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YOUR RESEARCHCan a leaking AOS breather tube cause a vacuum leak?
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Install aos primary last yr, seemed
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Performed · outcome unconfirmed
Installed new AOS primary last yr, seemed to get better but recurred.
Can a leaking AOS breather tube cause a vacuum leak?
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Leading evidence: 'Install aos primary last yr, seemed' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Install aos primary last yr, seemed' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Can a leaking AOS breather tube cause a vacuum leak?
Replace secondarys too this time i guess
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Can a leaking AOS breather tube cause a vacuum leak?
Run from the aos, you will eventually get codes
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Suggestion
If you have leaking hoses running from the AOS, you will eventually get codes.
Can a leaking AOS breather tube cause a vacuum leak?
Use intake vacuum as its source
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Suggestion
The AOS is a glorified PCV device that pulls a controlled 5 inches of water vacuum on the crankcase using intake vacuum as its source, to help the low tension piston rings maintain a proper seal.
Can a leaking AOS breather tube cause a vacuum leak?
Use intake vacuum as its source
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Suggestion
The AOS is a glorified PCV device that pulls a controlled 5 inches of water vacuum on the crankcase using intake vacuum as its source, to help the low tension piston rings maintain a proper seal.
Can a leaking AOS breather tube cause a vacuum leak?
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I've never really quite understood the whole AOS system so please excuse my ignorance in this question.
I have a breather hose related to the AOS that is leaking oil onto the right side of my engine. My mechanic said that as the leak worsens, it will likely cause a CEL due to vacuum leak. Can someone explain how this would be? My basic understanding is that clean air flows into the AOS device and into the crankcase (from somewhere?) and the polluted air in the case flows out, has the oil separated out and is sent back into the intake. I'd like to better understand the system but can't find any information out there.
My assumption here is that the leaking hose is pulling air from the crankcase into the intake, and that the leak would allow excess air in creating an overly lean mixture and triggering a CEL... but that's just a guess. Understanding what all the connections involved actually are would be a big help for me.
Thanks everyone.
Your assumptions are incorrect. The AOS is a glorified PCV device that pulls a controlled 5 inches of water vacuum on the crankcase using intake vacuum as its source, to help the low tension piston rings maintain a proper seal. It is not a "flow through" device, it is designed to hold the low vacuum while preventing oil from being sucked into the engine, which could cause hydro locking and total engine failure.
If you have leaking hoses running from the AOS, you will eventually get codes. Change the hoses, they are not expensive.
Got it, thanks JFP. Any insight on the various connections from the AOS and where they go? At least one connection must go back into the intake. Are there connections to flow the separated oil back somewhere?
One line goes to the intake (vacuum source), one each goes to each cylinder head (where the vacuum is applied), and a line for coolant on a 996 (Boxster does not use these). Entrained oil drains back into the side of the engine case and into the sump.
Trying to understand this myself on an 08 C4S. Installed new AOS primary last yr, seemed to get better but recurred. Oil in intake again. Will replace secondarys too this time I guess.
I did find a loose AOS hose where it returns to the intake. Low vacuum from a leak like that wouldnt cause the oil to be sucked into the intake, would it?
