Idler pulley failure? - BMW M5 Forum and M6 Forums
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post #1 of 5 Old 18th April 2011, 04:18 PM Thread Starter
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Idler pulley failure?

Has anyone ever experienced failure of the belt pulleys? Or indeed changed them.
It has been suggested some new engine noises I have could be a pulley on the way out and I'd be interested to know if anyone knows the symptoms of a pulley failure.


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post #2 of 5 Old 18th April 2011, 04:22 PM
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Examples of the noise you're getting, perhaps a vid? Or am I missing that you've posted this elsewhere.

I've had a pulley bearing collapse before, straight after a 300 mile drive, so they can fail over time. On my list.

I think when I priced these up, they're not too much, good to do them while doing the belts

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post #3 of 5 Old 18th April 2011, 04:55 PM Thread Starter
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I will see about sorting a video, the noise is a rattle at certain rpm which then turns into a metallic screech if left.
I was thinking the worst -> timing chain, but it was suggested it could be a pulley failing.


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post #4 of 5 Old 18th April 2011, 11:51 PM
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They fail... sometimes at 85 or 90 miles an hour, throwing the serpentine belt into the radiator fan in the process, destroying it. And taking the the water pump out at the same time, just for good measure. Bonus points for a fan blade happening to hit just right such that it cuts through the fire blanket and leaves a 3/8" dent in the hood. Spared the radiator.

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post #5 of 5 Old 18th April 2011, 11:57 PM
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It is probably best to replaced all the idler & tensioner pulleys when doing the belts. I see these type of failures all the time.

Real easy way to check is to get an inexpensive stethoscope & listen on the area the pulleys are bolted to. Just be careful not to hit the fan with the engine running!
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