ukr

Started car in the morning and noticed idle fluctuation. Drove about half hour and started hearing whistling noise between from idle to 2k rpm, almost like belt slipping except it didn't get louder with rpm increase. When I arrived at work put trans into park idle was above 1k rpm while I could hear whistling. Belt and pulley were changed not long ago. n52 with 144k miles. Any ideas what it could be?

donpb

That sounds like a vacuum leak to me.

scottalexander

The whistling problem is typically and characteristic of a broken rubber diaphragm membrane in the PCV system (which is embedded in the valve cover near cylinder 6).

You can see this on Youtube. Its about the size of a tennis ball.

There are some guys that try to replace the rubber diaphragm in the valve cover and glue it back together. That's like putting toothpaste back in the tube.

If the problem is the PCV in the valve cover, you have to buy a new valve cover.

I just replaced my valve cover a few months ago at 53,000 miles due to it leaking oil. However, now that it has a new PCV in the valve
cover it idles perfect and is very smooth. I was working at a fast pace and it still took me 5 hours.

gman6262

Here's the link for the membrane replacement kit: https://vanos-bmw.com/product/111275...53-11127548196 This page also gives a simple troubleshooting guide. If it's broken, you can't break it any more and maybe you save the cost of a new valve cover.

scottalexander

Its nice saving $450 and replacing the membrane for only $20.

But here's the thing...

I looked at the pictures in the link. Replacing the membrane is art work or a hatchet job.

If you are going to spend hours removing the valve cover and reinstalling it, only to find out you needed to replace the valve cover gasket, or the valve cover was weak and cracked, etc, etc, then you might as well bite the bullet and get a new valve cover for all the work you will need to do anyway.

What I realized is at some point everyone who owns a N52 knows you will be replacing the valve cover (whether you like it or not).

ukr

Thanks everyone for your responses! The noise hasn't happened since. If the CCV diaphragm is broken wouldn't the noise be there always or is it intermittent? It sounded like this vid I also ran a scan for computer codes and got a "002A82 Inlet Vanos", never had this code before and I regularly check. 2006 n52 has the CCV attached to the intake manifold instead of the valve cover.

After doing some research on Vanos code found out it could be caused by Camshaft bearing ledge wear. https://static.nhtsa.gov/odi/tsbs/20...32779-2821.pdf
I will test for Vanos first by swapping intake with exhaust.

scottalexander

Now that I know you have a 2006 model with the PCV attached to the intake manifold, its a different ball game for you than I described above.

Next:

Every whistling noise I've witness is constant once it starts, but can get louder and softer with load.

I see in the video they have a difficult time getting off the oil cap. When my membrane broken inside my valve cover I experienced the oil cap problem.

When I replaced my valve cover I also replaced the oil cap (the gasket deteriorates over time).

ukr

The video isn't my car, but it sounded almost like that. I haven't heard this noise since. Did yours consistently made the noise while running?
I also noticed very slow engine cranking, possibly failing starter motor because the battery was replaced few years back. Bizarre all these problems are coming at once.