Whistle/whine/squeal at WOT?

Hey guys,

Just came back from my first roadtrip in my BMW (OH to NJ and back again). Man this car is smooooth!

This meant that I finally had some solid opportunities to see how my car behaves at WOT while shifting through the gears. I noticed that if I was at WOT, around 4500 RPM a whistle/squeal/whine (hard to describe unfortunately) would briefly appear. It would get louder as I neared redline. If I shifted near redline, the whistle would fade out and resume, again increasing as the RPMs surged higher. Only when I hit 6th gear (and presumably left the powerband) the whistle would drop out entirely even if I went WOT, like when flooring it in 6th to go from 75 to 80.

I recently changed my oil and belts (but not pulleys) before going on the trip, so I wonder if my underdrive pulleys are just starting to go, and its only noticeable at high RPM? Normally, I don't take the car much beyond 3,000 in my daily drives, so I could see this. Does this sound likely to you guys?

Thanks, I would also appreciate any other ideas I could look into.

Either intake boot crack or water pump going bad I had the same problem but it was the water pump.

Originally Posted by I8URAMG

Either intake boot crack or water pump going bad I had the same problem but it was the water pump.

Thanks for the reply, I8URAMG!

Uh oh, I'm hoping not the water pump I know that the thermostat and possibly the expansion tank were overhauled by the PO, but the waterpump looks original... Is there anything else I can do to help pinpoint the water pump as the cause??

Really not much its hard to pinpoint what year and model is it?

Pop the hood, and have some rev the car for you, while you listen for the noise and see where its coming from

vacuum leak. check the intake boot and the little piece that comes off it to the idle air valve. i circled the pieces

It's the deer whistles on your bumper. I bet you didn't hit any deer during your road trip, did ya!

Just your supercharger.

I got today a high pitch whistle noise , but bearably could be heard, but could be heard at idle. So I did troubleshooting, with air conditioner and without. So I shut down a car for second or two, start up again without air conditioner, so there is no whistle noise can be hear, then turn on air conditioner and whistle come back after 1-2 min working at idle speed. I have tried increase RPM, but a whistle have not increased. So I went to read here and bimmerfest about the whistle, after 30-40 min, I have start up a car again without air conditioner and drove for couple miles, the whistle didn't come back and same happened with air conditioner after couple miles. I have checked a famous duct/boot, there is no holes I couldn't find while visual inspection. There is no check engine light.
Any ideas?

i have the same whistle - and i have no idea what it is. i already checked the intake boot for leaks, its not that. im guessing its prob the water pump.

I have more of a mechanical sounding whine at WOT. I thought it was the lower intake boot, but I replaced it and it still making the sound. I've been reading up here on CCV and the DISA causing problems, mine has developed a bit of a rough idle. I have new belts and pulleys, and haven't had any coolant related issues

Originally Posted by BMW_Stu

vacuum leak. check the intake boot and the little piece that comes off it to the idle air valve. i circled the pieces

Thanks, I will definitely check that out!

Originally Posted by Hrvat

Pop the hood, and have some rev the car for you, while you listen for the noise and see where its coming from

Why didn't I think of that... Thanks!

I have low pitched noise..(Something rotating? hard to explain...). something similar to noise that you hear when a/c is on..
but it gets louder if rpm goes up..
It is loud and comes and goes... it's there about 70% of time tho..

Any idea where this noise is coming from?

i thought all of our cars whistled?

You actually have to take this out to see this. The best DIY I have done so far, the whistle noise was driving me Insane Make sure you have the right boot before taking it all off. Stealership gave me a wrong boot, very similar to the one that was torn but I made it work anyway, just looks kinda wierd There is a step by step with picture somewhere in the forum, just search for it.