Strange Noise at High Speed - BMW Forum

SanDiegoBMW · 07-08-2011, 08:24 AM

This pertains to a 2008 528i.

Yesterday, while driving on the highway, I started hearing this strange deep whistling sound. It started occurring as I drove into an area where the outside temp was rising above 95 degF. It seemed to be caused by the air flow somewhere through the engine compartment. If I slowed down it went away. If I sped up, it came back. Once returning to outside temps below 90 degF, I could not reproduce the sounds.

Any ideas of what it might be?

Jack Dabsy · 07-09-2011, 06:37 AM

Is it happening at road speed or engine speed?

SanDiegoBMW · 07-09-2011, 10:33 AM

It is road speed dependent. Engine speed (RPMs) had no effect. While accelerating, coasting, or maintaining speed, the noise only got more intense or began to fade based on road speed.

To try to explain the type of sound....it's as if some of the engine compartment air seals or cowling (if there is any) were giving way when the outside temperature was high. My wife was in the car with me and we both thought the sound was coming from under the hood...possibly orignating more form the drivers side than the passenger (based on some crude triangulation).

The very next day I drove the same road at the same speed with the outside temps at 80 DegF vs 95+ DegF. No noise.

Jack Dabsy · 07-09-2011, 11:30 AM

Body vibrations... maybe the kidney grills or something similar !
Even the bottom engine cover...

SanDiegoBMW · 07-09-2011, 01:49 PM

Somone suggested the rubber in the front hood seals is contracting in the heat causing an air leak. What do you think?

Mr.West · 07-09-2011, 11:29 PM

As far as I know, things expand in heat and not contract!

Jack Dabsy · 07-10-2011, 10:40 AM

You talkin' about the corner rubber adjusters?
If yes then unscrew them Half a "Turn"...

SanDiegoBMW · 07-10-2011, 10:52 AM

Quote:

Originally Posted by Dabsy

You talkin' about the corner rubber adjusters?
If yes then unscrew them Half a "Turn"...

Thanks. I'l try that.

Jack Dabsy · 07-10-2011, 11:13 AM

Quote:

Originally Posted by SanDiegoBMW

Thanks. I'l try that.

Unscrew afurther half turn if the vibration/whistle persists....
This may make your hood "Lift" at one corner... If it does then raise the opposite side or lower the "raised" side... You will find the right setting eventually... Good Luck mate

SanDiegoBMW · 07-10-2011, 08:45 PM

Outside temps have cooled off. As is...there is no noise at temps <90 DegF. I'll have to try the adjustments during the next heat wave. Again thanks!

DaGunster · 07-12-2011, 12:46 AM

Head out to Anza Borrego - you have a great test-bed clear to November it'll be over 90 out there.

SanDiegoBMW · 07-12-2011, 07:43 AM

Good idea.

Penngwyne · 07-20-2011, 10:00 AM

I had a strange and loud noise at speed above 90 kph, sounded like a buzz in the area of the speedo but turned out to be lack of fasteners on the plastic grill over the plenum chamber. Temp fixed with duct tape.then finally got new fasteners and no more noise.

Of course headwinds or tailwinds will affect this particular noise (airspeed) and the indicated speed it will occur at may vary.

SanDiegoBMW · 07-22-2011, 05:48 PM

I'd like to check this out, however I am hindered by ignorance....where is the plenum chamber?

Penngwyne · 07-24-2011, 06:46 AM

Quote:

Originally Posted by SanDiegoBMW

I'd like to check this out, however I am hindered by ignorance....where is the plenum chamber?

The big hole under the plastic grill around the wipers, where the air goes into the car through the heater/aircon. (at least that's what I thought it was called)