Air Hissing sound with A/C on, under boost

[chaoscreature]

I have had this issue for a while now, but can't figure out what's going on. I sometimes get a sound that is a bit like a snake hiss, but more... warbly? I have tried capturing it on video but the audio on my i-phone is no good so it wouldn't do any good.

The sound is most prominent with the Air Conditioner turned on. It occurs in every gear, but only when the car is accelerating or under boost. With the A/C off I don't get the sound very often, but sometimes I can hear it on hot days...

I have checked all of the turbo ducting lines and I can't see any signs of leakage on them, and the fact that it seems to be A/C related has me a bit stumped.


Any thoughts?

 

[dmanb2b]

Stumped as well, but check your freon level. I had a freon leak in a non-vw and everytime I turned the a/c on I would get the hissing sound you are describing. That fact that our compressor is constantly spinning may be reason you are still hearing with AC off?? Anyhow, just taking a stab in the dark for ya.

 

[chaoscreature]

Could the expansion valve in the Air Conditioner make this kind of noise?
Would it be possible for this to make noise when the A/C is off?

 

[Luv My 02 TDI]

It only happens when the AC is on? I had a similar noise on my VW beetle when the hose to the inter-cooler was hit by a chunk of road debris hit at hose connection and under pressure (Load) it would leak. Sounded like a air compressor venting.

 

[manny_c44]

Is the sound constant? If it is infrequent is it accompanied by any solenoid 'click' sounds?

 

[chaoscreature]

The only time I seem to notice the sound is when the A/C is on, and the music is off. It's definitely not an every day noise.
I did an oil change today and all the intercooler hoses were nice and tight, at least all the ones I could touch were. There was a little bit of oil seepage at the passenger side hose coming out of the intercooler and I cleaned maybe a teaspoon of oil out of that hose.

 

[chaoscreature]

I wanted to post an update. The temperatures dropped in San Diego and the noise went away until today. It was 90 degrees today at my work. I took the car out for lunch and the noise was back, but without the air conditioner on. I think the noise is just related to very high ambient temperatures and not necessarily linked to the AC.

 

[Bob V]

Same problem here with 2014 Jetta.

Any suggestions?

Thanks

 

[Bob V]

Put car in the air and pulled belly pan. Inspected all intake and turbo plumbing. Tightened the worm drive clamps. Did not fix it. Car still hisses under throttle load when driving. Cannot hear it sitting and revving engine.
Ideas?

 

[chaoscreature]

If it makes you feel better I'm still in the same boat. I really need to make an adapter so u can pressurize the turbo piping and do a proper boost leak test.
Please write if you find something! I'll do the same.

 

[buyingconstant7]

Damnit man, now that you've posted this, I listened for my 2013 doing the hissing, and guess what?! I hear it.

Same exact symptoms and causes. A/C on, under throttle, there is a hissing noise similar to a boost leak(but it's not). A/C blows ice cold and there is no other issues, so I'm going to say it's normal.

 

[mcfisticuffs]

Maybe it's the extra power being applied to the compressor forcing a high-pressure to low-pressure internal system vent within the AC system?

I made that up, but...

 

[lemcc]

Not to bring a thread back from the dead, but I've got the same exact thing. I can't quite put my finger on what it is.

It's only when ambient temps are warm and under load. No noise while cruising. When it's under 75 it's fine. Has anyone found the cause?

 

[buyingconstant7]

I think we can call this normal operation. I don’t have my 2013 anymore but it only had 20,000miles on it at the time and it was exhibiting these symptoms. Wouldn’t worry about it. I now have a 2014 Touareg tdi and it does a similar thing just less noticeable

 

[Nevada_TDI]

I want to throw this out there, a while, back under boost I heard a hissing type sound it happened that one of the bolts in the intake manifold had loosened a little bit. Apparently the slightly loose bolt in the boost made that metal gasket like a reed in the wind instrument.

 

[lemcc]

Interesting. Plausible. It's kind of strange because when I hear it it sounds like it's coming from the driver side footwell. I suppose anything that expands a little and vibrates could be the culprit.

I did notice a few years back that the bolt holding the intake pipe on the turbo was loose. Found that strange.