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Discussion Starter · #1 ·
I just came across this interesting little trick for diagnosing blocked CCV in the Volvo forum:

With the oil cap sealed, engine on, stick a balloon over the dipstick tube and see if it inflates. If it inflates you need to service the PCV system.

...Lee


I think he meant with the dipstick removed, so the balloon goes over the dipstick housing.

No balloon, no problem, get an old dish washing glove, cut a "finger" off and tie it with rubber band.

http://www.matthewsvolvosite.com/forums/viewtopic.php?f=1&t=28322
 

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Discussion Starter · #5 ·
..if the ballon trys to be sucked into the
dipstick hole just a little that all is OK--if it's being sucked in at a high rate though the ccv could be going bad.
Poolman,

Dipstick housing represents crankcase prssure, so it is almost always high from blow-by combustion. The dipstick can never suck in.

Vacuum exist in the Intake Manifold only.
 

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Discussion Starter · #7 ·
In a nutshell, the crankcase always produces pressure from blow-by. The CCV is simply a "middleman" controlled by Intake Manifold Vacuum.
This way the positive pressure from the crankcase is removed by the CCV which separates oil and vapor:
- Oil goes back down the crankcase
- Vapor goes back into the Intake manifold.

This is why the CCV is also called "Oil Separator" in the Volvo language.
 

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Discussion Starter · #10 ·
Fudman,

The best way to look at this is:

1. "A" is the crank case pressure. It is the same whether you measure it at the Top Valve Cover Outlet or the Dipstick because the Top part of the Engine Cam Lobes area connect to the sump via some air channels (this is how crankcase air goes from the sump upward into the cam lobes area).

2. "B" is the Intake Manifold Vacuum.

The following numbers are arbitrary just to illustrate the concept.
Sea level air pressure is 760 mm Hg or 14.7 psi. But let's set this as zero as a point of reference purpose.

And let's say the CCV is designed such that when there is a differential of 3, it opens the spring allowing vapor to return to the I.M.

Scenario A: car warm and idling at 700 rpm:
- Atmospheric air "zero"
- Intake Manifold vacuum = "- 1"
- Crankcase Pressure: goes slowly from "1" to "3" (from blow-by)

At "-1" and "1", the difference is only 2, so the CCV is closed, but at -1 and 3, the difference is 4 so the CCV is open allowing vapor to return to the I.M. At the same time, liquid (oil) is allowed to flow back down the crankcase drop by drop (basically dripping, not a full flow).

Scenario B: you are driving at 3000 rpm:
- Atmospheric air "zero"
- Intake Manifold vacuum = "- 3"
- Crankcase Pressure: goes slowly from "3" to "5" (from blow-by)

In this case the CCV is always open because the min difference is still 6.



Maybe one of us can get a birthday balloon and play with it this weekend and report back (assuming your CCV is fine)?
 

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Discussion Starter · #69 ·
Wrong... Pull your dipstick with the engine running. There is vacuum. Pressure would cause the dipstick to shoot out.

Sent from my LG-G6 using Tapatalk
In the world of Physics, a pressure in a chamber can be positive or negative. When it is negative (against ambient atm), it is referred to as "vacuum".

So the word pressure is a generic word in the Physics world.

Normal: slight vacuum.
Blocked CCV: pressure builds up and can blow the dipstick or RMS.

This is why I posted that sentence in this thread, which talks about blocked CCV.
 

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Discussion Starter · #78 ·
Well,

When a PCV system fails, usually it is from a clog ---> increased crankcase pressure ---> oil leak past the seal etc.

The video you posted above is from a different mode of failure: too much suction. Funny enough, this is exactly what you want in an M54 engine to reduce oil consumption.
The "BavarianE39 mod" is exactly that: creating a lot of suction to reduce oil loss from leaky piston rings.
 

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Discussion Starter · #80 ·
This was from my 2001 530i, it had a failed CCV and the dipstick tube (original non-updated version) was clogged
Do the BavarianE39 CCV mod (in Xoutpost forum) and move on.
It has been a few yrs and 10K miles since I did the CCV Mod on my 2006 X5 3.0i: oil consumption went down to zero, unbelievable mod (it used to consume 1 qt of oil per 400 miles!!!).
 
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