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I have what I'm assuming is a leak either in the EGR or VNT system, but I'm trying to narrow it down a little before I go pulling stuff off or order parts. The problem occurs as follows...

1) when increasing the throttle and just before boost (say <2,000 rpms), there is a very loud hissing noise. once boost is achieved, the noise seems to disappear, and I don't think it's that it is overcome by the noise of the turbo and engine because I recreate it all the time and listen carefully. Also, it doesn't seem to affect power once the turbo has spooled.

2) when at cruising loads, say 50mph in 5th gear.

3) sometimes at idle. say I'm at idle and it is not happening, all of a sudden, it sounds like something just opens up and starts hissing.

I'm thinking because of the occurrence at idle, that it's the EGR because why would the VNT actuator move at all at idle. But because of how it happens when building boost and then disappears, it makes me think it could be a leak around the actuator arm.

I've tried looking around the area for soot and stuck my head under the hood when it was happening at idle, but I can't seem to identify the source, especially since it's so tight between the motor and the firewall. And I don't have access to a VCDS. Also, it seems that it's affected fuel efficiency. It started at about 40k miles and we now have 113k, and the noise hasn't gotten worse, but fuel efficiency seems to have fallen, and we haven't changed the station we use to fill up. :edit: And I'm super anal about maintenance, so I doubt it's related to something like a clogged fuel filter.

Any advice is appreciated.
 

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1 Are you sure it's not the sound of the turbo? Take a look at the FAQ for how to do a pressure boost leak. That will rule out any intake leaking.

Looking for soot will definitely show any exhaust leak close to engine.

Maye exhaust pipe leak?
 

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Chitty, I'm certain it's not the turbo...I've been around enough boosted cars to know what normal sounds vs. leaks are. I just hate the diagnosing part. Also, the occurrence at idle kinda rules out the turbo. And the varying nature of the leak with load and building boost really makes me think it's related to either the VNT or EGR, because those are the only two things that would vary with load and boost.

I plan on trying to do a more thorough inspection this weekend from under the car. Like I said, I was trying to rule out as much as possible before I pull anything so I can hopefully order the right gasket set for the job.

Questions: Where the actuator arm enters the turbo to vary the vanes, is there just an o-ring to seal it? Also, is the EGR prone to a leak at a specific gasket?
 

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There is no o-ring. There is a bronze bushing, see the VNT inspection and adjustment article for pics. The most likely place for the EGR to leak is at the joints from the exhasut manifold to the valve. Look for soot stains.
 

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I have exactly the same problem in my 2004 2.0TDI BKD DSG Touran.

After each gear change from ~1500 to 2000 RPM I hear this hissing/bird singing noise, and when the turbo boost is achieved, I only hear the normal sweet TDI whisteling sound.

I am not sure if is a bit slow until turbo boost.

I am very interested in hearing if anyone has a goiod explanation.
 

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Perhaps your car has an intake resonance somehow or some clamp is loose? This makes the air vibrate like blowing across the top of a bottle.
 

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I managed to take a picture behind the motor, I believe it is soot on the EGR pipe? Can you confirm, that this is my problem, and where does it seem broken??



My engine is a 2.0 BKD 140 - does anyone know where to buy a new pipe (and/or part number), if you think that it is the cause ?

Thanks for your help.
 

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Yep, 100% sure exhaust leak, the soot is your proof. Could be at the gaskets or the piping. It's hard to see where it's coming from but you could probably see better in person.
 

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Thanks again for your information, so it seems to be a typical leak. Great. I will see if I can get it more detailed, where the soot is coming from.

Do any of you know where to buy spare parts, and is it possible for me to change it myself, done a bit of work in the engine compartment, but not much space behind the engine of a Touran.
 

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My 06 Jetta is also making that same hissing noise. There appears to be an exhaust leak coming from the EGR cooler. The actuator and linkage on the EGR cooler are covered with soot. Have cooler, gaskets, and heater hoses ordered. While its in pieces I plan to clean the intake so there is an intake gasket coming too.
 

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I found some info on the parts, but there is not much space for me to do the exchange:




I found these numbers in a German forum, with prices:

2.0 TDI Motor BKD (140 HK):

EGR pipe: 03G 131 521 T 64,68€ netto

Gasket 1: 038 131 547 A 2,53€ netto

Gasket 2: 069 131 547 D 2,09€ netto

N 904 154 05 0,86€ netto

N 908 946 01 0,48€ netto



 
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