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Old 02-17-2012, 06:42 AM
cn90 cn90 is offline
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Location: Omaha NE
 
Join Date: Mar 2006
Posts: 12,835
Mein Auto: 1998 528i 5-sp 140K+
Good job.

For the purpose of my post, I use the words PCV and CCV interchangeably.

I used to own an E23 (1983 735i 5sp), the PCV in that car is very simple, it is just a hose from the valve cover going to the intake.

With the E23 PCV system, crankcase vapor (which is mostly blow-by combustion product) + a tiny amount of oil re-enters the Intake Manifold.
IIRC, my E23 drank 1L engine oil for every 5000 miles, so it was not so bad.
Every so often when I opened the E23 Intake Manifold, there is a tiny amount of engine oil in there, maybe a drop or 2, no big deal.

Since then, BMW changed the design, in the E39, the idea is the same except now the CCV device has a vacuum diaphragm. At certain pressure, the diaphragm opens allowing blow-by combustion product to re-enters the Intake Manifold, while keeping the oil back so the oil is not allowed to enter the I.M.

Nice idea until the CCV fails, now tons of oil enters the I.M., thus blue smoke in exhaust.

If you compare a brand new E23 PCV vs a brand new E39 CCV system, I am not convinced that the E39 consumes less oil to start with.


Here you go, it is #11 in the picture below (from my 1983 735i), this will give you an idea how it used to be.
Notice that in the E23, the PCV pipe slopes UPWARD (because the Intake Manifold sits high), so any oil naturally flows DOWNWARD.
(In the E39, the I.M. sits BELOW the Valve Cover for aerodynamic reasons, thus the convoluted CCV design in the E39).


Last edited by cn90; 02-17-2012 at 06:46 AM.
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