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There should only be 3-6 water inches of vacuum in the crankcase when the engine is idling. Best place to measure it is at the dipstick tube. If there is agressive vacuum there, the crankcase vent valve is bad.
 

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Discussion Starter · #4 ·
I notice that there is quite a strong suction at the slit on the side of it and if I block it off the car dies, I have noted that others here have said there engine gets smoother when they block it off. Just trying to remedy the rough idle problem that I have.
 

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The normal pattern of flow is from the Valve Cover into the CCV, then heavier oil is channeled into the small hose that goes to the dipstick, and vapor (combustion by-products) goes back to the Intake Manifold:



I don't know how many miles you have but if you have rough idle, then it is better to do this whole DIY (see link below):
http://www.bimmerfest.com/forums/showthread.php?t=379225&highlight=ccv+cn90


Basically shooting 5 birds with one stone!

1- Replacing Oil Line to Vanos (mine is leaking).
2- Replacing CCV and hoses (preventive).
3- Cleaning ICV and replace its hoses (preventive).
4- Cleaning Alternator Air Duct and Installed Gutter Guard to prevent leaves from being sucked in.
5. All Intake Seals/Gasket
 

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Discussion Starter · #11 ·
I notice that when I start the car with the pipe to the icv disconnected from the airbox that the car idles ok I have also plugged the hole in the airbox that the pipe was in - does this indicate anything further?
 

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I can feel quite large sucking suction when I lift the oil cap and/or dipstick. I have non vanos M62. Idle even changes when I lift the oil cap. I've replace the intake cover in the back, but no change. Can anyone tell me what's wrong?
 

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Discussion Starter · #13 · (Edited)
Just to update I have removed the CCV and cleaned it and to be fair it wasn't that dirty - confirming that the previous owner had replaced it, the pipe to the vanos was also replaced (it even still had the label on it and dated 4 months ago) but I give it a good inspection anyway and it was fine. The pipe to the dipstick tube on the other hand was very spongy and completely blocked so I replaced it and I also replaced the dipstick tubes O ring as a preventative measure. I had replaced the ICV and inspected its pipe before and have also replaced the air flow meter as well. Dipstick and oil cap seals are good and all seals around the airbox and throttle body checked as well.
As I said earlier, I notice that when I start the car with the pipe to the ICV disconnected from the airbox that the car idles ok, I have also plugged the hole in the airbox that the pipe was in when doing this - does this give anyone an idea of what the problem could be.
Any suggestions as to what else I could check/do.

Thanks so far for all your help m8's.
 
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