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Old 02-28-2016, 02:58 AM   #1
jessem
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Constant Whistle Noise



I recently bought a 2011 135i which has the N55 engine and dual-clutch transmission. There is a very audible whistle noise between 1000 and 2000 RPM. It is a constant sound, unrelated to what the car is actually doing at the time. In other words, doesn’t matter if it’s accelerating, decelerating, or just cruising… the whistle is there. Couple other things… The higher the RPM (between 1000 and 2000), the higher the PITCH of the whistle. I’m certain of this. So the pitch of the whistle in unrelated to the speed of the car. It’s directly related to the speed of the engine. Also, the noise seems to only be audible when the engine is warm. Any ideas? Thanks!!
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Old 02-29-2016, 01:29 PM   #2
nikijack
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Maybe a stupid response, but, could it be coming from the radio?
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Old 02-29-2016, 08:04 PM   #3
jessem
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Thanks for your response. Definitely not anything from the audio system.
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Old 03-05-2016, 02:20 PM   #4
cheapthrills
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I don't know if the E82 has the same setup, but the E46 has a vacuum line running underneath the dash to operate the MPG gauge. This line can rub against the steering column and leak, which can make it whistle. However, this whistle would usually change with vacuum changes (on/off throttle for instance).

Below is the DIY for the E46:
http://forum.e46fanatics.com/showthread.php?t=533035
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Old 03-05-2016, 02:38 PM   #5
jessem
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Forgive me.. I know very little about cars. Are you referring to a vacuum leak? If so, this has been ruled out by multiple mechanics.

A new mechanic suggested that maybe the previous owner used a less than ideal engine oil. He said changing the oil to LIQUI MOLY with the BMW Longlife 01 rating and new filter might solve it.
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Old 03-05-2016, 03:27 PM   #6
Blackedout95
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A whistle due to oil?

Highly unlikely!

What it could actually be and keep in mind I am guessing

You are hearing the turbo spool
You have intake piping issue (leak off)
I think there are 2 hoses that run to the intake on the drivers side, check them
Sure its not the fuel pump whine?
Does it only happen under boost?

Worst case a hose, pipe, fuel pump or even turbo!

Again just a guess or 2
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Old 03-05-2016, 04:37 PM   #7
jessem
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I think he meant maybe the filter? Guess I'll find out soon from an oil change.

And I will mention to the mechanic your suggestion to check those hoses.

I don't know what the fuel pump is, nor what a fuel pump whine would sound like.

The sound is there in all circumstances.

Thank you!!
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Old 03-06-2016, 12:21 AM   #8
Blackedout95
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Have him check those two hoses and the intake pipe, all associated turbo hoses for leaks, loose clams etc. The fuel pump if loud he should notice as well as if the turbo spool is noisy under load and changes when quickly off.

All the best!
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Old 03-06-2016, 05:23 PM   #9
jessem
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Got it!

I should have mentioned, more than one BMW mechanic has told me that they've heard this exact noise in some naturally aspirated BMWs, so they believe it's unrelated to the turbo. Of course, I can't be certain the noise truly was the same.
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Old 03-06-2016, 09:44 PM   #10
Blackedout95
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I hear ya, just need to narrow it down which hard to due over the web Mind you never heard a whistle from a filter, if truly a whistle.

I also know many things can cause many variations of whistles as well in nat and turbo cars as having heard many different noises from the oil filter housing for varying degrees.

I am just guessing and connecting dots, shifting, low end whistle noise..turbo car pipes and hoses and turbos oh my! Just a first thought thing. AT least we can rule out BOV.

Id say if you hear a very distinct whistle always in that situation cant hurt to go over the turbo system
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Old 03-06-2016, 10:35 PM   #11
jessem
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Will do. Thanks - I appreciate everything!
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Old 03-07-2016, 05:44 PM   #12
MANDD
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There are some issues with the front and rear crankshaft seals on the N55 motor (small production range). The fault is the tolerance of the lip on the seal. When you take it in for service have them raise the car and listen for the noise near the bell housing.

If the noise is found to be in this area lower the car, while listening to the whistle noise slowly loosen the oil cap to relive crankcase pressure.

If the noise starts to diminish then the rear crank seal will require replacement.

For the front crank seal I have only seen this whistle when depressing the brake while driving then the noise will start. In this case stop and loosen the oil cap if the noise diminishes then the front crank seal will require replacement.

Mark.
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Old 03-07-2016, 08:01 PM   #13
jessem
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Awesome. I'll pass this along to the mechanic. Thanks Mark.
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Old 03-09-2016, 12:17 AM   #14
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Is the whistle present only when driving? Or does it make the noise while stopped too?
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Old 03-09-2016, 05:50 PM   #15
jessem
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Good question! I just revved the engine in park and yes, the noise is there. Again, it seems pretty limited to the 1000-2000 RPM range.

Thanks.
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