[bobc]

Hi,

E90 330i 2006, N52B30A


there is a strange noise coming from the engine bay - not sure exactly where is it coming from, if from the pulleys or the alternator? The noise is there no matter cold or warm engine.

I'm taking the car to mechanic for checking this issue next week. Any idea/experience what can cause this strange sound?

Attaching videos:

https://www.dropbox.com/s/ac7gnlgruk..._9519.MOV?dl=0
https://www.dropbox.com/s/n6wnf6ayib..._9518.MOV?dl=0

Is it safe to drive the car when it's making this sound or should I rather not?


Thanks for all the advices.

[Volasko]

Hmm thats a tricky one. Maybe the belt tensioner or maybe the belt. I assume the frequency of the noise changes with RPM?

[matteblue3er]

Maybe bad disa valve flapping around in the manifold

[bluewater328]

Originally Posted by matteblue3er

Maybe bad disa valve flapping around in the manifold

That usually only happens after 4k at speed (usually the large one too). I don't recall it ever happening at idle.

[matteblue3er]

Originally Posted by bluewater328

That usually only happens after 4k at speed (usually the large one too). I don't recall it ever happening at idle.

Yea well if the flap is broken, it won't matter what rpm you're at....

[Saico]

Originally Posted by matteblue3er

Yea well if the flap is broken, it won't matter what rpm you're at....

Confirm.

[bluewater328]

Originally Posted by Saico

Confirm.

Originally Posted by matteblue3er

Yea well if the flap is broken, it won't matter what rpm you're at....

Disagree. In theory yes. In practice, it'd be hard to hear. Ask me how I know.

[E92William]

Hey brother that's a weird noise. To me it seems synchronized with the engine speed which would lead me to believe is a weird pulley issue. To rule out a bearing you can have someone raise the rpm slightly and see if you can pin point where it's coming from, also you can try to see if turning on and off the AC changes it to pin point something with the compressor.

A trick I would use for squeaky pulleys and bad bearings in Autozone was get a can of pb blaster and or some other lubricant spray and with the engine running making that noise, you spray this at where the bearing of the pulley would be, one by one waiting in between a bit to see if any of them stops doing it.

Another thing you can do if this doesn't work and to rule out any belt issues is to remove the belt completely and turn on the engine. If it goes away then you can check every pulley by hand to see if there's any play or hard to rotate or who knows.

If not then given that you've got a 330i you can go and check the disas. If you don't got a nice scanner I recommend getting the bafx obd2 and getting an app like Carista or garagepro to deep scan the car to see if there's any disa codes. Either way the large disa valve is right on top of the throttle body in the intake manifold and you should be able to take it out and have a look at it. See the general condition of it if it's beat up then you can bet the small one is likely in similar shape and one of them flopping around could definitely cause a sound like this.

If you don't do your own oil changes take off the filter cap and look inside who knows if someone dropped something inside.. I've seen some weird shit. Try this and report back.

Implications of driving the car like this are varied. If a pulley lets go or seizes and the belt shreds it can wrap itself around the crank pulley and it can push the belt through the front main seal and into the oil pan and that's a 2000 dollar job to clean up.. found that out in my 335i
If it's a disa letting loose it can fall into your intake system and has a chance of destroying your engine so you definitely wanna fiddle with it this weekend if you can.

[hOlykamOtie*]

Similar sound to my old alternator, try playing with your AC and see if sound changes. I replaced my alternator with a recon and sound is gone. Good luck!