Are there any common leak points that cause exhaust fumes to enter the cabin through the hvac?

[needsmoarturbo]

I have a fairly new to me 2011 JSW and any time I come to a stop with the hvac fan on it quickly starts smelling like diesel exhaust fumes in the cabin.
While moving/driving no problems with fumes.
It did have some accident damage when I got it so maybe something cold have got knocked loose underneath. I haven't really been under it yet.
I realize I will have to go underneath and look, but I'm just trying to see if there are any likely suspect area to concentrate on. Searching the forum didn't generate many leads for common leaks.

When outside the car there dont seem to be any fumes, but its been breezy lately so maybe it just gets blown away.. same with the hood open I cant really smell anything under the hood. It does sound like perhaps the rear right hand side of the engine is loudest from below and above but that may be normal, this is my first TDI car so I dont have much experience here.
I am no stranger to audi/vw or mechanical work though, so I can probably figure it out with a little guidance.
Thanks for any ideas.

 

[oilhammer]

My guess is the V-band clamp gaskets, one of them is not seated. Lots of these cars got really, REALLY, awful workmanship at the dealerships during the "fix" and all sorts of things were left loose.

Clamp #1: at the turbo outlet to the DPF, under the hood up high, back by the firewall, right next to the oxygen sensor.

Clamp #2: down low under car, right behind subframe below the firewall area, after flex section of downpipe/DPF assembly.

Clamp #3/4: on either side of the exhaust flap, in the exhaust pipe in the middle of the car (the part with the servo made on the side of it)

Other clamp: on the EGR filter pipe, this is a miniature version of the above clamps... it is located middle of the downpipe, near the right inner CV joint area, that goes to the low pressure EGR valve/cooler assembly on the back of the engine. The other end of this short pipe it held to the cooler with a two bolt flange with a gasket.

If you smell exhaust, chances are it is leaking pre-DPF, which means clamp #1.

 

[needsmoarturbo]

Oilhammer---Excellent recommendations. Thank You! I'm going to try to get it on the ramps after work today and take a look.

I'm trying to get my wife to let us take this on an upcoming road trip but its not gonna fly if every time we stop we get fumes. It does seem to help if I keep the fan on recirc, but I need to find a permanent solution to what I suspect is the real problem.

 

[needsmoarturbo]

Well, I did some investigating last night, I pressurized the exhaust by putting my shop vac exhaust and some rags into the tailpipe openings and feeling all around under the car behind the engine and couldn't feel anything. Sprayed soapy water on all the v band joints and the flexpipe and saw no bubbles...

Then I removed the shop vac started the engine and stuck my hand down from above and from below trying to feel for a leak. Had my hand on the #1 clamp mentioned above as much of it as my fingers would fit, but could not find a leak. The only place that "might" have had a slight feeling was in the area right around the turbo, but it was so slight it could have been the breeze blowing up from under the car.... kinda hard to access that area.
Is there a joint between turbo outlet and the clamp#1, or is that clamp right on the turbine housing itself?
The tailpipe smells so clean its definitely not coming from back there its just gotta be a very small leak under the hood somewhere
The search continues....

 

[oilhammer]

The #1 clamp connects directly to the turbo/exhaust manifold casting itself. And as you already surmised, the exhaust (despite the EPA's ramblings) at the tailpipe is VERY clean, so you will not smell that. So if you smell "fumes", it is almost certainly before the DPF, which is the #1 v-band clamp or the turbo itself, or the high pressure EGR port, which is on the "side" end of the turbo casting towards the flywheel end of the engine, connects to a pipe, then goes across the top of the bellhousing area and into the EGR valve itself on the front of the engine. Look for soot marks.

 

[JohnTF]

Decades ago I started using this to look for air-leaks , vacuum-leaks , intake / exhaust leaks ,
a stethoscope , they even sold as mechanics tools - to listen to bearings , they come with a metal rod about 20 inches long - you touch a spinning bearing in question , this allows you to hear a bearing going bad - long before most any other method .

I added to mine by taking off the diaphragm & metal rod , and used a long hose and metal fuelline to listen for air leaks , worked great in engine bays that were crowded with too many vacuum hoses , or stuff in the way to get to with anything but this small tube - connected to my stethoscope .

 

[vdubdiesel]

i have the same issue in my 2011 JSW. Just wanted to thank Oilhammer for the suggestions and ask Needsmoarturbo to keep us updated as to the final fix. I'll be looking at band #1 real closely next chance i get.

 

[needsmoarturbo]

i have the same issue in my 2011 JSW. Just wanted to thank Oilhammer for the suggestions and ask Needsmoarturbo to keep us updated as to the final fix. I'll be looking at band #1 real closely next chance i get.

I've been gone on a trip but when I get back home I'm going to be checking the egr tube and connections and try to check around the turbo again. If I fine anything visual I'll post a photo and I will update

 

[needsmoarturbo]

Well I have tried checking the EGR tube and associated connections, but as you know its pretty hard to see/reach anything in the area without removing at least the intake tubing from the airbox.
I guess thats my next step, take off the intake tube and use a mirror and light to look around because I can't feel or see anything obvious. Might have to remove that piece from the firewall thats below the windshield wiper valence to see anything back by the turbo too theres nothing obvious from below.
I will probably check the torque on band #1 and make sure its not loose just because its accessible and why not.

 

[06bluebeetletdi]

My beetle had an issue with exhaust fumes in the cabin, it was a sensor on the side of the dpf, it was backed out partially. Mileage was less than 40k, emissions modification was at 61k. My air filter was black from soot.

 

[needsmoarturbo]

The thing is it must be a pretty small leak. Some days I seem to notice it right away and some I can't tell it's there or not so I'm not sure if it comes and goes or that has more to do with the breeze that day or if I have a stuffy nose, but from what I understand I shouldn't be smelling anything in the cabin....

 

[needsmoarturbo]

Well after driving the car all summer I thought the issue was gone. I chalked it up to a leak caused when replacing the motor mount previously or something but I didn't notice any smell all summer.

but now that it's cold again I get an occasional whiff again, so I don't know if it's just such a small leak it only open up when it's cold out?

 

[Bacardiac]

Found my leak… Not sure if the egr clogged or bolt fell out.

7AB86CD4-425F-469F-9094-32EF55EA5F67.jpeg

• Bacardiac
• Oct 21, 2021

 

[oilhammer]

The examples of poor workmanship from the Dieselgate "fix" was an almost weekly thing here. Looks like you found one yourself. Usually it is the V-band clamp connections are leaking.