More idle issues after firing parts cannon to fix original idle issues

[80stech]

I don't know about that test but the drain for the CCV goes below the oil level so that it acts like a vacuum break for the cyclone, so yes, there should be bubbling if you force air down it.

I don't remember how hard it is to get to the vacuum hoses from the vacuum manifold to the CCV but if you can block/disconnect those (it might be a tee 2 into one) it might help to eliminate some things.

[Bdc101]

Originally Posted by 80stech

The diaphragm controls manifold vacuum to the crankcase and it's a "closed" system so any crankcase leak is also vacuum leak. If the diaphragm ruptures you get excessive vacuum "leaking" to the crankcase if you want to look at it that way.

The vacuum seemed about the same in the dipstick tube as in the crankcase. That would indicate that the diaphragm might have ruptured if your last sentence is true.

FWIW: I have not had any excessive oil consumption (though I really haven't driven it much this year) and I don't see any mayo very often except around the oil cap. No mayo visible in the vacuum lines that I can see.

Originally Posted by 80stech

I don't know about that test but the drain for the CCV goes below the oil level so that it acts like a vacuum break for the cyclone, so yes, there should be bubbling if you force air down it.

Ruptured diaphragm would cause both these symptoms then -- sounds like I'm taking the manifold and CCV off today then!! Thanks 80stech!

[80stech]

The dipstick tube is essentially part of the crankcase so vacuum should be same. By "vacuum break" I mean an extremely small difference to allow the tube to drain and create a slight resistance to pressure going back up.

A way to explain it backwards would be just enough pressure in the dipstick drain tube to force the oil down to just before a bubble happens

[80stech]

I would think that somebody (maybe on another forum) at some point must have measured how much vacuum there is in the crankcase when the CCV is working properly ??

[Happy]

Originally Posted by 80stech

I would think that somebody (maybe on another forum) at some point must have measured how much vacuum there is in the crankcase when the CCV is working properly ??

Edited: here’s 2 links that give the specifications,

https://static.nhtsa.gov/odi/tsbs/20...50094-9999.pdf

https://static.nhtsa.gov/odi/tsbs/20...45282-9999.pdf

It looks like the M54 measures in at 16.0 (mBar)


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ReVELaTiON 22:21

[80stech]

That's some good info!
16 millibar converts to about 0.5" mercury, much less than I would have thought!

As far the air bubbles in the oil, that also wouldn't happen if you have the special cold weather dipstick tube or if the tube has been drilled to make into one but chances of that are very very slim I would say

[Happy]

Originally Posted by 80stech

The diaphragm controls manifold vacuum to the crankcase and it's a "closed" system so any crankcase leak is also vacuum leak. If the diaphragm ruptures you get excessive vacuum "leaking" to the crankcase if you want to look at it that way.

Ok, so provided that the OP has corrected all of the air intake leaks. Essentially, wouldn’t the diaphragm be leaking metered air into the crankcase thus causing a rough idle or possibly even stalling?

I’m wondering if he got a defective ICV? I have personally gone through a few.


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ReVELaTiON 22:21

[80stech]

Any air (gases) coming from the crankcase going to the intake manifold is not metered. It could very well be a defective Idle Air Control.

[Bdc101]

I would agree except that I was getting the same code (idle air mechanical fault) with the old IAC valve (the original as far as I know) and the new VEMO replacement. Seems unlikely that a brand new one is failing in the same manner as the 22-year-old version.

Ok, so provided that the OP has corrected all of the air intake leaks. Essentially, wouldn’t the diaphragm be leaking metered air into the crankcase thus causing a rough idle or possibly even stalling?

I’m wondering if he got a defective ICV? I have personally gone through a few.

The crankcase doesn't ever pull air into it. Air that gets through the piston rings from combustion causes positive pressure. The point of the CCV is that it sucks that air into the intake manifold, but without exposing the crankcase to the full amount of intake manifold vacuum (which is quite strong vacuum downstream of the throttle body).


I'm still not 100% convinced it's the CCV, but I figure taking the whole darn intake off will be a good troubleshooting step. May just be a goofy broken vacuum fitting. It's either that or pay an indy out the nose to troubleshoot it for me. Since they aren't getting back to me and since the E70 is driving really great I think I'm just gonna park it in the garage for a few more weeks and take it all apart and maybe get lucky.

[Happy]

Originally Posted by Bdc101

I would agree except that I was getting the same code (idle air mechanical fault) with the old IAC valve (the original as far as I know) and the new VEMO replacement. Seems unlikely that a brand new one is failing in the same manner as the 22-year-old version.

You’d be surprised at the numerous times brand new parts arrived DOA over the many years of my automobile ownership. LoL..

Originally Posted by Bdc101

IThe crankcase doesn't ever pull air into it. Air that gets through the piston rings from combustion causes positive pressure. The point of the CCV is that it sucks that air into the intake manifold, but without exposing the crankcase to the full amount of intake manifold vacuum (which is quite strong vacuum downstream of the throttle body).

I’m not suggesting the crankcase pulls in air. I’m trying to convey that a failing CCV can over pressurize the crankcase.

Originally Posted by Bdc101

II'm still not 100% convinced it's the CCV, but I figure taking the whole darn intake off will be a good troubleshooting step. May just be a goofy broken vacuum fitting. It's either that or pay an indy out the nose to troubleshoot it for me. Since they aren't getting back to me and since the E70 is driving really great I think I'm just gonna park it in the garage for a few more weeks and take it all apart and maybe get lucky.

A smoke test would be most effective in finding a stubborn leak. But since you’re going to go through everything again, you may have a decent chance at solving the problem. Since vacuum seems to be the topic here, I’ve got a link that may help.

https://signalwires.com/bmw-m54-vacuum-diagram

I hope it all works out for you. I never like to see a fellow member in distress.


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ReVELaTiON 22:21