X5M High Pitch Whistle When Boost Kicks In

[SnowsM3]

I have a 2011 X5M and when the turbos kick in there is a very brief, very high pitch whistle which lasts for a brief second then comes back for the same brief second when I lift or shift gears. If I keep the throttle planted the whistle still only lasts for a brief second then goes away until I get off the throttle. The whistle doesn't keep going while the turbos are working either....only when they first kick in or when I lift or shift. Doesn't matter what speed or what gear. Doesn't matter if it's full or partial throttle. The key is getting the turbos to kick in. It's pretty loud too because anyone can easily hear it over the wind noise at 50mph.

My guess is that it would be some sort of "wastegate" or "blowoff" valve but I thought those only activated during lift throttle/shifting. I also don't think it's the turbo unit because the sound only lasts for the first brief second even while the car is still accelerating then appears again for a brief second when I lift.

Anyone experience the same thing? Any input is greatly appreciated. Thanks.

[JupiterBMW]

If it's as loud as you say, perhaps a sound clip?? Would help diagnose it for sure.

[SnowsM3]

After driving it some more last night the sound has gotten a little worse. It's a little louder and it is longer in duration. I took the Head Tech for a test drive and he agrees that the car shouldn't be making that noise. He thinks it's an air filter or intake leak of some kind since I just had the car in for it's 30,000 mile service and they replaced the air filters. He gave me the car back because he doesn't believe it's anything but an annoyance sound. I'll be out of town for the weekend so I'll bring it back on Monday or Tuesday and they're going to replace the air filters again, replace the intake hoses, & make sure the intake seals are good. I'll keep you updated as I know more.

EDIT: I won't have time before I leave but I'll try and record a quick video of the sound when I get back.

[Centrofly]

had the same issue a few months back. its not normal. you have a small cracked hose that connects to the intake, cheap plastic hose wears down from engine heat. Should take them an hour to fix it. sounds like a high pitch whistle. I had them replace both intake hoses.

[SnowsM3]

Thanks for the info. I'm bringing the car back to the dealership tomorrow morning. What you described makes sense. Hopefully I'll close out this thread with the solution tomorrow.

[toptounov]

Originally Posted by SnowsM3

I have a 2011 X5M and when the turbos kick in there is a very brief, very high pitch whistle which lasts for a brief second then comes back for the same brief second when I lift or shift gears. If I keep the throttle planted the whistle still only lasts for a brief second then goes away until I get off the throttle. The whistle doesn't keep going while the turbos are working either....only when they first kick in or when I lift or shift. Doesn't matter what speed or what gear. Doesn't matter if it's full or partial throttle. The key is getting the turbos to kick in. It's pretty loud too because anyone can easily hear it over the wind noise at 50mph.

My guess is that it would be some sort of "wastegate" or "blowoff" valve but I thought those only activated during lift throttle/shifting. I also don't think it's the turbo unit because the sound only lasts for the first brief second even while the car is still accelerating then appears again for a brief second when I lift.

Anyone experience the same thing? Any input is greatly appreciated. Thanks.

Try crank shaft breather hose, around $60 in Canada. Tends to crack over time and temperature, it's made out of plastic. And when it's brakes it sound like a whistle, as air gets sucked in at high pressure.

[SnowsM3]

The problem has been fixed. No more high pitch whistling when the turbos kick in. Here is the description of what they replaced with part #'s:

"Smoke tested intake system for both banks found intake leak at fresh air duct to turbo seals. Found engine oil sweating from crank case vent pipes, which are combined with fresh air ducts on this motor. Replaced both crank case vent pipe assys with new seals. Reassembled engine completely and rechecked for noise. Found noise improved but still present on drivers side. Smoke tested intake again and found connecting line for left side leaking. Replaced connecting line for left side. Reassembled vehicle and rechecked. Noise no longer occurring."

13-71-7-848-151 Filtered Air Duct
13-71-7-848-152 Filtered Air Duct

They also replaced one of the crank case vent pipes because it was sweating oil. These are the crinkled pipes that go over the turbos. Someone posted a picture of it in another thread. I couldn't get them to replace both under warranty. I'm going to have to wait for the other to start leaking I guess.

11-15-7-589-992 Vent Pipe

Link to picture of vent pipe that goes over the turbo.

http://www.xbimmers.com/forums/showthread.php?t=954887

I hope this helps someone in the future. Good luck.