[truajb]

Dear members, I hope someone can help to identify the issue I am having. I am hearing a wheezing or "woooing" noise only when the vehicle is at around 750-1250rpm, both accelerating and decelerating. Over 1250rpm the noise just disappear (I think it's masked by the regular engine sound). It's more noticeable especially when the vehicle is decelerating as the engine quiets down. I have changed numerous parts hoping to fix the problem with no success. Below are what I have replaced,

- Lower and upper intake boot
- Tensioner pulley
- Idler pulley
- Alternator pulley
- AC belt
- Serpentine belt
- alternator
- water pump
- replaced spark plugs and air filter
- DISA removed and inspect and found working properly

This problem was first noticed about 3 months ago after my mechanic topped up the freon. I switched both the A/C and air circulation off and the noise still can be heard. It tells me it's not the AC. The AC makes it a little louder at times but it's not the root cause.

I brought the vehicle to a couple reputable local Bimmer shops and the mechanics told me the noise comes from when the alternator recharges and it's normal. I am not convinced because I have driven other 325xi without the noise. Also, if the noise is normal I wouldn't think anyone would have bought a bimmer to begin with. It's not super loud but without turning the radio or music on you can definitely hear it.

I seem to have done everything people suggested from different forums but the root cause is still not identified Please, I love my bimmer and I hope some knowledgeable folks can help.

 

[LRod]

One thing that might help us more is where the sound it coming from. Does it happen if you rev while stationary? What about moving? It could be a bearing, an exhaust leak etc etc etc. You did a lot to the car, but must probably wouldn't cause that type of noise. What about WOT, what happens then? Power decrease, bad smelling exhaust, etc??

 

[truajb]

Mine is an auto with about 130k km on it. Seem to be losing a little torque on low end but not significantly. The noise seems to come from behind the center vent. You can only hear it when the windows are up. I tried to rev the car on idle and it can still be heard but not as loud as when the car is running. To me the noise sounds like an air or vacuum leak but I assume I would see a code if it's vacuum leak.... What kind of noise would be associated with RPM?