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Discussion Starter · #1 ·
Just bought a 2010 X5 35D, about 138k miles. I started hearing a squealing sound when accelerating - seems to happen between 1.5-2.5k RPMs. Only under load, can't reproduce in neutral (making it hard to pinpoint where it's coming from). Originally though it was lower intake boot but since can't reproduce in neutral, thinking it's something else.

It's not the turbo siren some have mentioned before, and happens much more when engine is cold. Noticing more now that temps are getting lower. Also have some exhaust smell in cabin at cold start, but not sure that's related.

Any ideas? Will post a video of the sound soon.
 

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Discussion Starter · #4 ·
Thanks for the replies so far folks, here's a video of the sound for more clarity. You'll see it gets pretty bad from 1.5k rpms up to about 2k. Worse when cold (this was early in the morning).

 

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Nuclear engineer
02/2012 X5 35d M57Y CPO 121K miles NOKIAN WR G3 30K miles
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I don’t know how your cold[er] today compares to cold yesterday. Cold shrinks ‘rubber’ element in vibration reducer. Cold may increase accessories‘ load on accessory drive belt depending on your settings and actions.
 

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There have been two cases of harmonic balancer being the culprit of similar sounds in the past couple months on xoutpost.

Oddly it was the opposite where it made noise when warmed up vs. when cold.

See on real OEM if your engine shares the crank pulley with M62 motor I think I have a spare and can sell for less less than a new one.
 

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Are you saying the diesel model has a solid crank pulley? If that's the case, remove the serpentine belt and confirm the sound goes away.

If it does one of the serp belt accessories or pulleys likely has a bad bearing. You may be able to tell which with a manual spin.
 

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It's a guess, of course, but I'd give it a 95% chance that you have a missing exhaust manifold stud. Your video brings back memories. You can read about my experience in this link.

Your sound is just like mine, and the one I linked to in the post above. And it's complete with exhaust smell. You have to look carefully since the exhaust manifold bolts are behind a bunch of stuff. I used plumbers gas leak detector bubble solution (here is a link to the Oatey product) sprayed around the exhaust manifold and could see bubbles coincident with the revved engine and squeal. Hopefully your missing stud bolt will be in one of the two most forward positions which allow drilling out and replacing without removing the lower turbo and exhaust manifold.

Good luck, let us know what you find.
 

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Another link that is likely to be interesting reading is here. This fellow also had at least a missing exhaust manifold stud. As is discussed in that post, you also may have multiple issues. If you have a squeal around 2000 rpm, I think it is very likely that you have a missing exhaust manifold stud. If that is the only time you have an exhaust smell, then that may be your only issue. But if the exhaust smell is present even when you are at much lower rpms, then there are multiple places to check for possible exhaust leaks. Post #22 of the link discusses several places that have had leaks in the past.

Again, good luck and let us know what you find.
 

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stag21 disappeared after his last post...

Its apparently a thing.

;)
 

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I think it was the upper mounts of the front struts. I know it sounds weird but I just sprayed WD-40 on top to the strut mount and the sound will go away for a few months. I think the rubber has decomposed. BMW used a lot of crappy polymers in their vehicles.
 

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I think it was the upper mounts of the front struts. I know it sounds weird but I just sprayed WD-40 on top to the strut mount and the sound will go away for a few months. I think the rubber has decomposed. BMW used a lot of crappy polymers in their vehicles.
Good test.

A tell-tale is to look for light brown 'dust' around the top of the mounts.... rubber bushings getting ground up....
 
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