Cute little trick to diagnose blocked CCV system...
424083
91
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
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
1 - 10 of 10 Posts
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.
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.
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?
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?
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?
Thanks.
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.
![]()
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.
Attachments
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.
![]()
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.
Attachments
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.
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:
And this for the M54:
1 - 10 of 10 Posts
