Belt Tensioner

Mark963 · 10-16-2018, 10:26 PM

I apologize for being a newby on this. I've found picture of REALLY badly worn tensioners (with the belt about to fall off) but I'm just wondering where exactly the serpentine belt is supposed to ride. Is it OK if just near the edge of the pulley? I'm questioning a whining noise that the car makes at low RPM and noticed this looking pretty close to the edge of the pulley.

Thanks,
M

hugus311 · 10-17-2018, 12:17 AM

That is normal. I would replace the belt tension er and idler pulley if your over 150k miles.

CTinline-six · 10-17-2018, 09:10 AM

That's normal. If the belt is coming off the edge of the pulley then it needs to be replaced.

desertman123 · 10-17-2018, 02:37 PM

Take the belt off and spin each pulley by hand.

Also the timing chain is a little noisey, don't get the sound mixed up

Mark963 · 10-18-2018, 01:34 PM

Quote:

Originally Posted by desertman123

Take the belt off and spin each pulley by hand.

OK!

The tension pulley turned smoothly and stopped immediately if I flicked it. The other pulley to the right would spin for seconds. I'm not sure if that's OK.

The steering pump turned pretty smooth, but make odd click/clack sounds as it changed direction when turned.

The alternator was turned with a lot of drag on it.

I guess that's all normal.

desertman123 · 10-18-2018, 03:43 PM

Quote:

Originally Posted by Mark963

OK!

The tension pulley turned smoothly and stopped immediately if I flicked it. The other pulley to the right would spin for seconds. I'm not sure if that's OK.

The steering pump turned pretty smooth, but make odd click/clack sounds as it changed direction when turned.

The alternator was turned with a lot of drag on it.

I guess that's all normal.

The idler should have a little bit of drag in it. If it spins very freely that means the grease inside the bearings has escaped.

Everything else is normal. You're just feeling the pump itself turn, alternator clutch, etc.

mckwong · 10-19-2018, 04:27 PM

On my 60k miles E90, the dealer found the belt tensioner pulley is crooked during an inspection. I changed it myself. Easy DIY. When I inspected the old tensioner, I noticed the gap between the center plate and the housing is not uneven (one side is much closer than the other). Maybe you want to take a look of yours to see if you have the same issue.

10-16-2018, 10:26 PM	#1
Mark963 Private 32 Rep 79 Posts Drives: 2011 328i Join Date: Jun 2018 Location: Iowa iTrader: (0) Garage List 2011 BMW 328 [0.00]	Belt Tensioner - What's Normal? I apologize for being a newby on this. I've found picture of REALLY badly worn tensioners (with the belt about to fall off) but I'm just wondering where exactly the serpentine belt is supposed to ride. Is it OK if just near the edge of the pulley? I'm questioning a whining noise that the car makes at low RPM and noticed this looking pretty close to the edge of the pulley. Thanks, M Attached Images
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10-17-2018, 12:17 AM	#2
hugus311 Titanium silver + Sport + Premium 32 Rep 662 Posts Drives: 2006 330i (E90) Join Date: Nov 2009 Location: west covina 626 iTrader: (6)	That is normal. I would replace the belt tension er and idler pulley if your over 150k miles.
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10-17-2018, 09:10 AM	#3
CTinline-six Hoonigan 6947 Rep 3,017 Posts Drives: '09 328i, '98 Wrangler Join Date: Dec 2016 Location: Connecticut iTrader: (0) Garage List 2009 BMW 328i N51 [0.00]	That's normal. If the belt is coming off the edge of the pulley then it needs to be replaced. __________________ "Yeah, but your scientists were so preoccupied with whether or not they could, they didn't stop to think if they should." -Dr. Ian Malcolm, Jurassic Park
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10-17-2018, 02:37 PM	#4
desertman123 E82 Mudflap Ambassador 2244 Rep 2,220 Posts Drives: '08 128i Join Date: May 2016 Location: Orlando, FL iTrader: (0) Garage List 1992 Honda Beat [9.50] 2008 BMW 128i [10.00] 2014 BMW 528i [10.00]	Take the belt off and spin each pulley by hand. Also the timing chain is a little noisey, don't get the sound mixed up __________________ My 2008 128i - Sparkling Graphite/Beige - Sport pkg - 6MT - Click me! Parents' 2014 528i - Mineral White/Ivory White - fully loaded Instagram @Andreys_128i and @Honda.Bito
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10-19-2018, 04:27 PM	#7
mckwong Private 12 Rep 61 Posts Drives: 2009 328i E90 LCI with N51 Join Date: Feb 2016 Location: Fremont, CA iTrader: (0)	On my 60k miles E90, the dealer found the belt tensioner pulley is crooked during an inspection. I changed it myself. Easy DIY. When I inspected the old tensioner, I noticed the gap between the center plate and the housing is not uneven (one side is much closer than the other). Maybe you want to take a look of yours to see if you have the same issue.
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