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BMW 3-Series (E90 E92) Forum > E90 / E92 / E93 3-series Powertrain and Drivetrain Discussions > NA Engine (non-turbo) / Drivetrain / Exhaust Modifications > Whining Sound (Neutral)



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      07-19-2016, 04:25 AM   #1
AfteMath
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Exclamation Whining Sound (Neutral)

Hi, first of all I would like to thank the forum for accepting me.

That been said, let's get down to business.

I drive a Black 2008 e90 BMW 320i M Sport, love the car, drives real nice.

But recently I have noticed that there is a whining sound coming either from the engine or belt pulleys or bearings or transmission . . . and I would like some help from you guys. I'm not a mechanic, don't know to much about this engine and would like to ask before spending to much $$$ (ZAR).

From start, I notice a constant whining noise (almost like when you whistle, not a very high pitch, but goes up when revving or accelerating).
This sound does not go away after engine runs a few minutes.
However, when I use the clutch, I notice the the sound goes away (delay of about 1-1.5 seconds), almost like something is being detached or disabled. When I release the clutch the whining noise comes back again.

Ok, so I pressed the A/C button to see if there is any difference in the sound, and yes. The whining noise changes, but does not disappear. So it's something to do with the clutch and A/C!?

When I drive the BMW, in low revs and in First. The sound is very irritating and loud (this is with the Radio off, and yes it's the original fitted Radio, so it's not the sound of a bad power cable on the speakers or like that), going to second gear the sound is still there, third and forth it's softer but you still hear it. On high revs through Five and Six you can hear it, but it's a very high pitch you almost can't hear it. Almost like something is turning to fast and it's changing the noise/whining sound. It's destroying my driving experience!!!!!!

Please let me know what you guys think, I appreaciate the time you took reading this, and enjoy your BMW's like I do!

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      07-20-2016, 03:08 AM   #2
kkasson
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I don't have any experience with the N46 (I think that's what your car has?), but since nobody else has responded I'll give it a shot.

I recently fixed a whining noise on my N52. It was also related to the AC. I heard it mainly from idle up to about 1300 or 1400 RPM, at which point I couldn't really hear it anymore. If I was cruising and then slowed down and came to a stop, I'd hear it again as the tachometer dropped back down below about that point. It went away if I turned the AC off, and came back when the AC was on, but I didn't hear any difference at the compressor. The noise seemed to be coming from the vents, or inside the dash.

I also heard it more at night, which I later realized was because it would get louder and louder as the ambient temperature dropped. I couldn't hear it above about 75 degrees, and it got louder and louder below that point. My issue is that the AC system was just very slightly low on refrigerant. I added just a bit and the noise went away. I might not describe it as a whining sound...it was kind of more of a groaning.

The N52 (and I think N46, but I'm not completely sure) doesn't have a clutch on the AC compressor. It uses a variable displacement compressor which is spinning all the time. Turning on the AC just tells it to increase the compression. So a lot of the standard advice for clutched compressor doesn't apply here.

I don't know if that's the same issue you have, but I'd say it's likely to be from that or the belt, although I don't know why hitting the clutch would stop it. If it gets higher pitched the faster you rev the engine, I'd say it's more likely to be something with the belt. The belt is pretty easy to remove, you could try removing it and turning each of the pulleys. I believe people sometimes have problems with the alternator pulley.
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      07-20-2016, 04:02 AM   #3
AfteMath
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Thumbs up BMW n43b2000 engine

Well thank you kkasson for you input, and your time. Much appreciated.

I did some internet searches and came to the conclusion that it might be the Throw Out Bearing and the Clutch Kit.

Check this out, and then you will understand that it could be a worn bearing sound that spins to make the noise.



Pushing the clutch pedal in, will release the throw back bearing. Which releases the Clutch Plates, which disengage the throw out bearing. Releasing the Clutch will engage the Throw out bearing again to the Gear box shaft that spins creating the bearing to whine again.

Well it make sense doesn't it? hahah, if only you can think of it quicker lol. And without help, seems so logic. But hey, I didn't know this, but now I know.

I will get some quotes and post it, and I will ask my machanic if he thinks that this could be the problem as well. Will let you know.

Thank you for your post.
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