Pulsating Air Noise coming from engine
 

2000 BMW 528i e39.

I have a noise that sounds like air passing over or through some kind of diaphragm. It sounds like it is coming from the driver's side of the engine near the center of the block under the air ducts. There is a part mounted to the engine with smaller hoses attached which I don't know what its for but the sound seems to be coming from the area.

It is especially loud when the engine is cold. When warmed up, it is louder when accelerating. It is not a steady sound, it's more of a pulsating noise.

The engine seems to run fine although at times it idles rough cold.

Any ideas?

There is an air/oil separator near that location but closer to the front of the engine. It is connected to the crankcase vent near the front of the valve cover and the intake manifold and the base of the dipstick tube. The purpose is to vent crankcase vapors back to the intake manifold for polution control. It is supposed to separate the oil contained in the vapor and return it to the sump through the dipstick tube. These devices are known to fail on the 2.8 liter engines in the 328i and 528i models. That would be the first thing I suspect from the symptoms you describe.

After doing additional internet research, isn't this related to the CCV system? I was planning on replacing the CCV and all related hoses. Is what you've mentioned one of the hoses attached on the other end to the CCV?