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944 balance belt noise.

 
Old 02-04-2019, 05:07 PM
  #1  
Joseph Moon
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Default 944 balance belt noise.

Hello! New member here, and I'm sorry to start off on a really repetitive topic, but... Balance belt squeal... I've seen there's already lots of threads and I have looked through them but haven't really found an answer.

​​​​I've definitely identified my noise as the balance belt by putting a stethoscope on the tension pulleys, but no matter what I try the noise stays pretty much the same. I've got the belt running as loose as I'm comfortable with (you can nearly twist it 180) and I've adjusted the idler pulley with it running and no change. I've seen comments ranging from "there supposed to be noisy" to "different brand belts are quieter" and "it will brake in after time" I'm not really sure what to make of it. I wouldn't mind buying a different brand belt, but I don't want to go through hundreds to find they are all the same, so is there one particular brand that lots of people have had success with? Anyway I would be really grateful for any advice.
Thanks very much
Joe
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Old 02-06-2019, 09:13 PM
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951Tom
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On my car it seems the idler pulley is what makes the noise. I ran the motor without the idler and it's much quieter, almost silent. But I think without the idler pulley and the looseness of a properly tensioned belt, the belt can jump teeth & put the lower shaft out of alignment? Maybe someone can confirm this.

I'm adjusting my belt tension with the Arnnworx tool and setting the idler spacing with the factory P9207 tool and can't get it to run silent. The top span of the belt sits about 1mm above the idler pulley at rest.

My current belt is a Gates with about 10k miles on it so should be broken-in by now. The squeal/whirring does quiet down once the motor warms, but you can still definitely hear it. Next I was going to try a Continental and then a Flennor belt to see if any difference. The Dayco belt looks like the cogs are not rounded but in a trapezoid shape. I was wondering if anyone has used it.
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Old 02-08-2019, 01:47 AM
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mrgreenjeans
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I have only used the Porsche belts which have come in their boxes marked as Continental.

No squealing, no whirring if adjusted correctly. Pretty much silent.

The only time I had noise was when the original water pump on one began to leak coolant and at the same time the rollers became rough. After changing them all to new Porsche parts, the n/a was once again silent
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Old 02-11-2019, 02:18 PM
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Joseph Moon
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OK, thanks for the replies guys. I will try a continental belt next and report back. That noise drives me crazy!
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Old 02-11-2019, 03:51 PM
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Dan Martinic
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The best I can do is some whine at cold start--more so if it's been sitting more than a day--then quiet as it warms up with no further noise till it sits again.

This is with the roller touching the belt on the long span which is how I read that diagram:




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Old 02-11-2019, 10:38 PM
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whiggins
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I've used numerous Gates balance belts on the 944, 951, and 968. I've never had one whine if the tension was right. I use the Arnnworx tool.

Make sure you are turning the tension roller CLOCKWISE to tighten. It will tighten counterclockwise too, but it will make the belt whine. There is more information about that on clarks-garage.com.

.
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Old 02-17-2019, 08:24 AM
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Joseph Moon
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A lot of the directions I've read for belt say the idler pulley needs to deflect the belt by 1mm, which is how I had it before. So I've backed it off as far as it will go and it's just barely touching the belt enough to spin the idler really slowly when the engine is running. It is quieter and less annoying but still audible and doesn't get much quieter once its warm. I will still try the gates belt at some point still but I'm not in as much of a rush now as I'm confident it's causing nothing more than an annoying noise.
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Old 02-17-2019, 01:23 PM
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Dan Martinic
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This morning, I made quick videos of the balance belt noise both cold start and upon returning from a 10km run. In my opinion, these are normal amounts of noise--a part of many rotating noises in our beloved cars.

Same morning.

MORNING COLD START at minus eight degrees celsius overnight:



WARM ENGINE at minus five degrees celsius & following a 10km drive:

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Old 02-22-2019, 02:52 AM
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Joseph Moon
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Thanks for the videos Dan I really appreciate it. I'm surprised that you can't really hear the whine at all in the second video. Mine definitely doesn't become that quiet when it is warm.
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Old 02-22-2019, 09:14 AM
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As per factory service instruction, the idler pulley on the long stretch should have pre-load on top--not a gap:




This is consistent with the drawing I added earlier. I install it fairly loose overall. I set the credit-card gap on the bottom and touching on top.

I too couldn't get rid of whine until I followed the above procedure. Most common idea is to leave gaps on both ends and I feel this is wrong.

The first video's whine is a worst-case: sitting over 12 hours and ambient temp quite cold. This morning, after getting home late last night and with plus one deg C outside, I can't remember hearing anything.
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Old 03-10-2019, 12:26 PM
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Thanks for posting Dan! I'm gonna set the idler the way you posted. One thing I'm wondering, when you set the idler spacing, did you have tension or slack on the upper span of the belt? This would appear to effect the height of the belt to the idler at rest, thus effecting the adjustment? (Sorry for the delay in posting, got side-tracked with some other repairs but back to the b/s belt whine.)
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Old 03-10-2019, 12:50 PM
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It's been a while, so I forget exactly if the top span sagged or not. I doubt it; though I set it pretty loose, I think it still stayed straight on top. If there was a bit of sag, that's probably where the pulley pushed it back. Sorry can't be more detailed
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Old 03-12-2019, 01:01 PM
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I am pretty sure I use continental as well. I always get belts from ian at 944online. I follow Van's u tube video on a 951 but the same process on all cars. If you check your rollers ( spin by hand ) if noisy replace. My car sounds the same as this videos posted so you know what your trying to get.
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Old 03-12-2019, 05:11 PM
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951Tom
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I set the idler pulley (using the P9207 tool) so it just barely pushes up on the top span of the belt a little. I did the adjustment after turning the crankshaft a bit to take up any belt slack and I'm still getting some whine. It's not bad, but it's not quiet either like in the above videos. On other threads, some have posted that the whine goes away after driving awhile so I'll report back. I measured the thickness of the P9207 tool to be about 0.75mm (give or take a few hundredths).
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Old 03-12-2019, 05:41 PM
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It'll loosen a bit over the next couple of days... then it should quiet down
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