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Old 11-21-2020, 02:28 PM
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N55 Vibration Damper noise

I've been chasing an intermittent noise from the belt on my 2012 X5 with N55 engine. I did the normal things first:

Changed belt and idlers - none had any resistance and turned smooth
Checked accessories - all turn smooth, no evidence of bearing issues, etc.

After doing this, it seemed the noise was less frequent, but still would do it sometimes. Then it went away for several months.

This summer, it came back, but wouldn't always squeal. Now, I can replicate it everytime. It only make the noise when the engine is hot. If allowed to cool to close to ambient, it won't squeal. Warm / Hot, it always squeals. If you rev the engine above 3,000 rpm it goes away and doesn't come back until you stop it and restart hot. It will repeat that pattern as many times as you want to start / rev up / stop.

So I crawled under with the engine cold and the vibration damper is clearly wobbling. Heated her up, restart and the noise is there. I can tell the noise is centered on the crankshaft area.

Here's a video I took that gives noise and the damper wobble.
Edit: couldn't get embed to work-

https://www.youtube.com/watch?v=19-B...ature=youtu.be

On my phone it is slo-mo and the noise is clearly timed with the wobble. On Youtube if you set it to 0.25 playback speed it isn't as easy to see the timing, but it's there.

So, it seems my vibration damper is shot and causing the squeal. Odd that it only does it hot and after revving it goes away until restart. I found one video for an F30 that seemed similar, but searching didn't show anything else. Maybe I just used the wrong terms?

Before I replace $650 parts, Is this a common or known issue?
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Old 11-21-2020, 09:50 PM
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I would get a close look behind for a tolerance issue. Feels like something scraping to me.

Did you say you took the video in slow motion? I'm used to much slower when I use 240 fps video on my iPhone.
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Old 11-22-2020, 11:50 AM
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Yes, I took it in slow motion on my iPhone. But when I export, it goes to real time.

Went back to look, I can't find any clearance or scraping on the damper / block, etc. Used a flex camera to look all the way around.

Also, I've never seen a clearance issue that disappeared completely after revving. I've seen loose belts do that, but the tensioner, belt and idlers here are new.

Here's a sound recording of the noise and it going away when revved. I recorded the noise under the hood, then walked to the drivers door and revved it to ~3000. The noise goes away and everything is smooth after that.
https://www.youtube.com/watch?v=zkXS...ature=youtu.be


Last night, I also measured the axial runout on the damper and it's 1.1 mm of runout. I can't imagine that's normal runout on a BMW pulley. Anyone else see visible runout like this?
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Old 11-22-2020, 12:09 PM
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Ok, did some more searching leaving out any model or engine codes and came up with this video that sounds exactly the same.
https://www.youtube.com/watch?v=WzTTm_nD6ro

Comments show some other cars having the same symptoms - noise when warm only at idle. Looking like crankshaft damper. Rubber looks fine, but I can move it some with both hands. From the runout and stiffness, I'm going to replace it. $500 seems cheap insurance; if the rubber turns loose bad things can happen.

I'll report back if it solves the issue.
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Old 11-22-2020, 03:15 PM
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N55 Vibration Damper noise

I have one in my collection of stuff. Have to see if it's the same part number I can sell for a lot less than new. If you can move with hands It's shot. I never even knew the thing was two part based on handling to remove and install.

Use real OEM to find the part # and see what other cars use the same part.

I can't remember what car it came off but I'm pretty sure the part number is stamped on.
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