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1993.5 S4 green crankcase breather


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Late reply,


The inside our breather (red) of our 1988 is nothing more than a screen with a rubber flap inside. By design, it allows airflow (pressure) one way, but not the other.


I've taken them apart and found the flaps were malformed by oil fumes and would not close.


Because there is rubber inside, I would carefully and completely rinse out the inside with water after cleaning with anything that might further deteriorate the rubber flaps.


Atwell Haines

'88 Esprit

Succasunna, NJ USA

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Hi Atwell,thanks for reply. Used an inspection camera to look inside, cannot see much but have attempted to upload what I could. Little evidence of a rubber flap and I can blow through in both directions and there doesn’t seem to be any difference.

My part number is A912E6802F crank case breather valve,I couldn’t find it on SJ sight. It has Milofiltre written on it. My S4 is 1993.5 you say yours is 88, are they the same?If so how did you get it apart and back together again and/ or another source. Thanks again2C1A48DB-C6D7-4043-B2A2-F05D3C707A50.thumb.jpeg.cc2a9467434d1040777ca51b16760eb5.jpegD2D33B62-F757-4EBE-9211-95361CE36E55.thumb.jpeg.ed01cfb02b54e9c2a760938976f19812.jpegDEB40E9F-2CB6-4294-B77E-911B96343958.thumb.jpeg.e1cacb58c3580edab53f7a37b1040aa3.jpeg in 

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7 hours ago, stevefh said:

please tell me how you got yours apart and back together.

It was Soooo long ago....🙄


I might have just looked through the outlet opening after removing it from the car. Sorry.


Your second picture shows the shape of the flaps on ours. I don't know the difference in specification.


We DO get a bit of oil in our air filter housing from crankcase pressure. Because of that, we clean our Bosch fuel metering flap at least yearly.

The purpose of the red (or green) part is to limit the flow to one direction (OUT of the crankcase) It's a Positive Crankcase Vent valve, after all.



The PCV system draws leftover combustion gases from the crankcase (the oil pan and bottom of the engine) and routes them back into the engine via the intake manifold or air filter housing, where they're burned in the combustion chambers instead of escaping into the atmosphere via your exhaust system.


Atwell Haines

'88 Esprit

Succasunna, NJ USA

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It is rebuildable. It contains a number of mesh screens inside (make sure you pop em back in the same way once you've brake and clutch cleaned em. It's a very crude but seemingly quite efficient design and never fails causing billows of smoke like the far more modern and complicated Porsche AOS devices.

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  • 4 months later...

Scuderia, that's very good to know as cipere seem to be the same group as der franzose who over the years I've used a lot for Renault bits for my Europa without any issues and they usually ship next day.

At that price will probably get one as a spare next time I order from them.

Here is the same link on the english language site for der franzose


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