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Hissing sound from engine bay
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rafale_05
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Aug 22, 2013, 2:34 PM
Post #1 of 12
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Hissing sound from engine bay
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Car in question is a 2007 Nissan Altima 2.5S.
I'm hearing a weird hissing sound from the engine bay that intensifies with RPM. It almost sounds as if something is "caught" or is dragging on some rotating object. Here's what else I know so far...
1. The sound only starts emanating after about 15-20 minutes of driving.
2. The sound will momentarily go away if I park the car for about 5 minutes.
3. Seems to be coming from the left side of the engine bay (standing in front of the car looking at the engine bay).
I've tried popping the hood and looking inside while playing with the throttle cable, but by the time I park the car and start revving it, the noise is either too low to hear over the engine or is gone.
Anyone have any clues as to where I should start looking?
EDIT: I managed to finally get this sound on recording. Please turn your volume up and listen for a sound when I let go of the throttle: http://picosong.com/yq3t/. It seems to be the loudest after the third and last rev in the recording.
(This post was edited by rafale_05 on Aug 23, 2013, 3:52 PM)
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Discretesignals
Ultimate Carjunky
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Aug 22, 2013, 8:29 PM
Post #2 of 12
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Re: Hissing sound from engine bay
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Can you record the noise, upload it to a video hosting site, and then paste the link in here? Maybe hearing it can give us some clues?
Since we volunteer our time and knowledge, we ask for you to please follow up when a problem is resolved.
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rafale_05
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Aug 23, 2013, 12:10 AM
Post #3 of 12
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Re: Hissing sound from engine bay
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I've tried recording it, but the sound is so subtle that it can't really be heard clearly in a recording.
Just slide your hand across a wooden surface and you'll hear the exact same sound I'm trying to describe here.
Like I said before, this sound varies in intensity with RPM. The sound kicks in as soon as I give it some revs, but it's a lot more noticeable when I let go of the gas and let the engine rev down.
(This post was edited by rafale_05 on Aug 23, 2013, 12:12 AM)
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Tom Greenleaf
Ultimate Carjunky
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Aug 23, 2013, 3:21 AM
Post #4 of 12
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Re: Hissing sound from engine bay
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IDK - Can you take the belt off and quick run it and see if noise goes away? That would tell you it's a belt driven something going on so spin them by hand , engine off and see if one feels wrong,
T
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rafale_05
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Aug 23, 2013, 5:44 AM
Post #5 of 12
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Re: Hissing sound from engine bay
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I would try that, but this noise is very unpredictable. I've even tried pulling over as soon as I start hearing it and pop the hood to try and pinpoint its source, but it'll be long gone by the time I'm standing in front of the engine. I can rev the hell out of it by pulling at the throttle cable, but still nothing.
I just got back from a 50km drive, and I didn't hear a thing. The only difference between today's drive and yesterday's drive is that I didn't use the AC this time.
Is it possible for the AC to continue making noises even if it's turned off after 15-20 minutes of operation?
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Tom Greenleaf
Ultimate Carjunky
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Aug 23, 2013, 6:53 AM
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Re: Hissing sound from engine bay
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Quote: ">>
Is it possible for the AC to continue making noises even if it's turned off after 15-20 minutes of operation?<<"
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The normally make some sound of pressures equalizing if on when shutting engine off sometimes goes without notice. 20 minutes is a looong time though. Does the A/C work properly and as expected?
Maybe you are hearing normal water if just A/C that it makes that can drip to something hot (unlikely) but even that 20 minutes would be too long,
T
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rafale_05
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Aug 23, 2013, 12:28 PM
Post #7 of 12
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Re: Hissing sound from engine bay
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The sound isn't there after I shut the engine off. I can only hear it within the 3k to 5k RPM range, especially when the engine is revving down.
I'm now starting to think that this does indeed have something to do with the AC. If I use the AC for more than 10 minutes during a drive, I start hearing the noise. However, the odd thing is that once it begins, the noise will persist even if I shut the AC off.
I'm going to confirm this by driving home without the AC today in 86F weather.
(This post was edited by rafale_05 on Aug 23, 2013, 12:32 PM)
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Hammer Time
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Aug 23, 2013, 12:34 PM
Post #8 of 12
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Re: Hissing sound from engine bay
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Did you check all your heat shields and Converter?
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We offer help in answering questions, clarifying things or giving advice but we are not a substitute for an on-site inspection by a professional.
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Tom Greenleaf
Ultimate Carjunky
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Aug 23, 2013, 12:41 PM
Post #9 of 12
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Re: Hissing sound from engine bay
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Good idea despite those usually just rattle but who knows? OP - some you can find just tapping on exhaust with a rubber hammer to locate an elusive noise from which heat shield. It would shut up or change if you pushed on the guilty shield.
I misunderstood the A/C use relationship to noise thinking engine was off not just the A/C. A/C is a load the engine deals with perhaps a pulley or the belt itself/tensioner isn't thrilled with and gets over it??
T
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rafale_05
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Aug 23, 2013, 2:16 PM
Post #10 of 12
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Re: Hissing sound from engine bay
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Is this possible even if the sound appears to be coming from the front of the car? I don't know much about heat shields or where they are located on this particular car.
On a related note, the last work I had done on my car was welding the mid-pipes to fix an exhaust leak, and the mechanic might have had to remove the heat shield for this. Not sure what he did exactly, though.
(This post was edited by rafale_05 on Aug 23, 2013, 2:17 PM)
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rafale_05
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Aug 23, 2013, 3:49 PM
Post #11 of 12
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Re: Hissing sound from engine bay
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Alright guys, it looks like the AC has absolutely nothing to do with this.
I started hearing the noise again after about 30 minutes of driving, and this time I managed to record it with a better phone. Please turn your volume up and listen for a sound when I let go of the throttle: http://picosong.com/yq3t/. It seems to be the loudest after the third and last rev in the recording.
I really hope you guys can hear it...
(This post was edited by rafale_05 on Aug 23, 2013, 3:50 PM)
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rafale_05
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Aug 25, 2013, 6:36 PM
Post #12 of 12
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Re: Hissing sound from engine bay
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Sorry for the triple post guys, but I finally figured out the location of the noise. It's coming from somewhere behind the driver side (north american) front wheel. I had the car in neutral with the parking brake on and used a stick to keep the engine revving at 3k RPM.
One of my first thoughts was that this noise could be an exhaust leak maybe in the flex section... but can an exhaust leak like this remain silent until after 20-30 minutes of driving?
(This post was edited by rafale_05 on Aug 25, 2013, 6:39 PM)
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