17 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHWhen to Replace AOS ?
Leading reported evidence
Replace aos." do it
Performed · outcome unconfirmed
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0
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1
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Performed · outcome unconfirmed
When replacing the IMSB, RMS (tran out), no one has ever said, "I wish I hadn't replaced the AOS." Do it.
Leading evidence: 'Replace aos." do it' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Replace aos is easily less than an hour' (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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Suggestion
With the engine out, the actual time necessary to replace the AOS is easily less than an hour.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
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Suggestion · Original poster
I've read that add'l labor to replace the AOS is not too bad (1 hour?), so maybe a good time to consider.
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Suggestion
Also replace the hose that goes from the AOS to the opposite bank.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
17 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.
Rennlist: 1 discussions
0 evidence records excluded for query context · 0 excluded by outcome qualification · 0 adjusted by outcome qualification.
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Generation: 20261026T072535Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
1999 C2, original owner, 63k miles. Car going in next week for IMS/RMS/Clutch/Flywheel. I've read that add'l labor to replace the AOS is not too bad (1 hour?), so maybe a good time to consider.
Can anyone here offer advice as to whether this would be advisable, or just do as part of a cooling system overhaul (T-stat, pump, expansion tank) at a later date. I had an expansion tank blow on my old BMW, and it wasn't pretty......Thanks......
I would do it now. It is much easier to do with the trans out (don't need to remove the intake manifold). Doing it with the trans in from the top takes much more time. Figure $150 for the new part, and $150 for the extra labor, vs. 3-4 hours of labor later.
Thanks all for the sound advice! I love this forum!
Someday we'll play "who has owned their '996 the longest". I'll start a new thread for that one........
With the engine out, the actual time necessary to replace the AOS is easily less than an hour. I - who had never before set eyes on an AOS - did it in about 20 minutes. But I expect one hour is what a typical shop would charge for.
With the engine in the car, this job seems as if it would have to be frightfully difficult. I'd strongly recommend you have it done along with the other work.
I did mine preventatively with the engine installed, and if I had to do it over again I'd probably just drop the motor to do it. Very awkward and tight quarters. Doing it underneath with the transmission out should help. If they can do it for another hour plus parts, jump at it. No brainer.
I did the AOS when I did my IMS/clutch/RMS.
It was reasonably ok to do, but I found the little coolant hose connection a real PITA to connect back on the new one.
My AOS tested good while doing the IMS. Less than a month later, the AOS went out on me. Replace it now while it is easy to access! I can speak to how big of a pain it is to reach going from the engine bay rather than below with the transmission out.
