15 captured repliesDiscussion pagination complete · Source accounts, not a confirmed diagnosis
THIS DISCUSSION / SOURCE-DERIVED OVERVIEW
Discussion summary
YOUR RESEARCHSquealing from engine bay
Leading reported evidence
Replace idler
Performed · outcome unconfirmed
No successful repair reported for this finding.
0
Reported fixes
0
Unsuccessful attempts
1
Discussions
Read evidence and context
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.
Discussions that performed work without a confirmed outcome
1
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0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
I suspected an AOS failure and replaced a relatively new AOS, 1k miles on it, and changed an idler that seemed suspect.
Leading evidence: 'Replace idler' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Check when i return (im traveling now)' (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.
Source reports, not a diagnosis or a success probability. Counts refer to discussions and can overlap.
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.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
I suspected an AOS failure and replaced a relatively new AOS, 1k miles on it, and changed an idler that seemed suspect.
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.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
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.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
I have now ordered a new water pump and will replace it soon, but I know that's not causing the squeal as I hear it when I run the engine without the belt on.
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.
Discussions that contain suggestions
1
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Suggestion · Original poster
I will be sure to check when I return (Im traveling now).
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Unsuccessful attempt · Original poster
I recently changed spark plugs and will verify fit, but I looking for some help on what to do next to diagnose this issue. The AC load also makes no difference to the squealing.
Discussions that performed work without a confirmed outcome
1
0 original-poster resolution reports. Counts can overlap; they are not unique people or a success rate.
0 discussions have direct query context; 0 report a fix in that context. Other evidence may inherit the discussion’s subject.
Performed · outcome unconfirmed · Original poster
I have now ordered a new water pump and will replace it soon, but I know that's not causing the squeal as I hear it when I run the engine without the belt on.
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.
15 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.
0 acknowledgements have no verified action link; they do not establish a repair result.
Generation: 20261026T200546Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
A couple of weeks ago my 996 C4 developed an intermittent engine squeal that used to manifest itself under load. It used to be faint and was only audible once in a while on a cold engine, but recently it started to occur continuously irrespective of engine temp and load. I suspected an AOS failure and replaced a relatively new AOS, 1k miles on it, and changed an idler that seemed suspect. I also changed to a new belt without any luck. I have now ordered a new water pump and will replace it soon, but I know that's not causing the squeal as I hear it when I run the engine without the belt on. It appears to come from the lower right side of the engine. I recently changed spark plugs and will verify fit, but I looking for some help on what to do next to diagnose this issue. The AC load also makes no difference to the squealing. I cannot remember correctly if turning the steering wheel has any effect, with the steering wheel pump in mind. The suspension and brakes can be ruled out as the noise is audible when the vehicle is stationary. I have a replacement piston for the oil pressure release valve and have planned to replace it before the new year.
Thanks in advance!
2000 996 C4 (Getrag front drive deleted) with 15x,xxx mi, replacement engine with larger single row IMSB from '09.
Things worked on recently:
Coolant flush and refill
AOS
Upper Idler pulley
Serpentine Belt
Spark plugs
Replaced all vacuum lines in the intake circuit
MIL:
Appears for Secondary Air Pump (vacuum lines had a leak, haven't seen this after replacing all lines in the intake circuit)
It squeals with the belt off? That is not good news at all. In the vicinity of rear lower right side is the scavenge oil pump. If that squeals, you have serious problem. I would drain the oil, remove the scavenge pump and inspect it.
Did it squeal prior to doing the spark plugs?
I've seen posts where a loose spark plug can make a squealing sound as air passes the threads
that might make since as it first started under load, then got progressively worse
I also had a chirping sound that was a loose baffle in the exhaust can
some well placed spot welds fixed that
Thanks for the replies,
I am no longer driving her. Only fixing things and turning her on to see if it worked. To my recollection, the noise wasn't a problem before the plugs, and I am hoping that it's only the plugs. I will be sure to check when I return (Im traveling now). I know Porsche recommends not to add any anti-seize, and I have not.
This happened to me....after of all things a PPI....drove me crazy until another mechanic figured out the plugs were never tightened. Sound went away for good.
Hey all,
It brings great peace to my mind to learn that Cyl 4 plug was slightly loose. I retightened the plug and the squealing went away. She runs better than ever.
Thanks for all the help!
