very high pitch squeal under light accelartion

[tazzer]

Hello, got a 2003 X5 3.0i auto
Have noticed when under light acceleration, for example lightly press acceleration from standstill (1cm on gas pedal) it causes an extremely high pitch noise from somewhere under the car, seems to left side as is louder when left window is wound down.
(If you have ever heard one of those high pitch dog whistles, it sounds exactly like one of those whistles.)

It only appears when accelerating lightly, so if you put your foot down or are stationary or even revving when stationary you cannot hear the high pitch sound.

Anyone got any glue what it could be? Was wondering if it might be waterpump or belts / tensioner???

[Bianca98]

could be a bad idler pulley, could just be the belts, could be there is a small vacuum leak in your intake/intake piping. Could be wheel bearing, could be brakes. Better test would be to have someone else sit in the car while you get out and start poking your head in places to see where the noise is coming from.

[beamertruck]

Honestly from what your describing, its probably a wheel bearing

[tazzer]

Originally Posted by beamertruck

Honestly from what your describing, its probably a wheel bearing

Hi no def not a wheel bearing as the sound disappears when you back off accelerator or floor it. Thanks for the suggestion though

[tazzer]

Originally Posted by Bianca98

could be a bad idler pulley, could just be the belts, could be there is a small vacuum leak in your intake/intake piping. Could be wheel bearing, could be brakes. Better test would be to have someone else sit in the car while you get out and start poking your head in places to see where the noise is coming from.

Thank You, good suggestions, the vacuum leak sounds like it could be worth investigating as the sound is only there with slight acceleration only. It doesn't do it when reving stationary at all so is going to be difficult to diagnose as you can only hear it when driving and when left window is down.

[BigBlack48is]

I have a very similar sound under light acceleration and only when it's cold ( sitting all day or night ). I am pretty sure my mystery sound is something in the transmission. And the reason I am assuming this is because I have already changed the filter/fluid and it didn't change. And I have herd a very similar sound from another bmw next to me at a light....

[bcredliner]

Some things you could try to narrow it down:

Try holding the engine at increasing RPMs, from idle, in park, to see if you can hear the sound. Then, in drive, with the brakes on, increase the RPMs from idle 250 at a time and hold them steady for a short time, to see if you can hear the sound. If you hear no sound from either it is far more likely the sound is associated with something that only moves when your X is moving and we can go from there.

[beamertruck]

could be thr CCV, mine used to squeel like that.

[mrbmwx5]

Your x5 came with supercharge system .... Lol
Crack elbow intake boot... Check it out.

[Peregrin-O]

Cracked elbow intake boot