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Whistling noise above 30 mph

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I recently noted that at speeds above about 35 mph my boxster starts to whistle; appears to be coming from the right side of the car.

The noise does not get louder, but continues until the car slows below about 30 mph.


Other threads have indicated that changing the fuel vent valves would resolve the issue.

I have changed both of those, and if anything, the noise has gotten worse (starts at a lower speed than before).


Does anyone else have any suggestions?
IT appears this is not a unique problem to my car as many others have posted this same issue.

However , I've never seen any posts that specifically say what was done to fix the annoying squealing noise......


Thanks for any help/ suggestions!!!

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Door/window seal?  Gummi Pflege might be worth a try.


P.S. You haven't mentioned the age of your car, but I see that you later refer to the sound as "squealing".


A small tear in the AOS diaphragm? There's a simple test if you haven't got smoke from the exhaust. From memory, start the car and then remove the oil filler cap. There should be little resistance in removing the cap, and a small amount of suction.


You might want to verify that procedure. 

Edited by wizard
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Thanks for the additional option.

My Boxster is a 2002 with 78k miles. The sound is heard with top up or down and only starts when the car gets above about 35-40 mph, and is definitely coming from the right side.
As stated, I changed both fuel vent valves a few weeks ago per another post from a few years ago; but it didn't fix the problem.


Since it only happens when the car is "under load"/ driving, I'm puzzled even more.

I'll see what I can find on the AOS diaphragm and check that then report back.... thanks! 

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9 hours ago, txhokie4life said:

On one car there was a valve I had to replace under the intake (drivers side).  It would make noise around the gas cap area as well as throw the random CEL from time to time.


That would be the EVAP system purge valve, which connects to the canister next to the gas filler tube.

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I tried bypassing the AOS over the weekend, and the noise remains, no change so will reconnect it ASAP.
I did note that car runs much better without the AOS connected though!


Thanks for the continued support in my efforts tracking this down.


I'll check the EVAP purge valve and read through the link above tonight.



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thanks for the continued support in my chase....
I'll look into the EVAP purge valve (s)?
So to ask another question, are there really 2?
One at the EVAP tank and another on the drivers side intake?? if so, should both be replaced??



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