"RallyWrench" (rndlitebmw)
06/18/2015 at 18:38 • Filed to: BMW, HOW THEY FAIL
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"RallyWrench" (rndlitebmw)
06/18/2015 at 18:38 • Filed to: BMW, HOW THEY FAIL | 5
| 8 |
Here we have an example of the ubiquitous BMW N-series engine, and a common failure point (among others), the serpentine belt tensioner. This one was too good an example not to share. When they lose the belt, they tend to wrap it around the crank pulley, and can push in the crank seal, suck the belt into the engine, and starve it of oil pressure. I’ve not seen one do that, but that’s what happens when this goes too far according to BMW and other independent shops I’ve spoken with. These fail all the time, with the tensioner vibrating and deflecting to such a point that it breaks the aluminum bolt holding it to the engine, which causes the belt to walk off the pulley. They usually give fair warning if you look under the hood once in awhile, with the belt deflecting just slightly. This car just came in for an oil change, no mention of noises or any other indicator of failure. It likely would have been on a tow truck within a few miles had it not, so he got lucky!
Twingo Tamer - About to descend into project car hell.
> RallyWrench
06/18/2015 at 18:43 |
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Damn that’s one lucky guy. I wonder if it was running badly too, surely the timing jumped a tooth with that much movement.
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RallyWrench
> Twingo Tamer - About to descend into project car hell.
06/18/2015 at 18:45 |
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It’s a chain driven engine, that’s the accessory belt. Still a potentially catastrophic failure if it starves the engine as described.
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Twingo Tamer - About to descend into project car hell.
> RallyWrench
06/18/2015 at 18:49 |
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Ah I see, I should’ve read properly haha.
DoYouEvenShift
> RallyWrench
06/18/2015 at 18:54 |
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Next gen will have a belt tensioner angle warning light.
T5Killer
> RallyWrench
06/18/2015 at 18:55 |
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Wow that is wild. 94-95 5.0 Mustang had a similar issue with the balancer coming apart (it was two part unit with rubber in between) they would come apart and cause all kinds of havoc.
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RallyWrench
> DoYouEvenShift
06/18/2015 at 19:09 |
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I would not be at all surprised. 964 Porsches had a fan belt deflection sensor with attendant warning light on the dash 25 years ago.
AM3R shamefully returns
> RallyWrench
06/18/2015 at 19:58 |
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No kidding, just installed a Microfilter on the e90 and looked around the engine. Changed the tensioner 2 months ago just cause I had a spare one and a ton of free time.. Everything looks good!
samssun
> RallyWrench
06/18/2015 at 20:15 |
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I think the point was less the belt, and more that they view another sensor and warning as a better fix than redesigning it not to fail that way in the first place.