original. Always testing the fences.
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