# hissing sound.....air leak?



## edeher721 (Aug 20, 2012)

i have a hissing sound coming from the passenger side of the engine. when i get close to it it sounds like its coming from this hose going between the intake manifold and the oil valve thing, lol, for lack of a better term. here are two pics to help my explanation. is this a likely vacuum leak?


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## Holmes741 (Feb 13, 2012)

I'll check tomorrow in the Bentley for ya, I've heard the European boras don't have that connection so now I'm curious


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## edeher721 (Aug 20, 2012)

thanks bro some one sent me some pictures on his catch can set up but it looked totally different to me.


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## Holmes741 (Feb 13, 2012)

Bentley doesn't even mention it, and I was looking at it on my car and I can't explain why it's even there. But, if its not sealing properly, then air will get around it, which s never good.


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## gti_sean (Feb 14, 2009)

I was the one who sent the pics to you edeher721. It is the same, the hose he is pointing at is referred to a service port from what ive heard, though i dont think anyone has ever used it... its a dead end to an opening on the intake manifold, a 1" rubber plug on the manifold does the trick

heres a pic...


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## JDM_LOL (May 24, 2012)

do you have a rough idle? My car has had a crappy idle for a while, ive noticed the hissing sound myself, and just recently it got audibly noticable with the hood closed, and if i lightly hit the accelerator to bump the throttle up to about 1200 rpms it makes all kinds of ugly noises and kind of sputters... I took propane to it to find the leak, and found that my leak was actually closer to where it connects to the pcv valve (same hoses) about 3-4 (almost directly behind and below the throttle body) inches from the pcv valve there is a teeny tiny 1/8th inch hose wrapped in some kind of insulator, well mine is broken in two, I have no idea what its called and will have to do some research on alldata tomorrow to find out wtf it is...


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## MKIVRider (Feb 20, 2008)

JDM_LOL said:


> do you have a rough idle? My car has had a crappy idle for a while, ive noticed the hissing sound myself, and just recently it got audibly noticable with the hood closed, and if i lightly hit the accelerator to bump the throttle up to about 1200 rpms it makes all kinds of ugly noises and kind of sputters... I took propane to it to find the leak, and found that my leak was actually closer to where it connects to the pcv valve (same hoses) about 3-4 (almost directly behind and below the throttle body) inches from the pcv valve there is a teeny tiny 1/8th inch hose wrapped in some kind of insulator, well mine is broken in two, I have no idea what its called and will have to do some research on alldata tomorrow to find out wtf it is...


I believe the hose you are talking about is the small hose that goes from the intake manifold to the evap purge line. Mine was gone when I bought my car used. Used some clear hard plastic tubing to fix it. #17 in the diagram


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## JDM_LOL (May 24, 2012)

ah yes, that would be it... wow an evap line being broken and I have no CEL, crazy...


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## BoraNewbie (Jun 3, 2014)

*Similar problem*

My 2003 Bora (Jetta) 2.8 v6 4motion started making this hissing sound yesterday whenever you tap the accelerator lightly. I suspect it's the same sort of problem, since an exhaust leak would likely be more noisy than this, but don't know how to locate a possible air/vacuum leak.
I realise this is an old thread, but I didn't want to start a new thread to ask something that's been discussed here before.
I made a video showing the hiss it makes to make it easier for everyone to understand what sort of sound I'm talking about.
Any help will be much appreciateed!

https://www.youtube.com/watch?v=TIicJYBYvyc&feature=youtu.be

Thanks

Mark


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