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Hello All!

I have a terrible squeal (like a tea kettle about to blow) coming from my engine bay (986).  I have since, eliminated the pulleys and belt as the problem and finally discovered that opening the dipstick to release vacuum pressure stops it.  Also, when I turn the engine off I can hear the squeal wind down and "weeze" out.  I guess thats good because I was worried it was metal on metal.

Im not sure where to start poking.  Its very loud and I cant seem to pinpoint it.  Im thinking maybe the AOS?  No codes, no performance issues...yet.  Anyone ever experience this issue?  I have attached a link with a video of the problem.  Be prepared...its loud.


See the problem here.



Thanks to all in advance...


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Your tea is ready :)


Kidding aside, you can use a mechanics stethoscope to poke around (but be careful of poking near the engine rotating parts). It's likely the AOS.



Or a more sophisticate one here http://www.amazon.com/STEELMAN-97220-EngineEAR-Diagnostic-Listening/dp/B00396FBRY/ref=sr_1_7?ie=UTF8&qid=1459817163&sr=8-7&keywords=mechanics+stethoscope

With this device, you can trace the source of the noise based on its intensity when you move the probe around in the air.

Edited by Ahsai
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To check if its the aos, with motor warm and idling take off the oil cap and put your hand over the opening and seal it gight. You should feel the slightest vacuum. If there is significant vacuum the problem is the aos and the sound you hear is air getting sucked past the rms. If thats the case dont even start the car. You could very easily suck the oil out of the crancase into the intake leading to hydrolock which will ruin your motor.

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@san rensho,

Yes, the vacuum is very significant.  I could not even get the oil cap off while the car was running, and I don't ever remember it being that strong.  Thank you all for the input.  Unless anyone else has other ideas, I will start with the AOS and report back (hopefully with a solution) for future members who may have this issue.

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  • 2 years later...
  • 7 months later...
  • Admin

Easy enough to test - remove the drive belt and run the engine for a few seconds if the squeal goes away then it is something in the pulley system.

If it does not go away then you need to look at other potential causes: bellow leak at the bottom of the AOS, cracked oil filler tube, or serious internal engine issues.

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