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Whistling noise from engine compartment after 20 minutes driven from cold start

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Original source

5 captured repliesPartial discussion capture · Source accounts, not a confirmed diagnosis

THIS DISCUSSION / SOURCE-DERIVED OVERVIEW

Discussion summary

YOUR RESEARCHWhistling noise from engine compartment after 20 minutes driven from cold start

Reported or suspected cause

air oil separator

Reported cause

No successful repair reported for this finding.

1
Identified cause: 0
Suspected cause: 0
Reported fixes

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 report identifying a cause: 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.

Reported cause
Therefore I'm not quite sure whether it is caused by AOS.
Original post Read captured discussion
Whistling noise from engine compartment after 20 minutes driven from cold start

Frequently discussed work

Run i still can open the oil cap

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 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.

Suggestion
Referring to some AOS failure post, there's no white smoke when I start the engine, also whilst engine running I still can open the oil cap.
Original post Read captured discussion
Whistling noise from engine compartment after 20 minutes driven from cold start

Read full discussion summary

Leading evidence: 'air oil separator' (1 discussions report identifying this cause; no attributable repair resolution). Across 1 matching discussions, the most frequently mentioned possible cause is 'air oil separator' (1 discussions; 1 report identifying it and 0 suggest it). The most frequently discussed action is 'Run i still can open the oil cap' (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.

Read captured replies

1 matching discussions · 5 captured posts examined · 1 partial discussions

Compare 3 other evidence results

gearbox coolant vacuum disc valve 928 574 573 03

Reported cause

No successful repair reported for this finding.

1
Identified cause: 0
Suspected cause: 0
Reported fixes

Read evidence and context

Discussions that report identifying a cause: 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.

Reported cause
Just get my car checked and found the issue is with the Gearbox Coolant Vacuum Disc Valve 928 574 573 03, which is the also mentioned in another thread:
Original post Read captured discussion
Whistling noise from engine compartment after 20 minutes driven from cold start

oxygen sensors

Reported cause

No successful repair reported for this finding.

1
Identified cause: 0
Suspected cause: 0
Reported fixes

Read evidence and context

Discussions that report identifying a cause: 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.

Reported cause
and it turned out to be an oxygen sensor.
Original post Read captured discussion
Whistling noise from engine compartment after 20 minutes driven from cold start

Run i still can open the oil cap

Suggestion or failed attempt

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 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.

Suggestion
Referring to some AOS failure post, there's no white smoke when I start the engine, also whilst engine running I still can open the oil cap.
Original post Read captured discussion
Whistling noise from engine compartment after 20 minutes driven from cold start

Frequently discussed actions (1)

These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.

Run i still can open the oil cap

No successful repair reported for this finding.

0
Reported fixes: 0
Unsuccessful attempts: 1
Discussions

Read evidence and context

Discussions that contain suggestions: 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.

Suggestion
Referring to some AOS failure post, there's no white smoke when I start the engine, also whilst engine running I still can open the oil cap.
Original post Read captured discussion
Whistling noise from engine compartment after 20 minutes driven from cold start

Reported and suspected causes (3)

These are separate views of the same evidence. Frequency alone does not establish a fix, and these counts must not be added together.

air oil separator

No successful repair reported for this finding.

1
Identified cause: 0
Suspected cause: 0
Reported fixes

Read evidence and context

Discussions that report identifying a cause: 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.

Reported cause
Therefore I'm not quite sure whether it is caused by AOS.
Original post Read captured discussion
Whistling noise from engine compartment after 20 minutes driven from cold start

gearbox coolant vacuum disc valve 928 574 573 03

No successful repair reported for this finding.

1
Identified cause: 0
Suspected cause: 0
Reported fixes

Read evidence and context

Discussions that report identifying a cause: 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.

Reported cause
Just get my car checked and found the issue is with the Gearbox Coolant Vacuum Disc Valve 928 574 573 03, which is the also mentioned in another thread:
Original post Read captured discussion
Whistling noise from engine compartment after 20 minutes driven from cold start

oxygen sensors

No successful repair reported for this finding.

1
Identified cause: 0
Suspected cause: 0
Reported fixes

Read evidence and context

Discussions that report identifying a cause: 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.

Reported cause
and it turned out to be an oxygen sensor.
Original post Read captured discussion
Whistling noise from engine compartment after 20 minutes driven from cold start

Coverage and how to read this overview

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.

5 eligible posts · 0 unverified posts · 1 discussions match the subject in their title or opening post.

Planet-9: 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: 20261026T130754Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources

POST 1Original post

Hi Guys, 2 weeks ago I started to experience the whistling noise from Boxster 987 10MY 2.9L. During the first days, I notice it only after I arrive at destination and turned off engine, there's a whistling fading out in 5 seconds. Recently the noise is more sensitive and I can hear it during driving. On a cold start everything goes normally, after 20 minutes driving(engine temp. already reached normal in first 5 minutes or so) the noise starts to come up, at the beginning it can only be heard when I open the window, but later it becomes much louder, it persists no matter what speed I'm driving or engine idle. When the issue occurs, after restart the engine, the noise come back after about 5 seconds. By ignition on but engine off, there's no noise. I've recorded a video which is after 40 minutes driving this morning and the noise is quite loud. https://youtu.be/OYH_w5AdnNQ Referring to some AOS failure post, there's no white smoke when I start the engine, also whilst engine running I still can open the oil cap. Therefore I'm not quite sure whether it is caused by AOS. Some key observations: - Issue come up after 20 minutes after cold start - Issue come up after about 5 seconds after warm start - Noise fade out in 5 seconds after engine off, but not cut off immediately when engine off - Noise become more and more louder during driving Anybody have any thoughts? Is it something to do with AOS, or shaft oil seal? Thanks~

POST 2Original post

One thing you must consider is the water pump. They make all kinds of weird noises when they start to go. Mine sounded like a 727 during takeoff. Good luck.

POST 3Original post

Engine cooling fan? Mine started to go bad and it sounded like I had a vacuum cleaner running in my engine bay.

POST 4Original post

-- I recall similar with the Cayman S and it turned out to be an oxygen sensor. The water pump and belt roller bearings make more of a loud whining noise when they begin to fail...

POST 5Original post

Just get my car checked and found the issue is with the Gearbox Coolant Vacuum Disc Valve 928 574 573 03, which is the also mentioned in another thread: https://www.planet-9.com/987-cayman-and-boxster-chat/200609-diagnosing-squealing-noise.html

This is a source reference. Confirm exact model applicability in the original material.