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V70 Positive Crankcase Ventilation.

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Old Aug 10th, 2020, 07:17   #1
emtor
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Default V70 Positive Crankcase Ventilation.

2008, V70.
Engine: D5244T5.

Bought a V70.
First thing I did was the PCV test with a rubber glove on the oil filler hole.
No surprise, the glove inflates at idle, pulling the oil level stick in order to help the engine getting rid of some of the over-pressure does not change this,-glove still inflated.
Revving the engine causes the glove to be sucked in slightly.
As I understand it, these Volvos have two different PCV circuits: -One for idle which uses vacuum from between the airfilter-box and the intake of the turbo, and one for higher engine RPM's which uses vacuum from the turbo.
So far so good,-but getting a thorough explanation on how this system works and all it's parts and hoses on youtube/google is not to be found.
So my question is;-is there anyone here with knowledge enough to be able to explain how the PCV-system works so that I can diagnose the problem properly?
Of course, I could always throw parts at the problem, and why not buy a brand new Volvo while I'm at it . . . diagnosing first and then buy parts is better.

Last edited by emtor; Aug 10th, 2020 at 08:52.
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Old Aug 10th, 2020, 10:50   #2
37 RUBY
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There are 2 circuits.


Idle circuit - Intake manifold provides the vacuum source during idle.
As per the rest you conducted by putting a latex rubber glove over the oil filler hole with the engine idling, if the rubber glove gets a little air sucked out of it, there is vacuum and a healthy unclogged idle circuit. If the rubber glove blows up, like yours, then there is little or no vacuum and you potentially have a clogged idle circuit.

Boost circuit - Intake manifold on turbo charged cars switches from vacuum to pressure under boost so can not be used as the exclusive source for vacuum like normally aspirated cars. There is a vacuum source in front of the turbo called the PTC nipple(Positive Temp Coefficient = PCT) that provides vacuum under boost conditions. The PTC nipple also has an electrical connection to power a heater in the nipple.

Another potential issue will be a failed PCV itself. That is usually accompanied by a loud ticking noise that stops or reduces when you remove the oil cap.

Hope that helps...
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Old Aug 10th, 2020, 12:26   #3
emtor
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Thanks for replying,-the info is useful indeed.
I have another question,-what is this part?

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