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Cute little trick to diagnose blocked CCV system...

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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.


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.
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Great explanation RDL, but I disagree with one part of your analysis. I think the diaphragm in the CCV is operated by intake manifold pressure rather than crankcase pressure.

I cut a CCV apart and found a couple of interesting issues. First, the bottom part, which I call the cyclonic separator, and the top part, which I call the regulating valve are connected with a small tube. This is the tube with the vacuum nipple that controls the FPR on earlier models, This tube is hollow, but extends all of the way through the cyclonic separator and is the part to which the drain tube (vent hose) is attached. This tube is continuous from the regulating valve to the drain tube and is only perforated by a few slots just above where the tube exits the bottom of the cyclonic separator..

Also, the web inside the cyclonic separator is a continuous spiral. The outside of the spiral attaches to the cyclonic separator body at the entrance of the vent pipe. The inner part of the spiral web is attached to the central tube.

The central tube connects to the regulating valve on the same side of the diagram as connecting line to the intake manifold. Inside the regulating valve the diaphragm works in opposition to a spring on the vacuum side of the diaphragm. So the diaphragm that closes off the passage of gasses from the cyclonic separator is exposed to vacuum from both the crankcase and the intake manifold.

I think the intake manifold vacuum will always be higher than the crankcase vacuum. So I think the diaphragm opens when the intake manifold vacuum is lowered(is closer to atmospheric pressure) as the throttle plate opens. This mode of operation would route the blowby gasses into the intake manifold when engine speed is high and air intake volume is high.

Since there have been so many questions on the topic of CCV operation and failure, here is a description of how I think the CCV operates using Bluebee's picture for reference.

The vent pipe, swirl labyrinth chamber and vent hose are always at the same pressure or vacuum - there is no valve or obstruction between them. The swirl labyrinth is the lower part of the CCV assy that the vent pipe & vent hose connect to. Further, they connect to the valve cover & crankcase without restriction and are at crankcase pressure/vacuum.

The connecting line and return pipe connect to the inlet manifold which has a vacuum of ~20 inches Hg (mercury) at idle; ~260 inches water column vacuum.

The portion of the CCV immediately beside the blue "CCV" label in Bluebee's picture is a vacuum regulator whose job it is to maintain 4 -6" w.c. vacuum in the swirl chamber.

When the engine starts, the labyrinth is at 0 vacuum (i.e. vacuum is less than 4" w.c.) & the orifice/valve in the regulator is open. The gases in the swirl chamber flow through the regulator into the connecting line (which is at high vacuum), on to the inlet manifold and through the engine. Soon the vacuum in the swirl chamber (also the crankcase to which it is connected) is sucked down to 4 - 6" w.c. vacuum and the orifice valve in the regulator closes.

The engine runs, more blowby gases from the combustion chamber enter the crankcase & raise the pressure (reduce vacuum) in the vent pipe & swirl chamber. The regulator opens again, allows manifold vacuum in the connecting line to suck them away until crankcase vacuum is back to 4 - 6" w.c. at which point the regulator closes again. And on it goes, cycling over and over.

As the blowby gas travels through the engine toward the CCV, it picks up microscopic droplets/mist of oil. We don't want this oil mist to go through the vacuum regulator, into the inlet manifold and be burned: high oil consumption and air pollution. Enter the swirl labyrinth; it causes oil droplets/mist in the blowby gases to stick to the wall of the labyrinth and drain down the vent hose into the dipstick tube and sump while the "cleaned" gases carry on through the regulator.
This is where we disagree. As I recall, the vacuum from the intake manifold and the crankcase are applied to the same side of the diaphragm. I do not remember seeing any part of the diaphragm that was molded to fit the tubes or any sort of special port. Just a diaphragm that moves against a spring to close off those two ports. Anyway, I'll take another looks at the diaphragm.

BTW, I was thinking about measuring the vacuum that must be applied to the CCV to close the diaphragm. Have you done that or do you have any advice about how to measure the vacuum required to close the diaphragm?
6 Next, blowby getting past the piston rings enters the swirl chamber & moves up into the regulating valve chamber which reduces the vacuum.
7 With reduced vacuum, the spring is able to move the diaphram and open the vacuum port to the inlet manifold again
8 Vaccum inside the chamber is again sucked down - around & around it goes.,,,
I looked at the diaphragm again. I can confirm that the diaphragm does indeed close off the vacuum to the intake manifold and that the crankcase vacuum is not closed off by the diaphragm when the the diaphragm is closed. I'll post a few pictures later today.
Do you know the pressure at which the diaphragm closes?
As someone who is currently involved with a redesign of the CCV, and studied the system extensively, I can tell you that rdl is 100% correct in his description of how the system functions. In fact it is by far the best technical description I have seen to date.

Good job.:thumbup:


Here are two photos.

The first shows the opened vacuum regulator. This shows the diaphragm, the spring and the case. Note that the diaphragm seals off the hose going to the intake manifold, but does not seal off the central tube that allows gases to flow from the oil separator. The central tube and oil separator are at crankcase pressure.

The Second photo shows the oil separator of the CCV. I passed a red wire around the spiral to show the path of the gasses and show that it is a spiral. Note I drew the yellow line to show the inner edge of the spiral web on the oil separator. The oil and gasses enter from the left and travel along the spiral path until it reaches the central tube.

I think we are all on the same page here. The diaphagm isolates the manifold vacuum (approx 260 inches of water) from the crankcase once the crankcase vacuum reaches 4-6 inches of water. The diaphagm modulates opening and closing the port to the intake manifold which regulates the crankcase vacuum to 4-6 inches of water.



Sorry for the late reply - I just looked at this thread again.

Indeed I posted the same photo twice. I've posted the second photo below. It shows a section through the M54 oil separator part of the CCV.

I doubt this adds anything to the current discussion, but I wanted to post it for completeness.


It looks like both pictures that you uploaded are the same.

I'm still a little confused as to whether you agree with me and RDL on how the system functions, or if you are still taking an opposing view. I'm not trying to be sarcastic in any way, I'm just not sure if we are on the same page yet.




On the M54 the FPR is on the fuel filter. It's connected to the "F" connector on the intake boot.

I don't understand why a FPR would need an atmospheric reference.
...The M54 engine does not; it uses constant fuel pressure...
I never thought of it as a reference to atmospheric pressure. I've assumed that it was necessary too let the volume behind the diaphragm vary without restriction.

As I recall, in one type of FPR the return flow is blocked under low vacuum, such as acceleration. Another type of FPR actually increases return flow under high vacuum situations like idling. I suppose one could design a FPR to do both, but I've assumed that the FPR on the e39s are the second type that lower fuel rail pressure during high vacuum.

If I understand what you've written, you think that the FPRs on the e39s don't really use a vacuum source to move the diaphragm, only to vent area behind the diaphragm. Certainly the M54 FPR will not see a strong vacuum since it's connected upstream of the throttle. Assuming that the CCV is operating at crankcase vacuum, it would be insignificant for the M52, too.
I can't find the description of the M52 FPR operation in the online version of the TIS. Are you looking at another version? However, that is exactly how I assumed the M52 FPR worked. And that is why I assumed that the vacuum port on the CCV was operating at manifold pressure.
I found this about the M52 in the online version of TIS:

Description of operation: fuel pressure regulator
Depending on requirements, the fuel pressure regulator regulates a low or high fuel pressure. This requirement is set with the help of the pressure regulator.
Depending on the engine's operating state, less or more fuel is needed:
- at idle speed, less fuel
- at full load, considerably more fuel.
The injection rate is precision-adjusted by means of the injection time; the injection time is controlled by the DME.
The partial vacuum in the intake manifold serves as engine load information for pressure regulation. The diaphragm of the pressure regulator is actuated with this partial vacuum.
A partial vacuum builds up in the intake manifold during idling operation or in overrun mode. Depending on the partial vacuum value, the fuel pressure decreases starting out from the nominal value. The nominal value is stamped in the fuel pressure regulator housing.
At full load, the partial vacuum in the intake manifold is approximately equal to zero. The fuel pressure regulator regulates the fuel pressure to the nominal value stamped in the housing.
And this for the M54:

Description of operation:
The control function of the fuel pressure regulator must be guaranteed under all operating conditions. The fuel pump must always be able to generate a higher fuel pressure than the pressure regulated by the pressure regulator.
The injection rate is adjusted by means of the injection time; the injection time is controlled by the DME.
Description of operation: fuel return line
When the engine is at a standstill and the ignition key is in position 0, the fuel return line after the pressure regulator is at zero pressure.
Description of operation: pressure retaining function
The pressure regulator closes when the engine is at a standstill and the ignition key is in position 0. The fuel pressure in the delivery line is retained over an extended period. A non-return valve closes in the fuel pump. These measures help to retain the fuel pressure in the fuel system. Extended starting times are thus avoided.
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