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Homeland Security
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87 Posts
Discussion Starter #1
Hey everyone, just wanted to introduce myself since i'm new to this forum. First off, i'm a proud owner of a 2000 2.4 altima gxe, with 93000 orginal miles. I though thought of trading it in for an STI since i'm now making some dough. But i just still can't seem to let it go, since it runs great, gets 29 mpg, and the fact that insurance rates are rediculous here in NJ. No matter how many small glitches it has, its still a damn good car.

So here i am, after lurking for a little bit, i realized that you guys a great group of commited and helpful alti fans, and wanted to join in on the club.


So now that introductions are out of the way, i'll get to the point...


About 8 months ago, and 5000 miles less, i began to hear a hissing sound between 3000-3300 rpm then subsides at higher rpms(like a switch - noise fades out real quick), it sounds like a very mechanical hiss, that can best be described like the sound of water hitting a wall at a high velocity. Its been getting louder as months go by, but subsides a tad once the engine warms up. I know the ka24 is a lound engine by default, but this his is loud enough to startle people in the cars beside me. No matter what speed i'm going at, the hiss occurs at the indicated rpm range. The car runs fine, and still gets 27-30mpg with mixed summer driving. When investigating the sound, the sound seems to come from the pulley side of the engine, but i'm unsure why it only happens at a specific rpm.

I'm just worried if it might be something serious down the line. Thanks for the help guys and gals!



BTw- sorry the sound clip came out horrible, the engine revs drowned out the hissing in the audio clip, so no point in posting it
 

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Lookin' for a hooptie
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1,125 Posts
IM in a rush at work but i could guess a crack in your intake somewere or a hole.

I have a CAI and that rpm range makes me hear a pretty cool sounding suction noise. Sometimes i will rev in that range just to hear it over and over lol..
 

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Captain Obvious!
Joined
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874 Posts
I'm thinking its either your intake, or it could be a peice of heat sheild somwhere.
I had the issue on my 240sx where it would get that type of noise at only a certain rpm....trimmed the part of the sheild and no more noise.
As for my Alty, i do have some amount of hissing...but i know that mine is from the intake.

hope this helps some.
 

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Homeland Security
Joined
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87 Posts
Discussion Starter #6
I don't think its comming from the intake, i'm just wondering why it sounds like a valve is opening and then closing at that rev range, either way, i'm gonna take a look. Can any of th pulleys on the left of the engine(facing the car) make that kind of noise? I just hope it isn't serious. thanks for the input, keep it comming,
 

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Golden Member
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1,834 Posts
this isn't a/c related is it? turn that off to find out !
 

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Island Style
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598 Posts
As i said I have the same problem, but it sounds like yours is worst/louder. I mean it only happens at 3,300rpm and up in each gear but I ran diagnostic and had no errors at all. I never use my a/c either and it does it so it prolly isn't dat. What side is it comming out of?
 

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Homeland Security
Joined
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87 Posts
Discussion Starter #10
definatly not the ac, since it happens even if the ac is off. As for the intake, I checked it out, although stock, there seems to be no problem with it. It seems that ars & Braddahjon have very similar symptoms except in different rpm ranges. Is your sounds comming from the alternator side of the engine? No performance loss i'm assuming, just that annoying noise at that rev range.


The irony is that, i use to run the whole rev range before the noise gettin about 25 mpg, now i'm short shifting below 3000 to avoid that noise and pulling roughly 30 mpg hwy. Saving me a few bucks each time at fill up.
 

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Registered
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9 Posts
you said the noise is from the pulley side right....does it sould like a squealing sound cuz if it does then its probably a worn belt that needs to be replaces...

and for the people that hear the noise just after muffler instalation its prob just a leak sumwhere in the exhaust system...my last car did it after i put an exhaust on and one of the gaskets was bad so it did it all the time....
 

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Homeland Security
Joined
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87 Posts
Discussion Starter #13
loose heat shielding

After a few days at my mechanics shop, he discovered that the noise wasnt from the pulley, but instead came from loose heat sheilding at the bottom of the car, closer to the cat, he added a clamp, and just like that the sound disapeared... unfortunatly the car suffered the infamous idler pulley failure that same week
 
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