weird engine sound, with great quality youtube clip

You Tube it randomly occurs, and when it does it stays for about a minute then goes away.. can occur once a day or a couple times, at different times/hours. Never hear it in the freeway cause engine's too loud so who knows if it's occuring or not. you hear it a little when i gas it but it sounds the highest when i let off the gas. sounds like a turbo blow off haha anyone know what it is or what causes it?? thanks! i am completely CLUELESS the sound I'm talking about is heard most clearly as my foot gets off the gas pedal (as the RPMs are spooling down)

Sounds like a healthy engine to my ears.....

Sounds like a rattle to me... perhaps a heat shield on the exhaust loose?

you have something loose somewhere, certainly a bolt getting loose and a washer playing in the middle. could come from anywhere but check the exhaust line first, plenty of bolts there that could come loose and create a noise that would change with RPM. strange that you don't have it all the time though..

Sound's like a intake leak. If you mean that "scoooohh" sound after you lift the throttle?

Timing chain lash maybe. (Tensioner or IMSB?)

yes the sound as soon as i lift the throttle, that winding down sound

Put me down in the sounds normal camp too. However, noises are hard to diagnose even at the car. Have you had a professional tech give a listen? Sincerely, Macster.

air leak gets my vote try standing next to the engine and listening while someone else revs....you'll get much closer to the source

i'll have my indy look/listen when i go in for oil change in a week i'll keep u updated. but do u guys actually hear the winding down whoooosh?

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Hope I'm right but I hear nothing out of the ordinary. There could be a whooshing sound, but I do not hear it. Have to point out the engine's running at some high(er) rpm, then the throttle is closed. This creates a big vacuum (well, low pressure) in the intake system, from the TB and its butterfly valve on. This low pressure -- part of it anyhow -- is used to help remove air from the crankcase. The crankcase might have some higher pressure due to the engine running at higher speeds, from blow-by and coupled with higher pressure in the intake system, which can approach atmospheric under WOT conditions. Thus the whoosh sound could be the sound of crankcase air 'whooshing' through the AOS, which is plastic, sits up on the engine and could radiate/emit the noise you report hearing. Also, the whoosh could be hydraulic power steering fluid coursing through the hoses. Be safe, though, and let an expert listen to the noise. Sincerely, Macster.

thanks so much

After turning up the volume I could hear that semi rattle or chain clacking noise on letting off the throttle. Wouldn't hurt to take the air cleaner off and survey on top plus check under the car like was mentioned for heat shield being loose. Just something to do while the engine is cold with lots of everything in there to finger around with and wrench a little to see if there is something loose. I'm also thinking it's reflected noises off concrete and walls playing games since you possibly wouldn't hear the noise on the road.

It sounded normal to my ears as well, you guys are starting to make me paranoid...

Its defo the IMS going to explode hahaha. Only kiddin. I must admit I am always listening to my engine as well and imagining things. Very rareley do I drive with the radio on. I had the top down the other day and God forbid I was travelling next to an unseen railway line with good carraiges moving slowly. I was consentrating on the road with an ear open on the engine sound and an eye on the dials when this train must have pulled to a halt and the goods wagons clanged together and I almost **** myself. "For frankfurters sake" I thought to myself. I thought my engine had fallen out. hehehe You might be as well asking an indy for a second opinion as some of us can't hear anything wrong. We probably could if we were stood behind the car with the lid opened. Anyway hope all turns out well for you.

It's difficult to say for sure, but I heard something similar in a Boxster that had chain tensioners that were going bad. Then again, might be nothing. Get a good mechanic to listen to it.

I'm shocked no one tried blaming it on the IMS bearing lol

Turn the aircon off completely and see if you still hear the noise?

bang on the cats... see if its coming from there.

i have no idea what the aircon is lol

I hear something that sounds like a mix between sleighbells ringing and air escaping when you let off of the throttle. Have you gotten underneath it or opened up the engine compartment while someone else tapped the throttle? That might help you isolate the source and help determine whether it's just a normal mechanical sound vs. the sound of something wrong. -Eric

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I believe he's referring to the air conditioner. -Eric

I can hear something that sounds like a mix between sleighbells ringing and air escaping when you let off of the throttle as well. You haven't ran over a big fat fellow wearing a red suit and hooded top have you. lol. Did you feel a bump and someone shouting out HO HO HO?

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I was wondering whether he may have seen a red glowing light on the ground after feeling a bump but was afraid to ask. -Eric

Well, the "odd" sound I heard from the clip was the rattle when the engine spooled down. My GUESS is that it could be the beginning of a baffle going bad in one of your mufflers or maybe a piece of honeycomb loose in the catalytic converter. The fact that it only does it for a while means to me that it is HEAT related - when cool maybe not so much, when warm it may happen, and when hot not so much again. When my original stock right rear muffler started to fail due to dying welds, it also acted the same way. And the RPM is what rattled it when the heat of the muffler was in its "sweet spot". Later it just rattled louder all the time. It also could be one of the dozen odd rotating bearings driven by the sepentine belt.