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-   -   Whistling sound upon cold start up (http://www.m3forum.net/m3forum/showthread.php?t=337742)

M302_IMOLA Fri, Oct-08-2010 06:12:41 PM

Whistling sound upon cold start up
 
The past few mornings I have been hearing a faint whistling sound when I first start my car up (have to mute the radio to hear). The sound seems to last about 3-5 minutes and then disappears as the car warms up. The best way to describe the sound is it sounds like a very faint table saw...you know that high pitch sound you hear when you start up a table saw. The sound seems to get a little louder as the accelerator is pressed. Anybody else ever heard this before on their M? I can't help to be paranoid and think bad thoughts (i.e. vanos, cam gear bolts).

PenguinQX Fri, Oct-08-2010 07:42:22 PM

Yes, but on my car it's the supercharger :)

In all seriousness though, I never encountered this before when I was NA. Ever pop the hood to figure out where exactly it's coming from? Belts maybe? Bad belts can be noisey on startup and go silent after the engine warms up.

ShafferMD Fri, Oct-08-2010 08:08:27 PM

Air Leak
 
I would lean closer to a possible idle air intake or vacuum leak. Check around, it is likely that you have a crack or split in one of your lines. A small leak will not generate a code as the computer is able to correct the lean condition (if it is pre-MAF) or your not out of range yet on your O2 sensor readings (post-MAF). Our cars are getting older and the constant heat cycling of the engine compartment causes premature failure on the rubber connections in the air circuit.

My daughter's car ('03 325i) had the same condition but eventually threw a code for Bank1 / Bank2 lean.

Can be difficult to find, but easy to fix...

- Good Luck -

E-solo Fri, Oct-08-2010 09:45:40 PM

Im so glad you brought this up. I have 2 years experience with this whistling deal and I gave up on it. Here is some background on my experience with this:

Started with a faint whistle, which became more noticeable with time. It seemed to be louder when the weather was cold. Then it started happening while I was driving, so it sounded like canaries under my hood. It went away a bit during the summer, when the weather was warm. It comes back each winter when it gets cold out. Just started this week, as here in California is got a bit chilly.

I have taken the car to the dealer various time for this and had to show the dealer how to recreate the sound. They took apart my SMG and put it back together because the extended warranty would not pay for a repair. I decided to just leave it alone. The whistling went away for a while and comes back periodically. Not the dealer, not any indy shop has been able to tell me the problem.

BTW, I thought it was the SMG, but later realized it wasn't. Its obviously something else because my SMG is fine.

chris9 Fri, Oct-08-2010 09:49:28 PM

I had a similar sound that was prominent at start up but would go away as the car warmed up. Turned out to be the alternator, you may look into that.

MPOWERD Fri, Oct-08-2010 10:55:35 PM

I have heard this as well, comes and goes. My shop could not track it down either...

M302_IMOLA Sat, Oct-09-2010 03:25:05 PM

Quote:

Originally Posted by PenguinQX (Post 4982517)
Yes, but on my car it's the supercharger :)

In all seriousness though, I never encountered this before when I was NA. Ever pop the hood to figure out where exactly it's coming from? Belts maybe? Bad belts can be noisey on startup and go silent after the engine warms up.

Lol, I figured I would get some snide remarks regarding a supercharger. Good points on the belts, I will have to check them out.

Quote:

Originally Posted by ShafferMD (Post 4982578)
I would lean closer to a possible idle air intake or vacuum leak. Check around, it is likely that you have a crack or split in one of your lines. A small leak will not generate a code as the computer is able to correct the lean condition (if it is pre-MAF) or your not out of range yet on your O2 sensor readings (post-MAF). Our cars are getting older and the constant heat cycling of the engine compartment causes premature failure on the rubber connections in the air circuit.

My daughter's car ('03 325i) had the same condition but eventually threw a code for Bank1 / Bank2 lean.

Can be difficult to find, but easy to fix...

- Good Luck -

I did recently install a streamline panel air filter and Afe elbow...I have checked them out for leaks but didn't see any.

Quote:

Originally Posted by E-solo (Post 4982767)
Im so glad you brought this up. I have 2 years experience with this whistling deal and I gave up on it. Here is some background on my experience with this:

Started with a faint whistle, which became more noticeable with time. It seemed to be louder when the weather was cold. Then it started happening while I was driving, so it sounded like canaries under my hood. It went away a bit during the summer, when the weather was warm. It comes back each winter when it gets cold out. Just started this week, as here in California is got a bit chilly.

I have taken the car to the dealer various time for this and had to show the dealer how to recreate the sound. They took apart my SMG and put it back together because the extended warranty would not pay for a repair. I decided to just leave it alone. The whistling went away for a while and comes back periodically. Not the dealer, not any indy shop has been able to tell me the problem.

BTW, I thought it was the SMG, but later realized it wasn't. Its obviously something else because my SMG is fine.

Good info, thanks for sharing. It has been getting colder down south now which confirms your thoughts on it being louder during cooler weather. I swear the sound doesn't sound normal though...I have been loosing sleep over it.

Quote:

Originally Posted by chris9 (Post 4982778)
I had a similar sound that was prominent at start up but would go away as the car warmed up. Turned out to be the alternator, you may look into that.

Could be...my car has a little over 105K miles and is on the original alternator as far as I know. At what mileage did yours go out?

Quote:

Originally Posted by M3_Modness (Post 4982894)
I have heard this as well, comes and goes. My shop could not track it down either...

Since you're in Texas and it has been getting cooler, have you been hearing it more lately?

FLBMWM3 Sat, Oct-09-2010 03:47:29 PM

I would lean towards the alternator or possibly the tensioners.

E46er4Life Sat, Oct-09-2010 04:12:31 PM

To me it sounds like it may be secondary air pump. Maybe a vid would help.

chris9 Sat, Oct-09-2010 11:30:05 PM

Quote:

Originally Posted by M302_IMOLA (Post 4983577)
Could be...my car has a little over 105K miles and is on the original alternator as far as I know. At what mileage did yours go out?

Car is a 2004, alternator went out at 95,000 miles, red battery light came on.
We were seeing 100+ outside temperatures which I believe expedited the failure.
Car is garaged and majority of miles were highway.


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