plynchy Posted February 13 Report Share Posted February 13 This is somewhat theoretical, and I'm more than happy to be corrected on the operation of this mysterious blob of plastic that can cause a major headache for 986 owners. I've recently changed the AOS on my Poverty Pork Boxster, believing it had failed, but to cut a long story short it appears the issue has been oil overfill, rather than AOS failure, oil level was sitting one bar from the top of the dash scale. My write up relating to this is in the "Running Reports' section. I couldn't find an answer online as to how the AOS operates, so opened up my 'old' one to see what mysteries lie within, expecting a load of baffles etc, but it's nothing of the sort. Diaphragm cover removed, pipe on right goes into crankcase (oil return?), ridged pipe on left fume take off from crank case. Bottom section viewed from top, nothing complicated here, 2 empty chambers. Top section viewed from below, lower take off goes to cam cover vent. Diaphragm removed reveals a tension spring, which I assume holds the diaphragm in place vs induction vacuum, which attaches to hose top right. Dirty side of diaphragm also has a sprung relief valve, which again I have to assume can be overcome by crank case pressure to relieve excess oil pressure as and when this may occur, allowing the dump of oil into the induction system, creating the smoke bomb that 986 owners experience on occasion. The assumption is when this occurs that the AOS is kaput, but I couldn't find anything wrong with this one. Diaphragm is intact, springs are still good, and those are the only moving parts in it. Hope this sheds some light and is useful to someone. 🙂 1 1 Quote Link to comment Share on other sites More sharing options...
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