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New to the forum and it has been very helpful to search in the last couple days.

I've been troubleshooting a CEL on my wife's 04 v8 Treg for a couple of weeks and and a bit over $1k so far. She got the loose gascap message followed by CEL and took it to the shop while I was out of the country. After they replaced a lot of the EVAP stuff under the hood (and the gas cap) they appeared a bit stumped. I called and asked them to smoke it -- they say a small amount comes out over the gas tank. I asked them to stop replacing stuff and when I got home I borrowed a Vag-com which shows a large EVAP leak which returns after a try of clearing the code.

I'm guessing that it is either the black fuel tank breather line (possibly from rodents) or less likely the fuel pump seal if the shop was right about the smoke.

My question for the more experienced here is: can I get at the breather line from the access cover under the back seat or do I have to drop the fuel tank which would probably be a full weekend deal?
 

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Did you get any resolution on this?

I've just started getting this problem intermittently as well. The DTC is p0455 for a large evap leak. Does anyone else have any experience with an evap leak? I have an 05 V8 btw. I imagine this Treg is not currently a Low Emission Vehicle ;-).
 

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nope woody, never did get any help. Pulled fuel pump covers under back seat (need 10mm trisquare) fuel pump gaskets OK. Finally had shop drop the tank. Small smoke from where the various other lines enter tank. Lines themselves OK. Solution would be to replace entire tank. I decided to forget it and drive with the MIL. Down much $$$ for the diagnosis without any treatment and lots of new parts I didn't need.
 

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That sucks to have no resolution after some pricey repairs. I'm sure replacing the tank would not be cheap either.

I'll check those pump seals and poke around under the good a bit; maybe something obvious will jump out at me.

I have noticed that when I'm refueling, the gas pump cuts off as if the tank is full even when it is almost empty unless I squeeze the handle on the pump VERY lightly. Maybe that has something to do with it.
 

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check the vent line that opens near the cap. Here's some of what I found searching this problem some months ago:

Here's a link to some helpful diagrams:
http://users.erols.com/true2scale/evap01.jpg

Fuel tank,fuel filler and attachments, 1 - Sealing cap
2 - Seal
3 - Securing bolt
4 - Tank flap unit
5 - Breather line - Black
6 - Ground connection
7 - Breather line - White
8 - Gravity valve
9 - Seal
10 - Changeover valve
11 - Breather line - Black
12 - Pressure retention valve
13 - Breather line - Black
14 - Fuel tank
15 - Clamping washer
16 - Heat shield For fuel tank
17 - 25 Nm
18 - Clamping nut, 2 Nm
19 - Fuel tank cover
20 - Securing strap
21 - Supply line - Black
22 - Fuel filter
23 - Screwtype clip
24 - Breather line - White
25 - Seal
26 - Fuel delivery unit
27 - Union nut, 75Nm
28 - Supply line - Black
29 - Return line - Blue or with blue marking
30 - Connector
31 - 10 Nm
http://users.erols.com/true2scale/evap02.jpg
1 - Breather line - White
2 - Seal
3 - Breather line - Black
4 - Junction piece
5 - Connector - Black,3-pin
6 - Vacuum line - To intake manifold
7 - Leak Detection Pump (LDP)
8 - Connecting hose
9 - 3 Nm
10 - Air filter for LDP
11 - Connecting hose
12 - Bracket
13 - 10 Nm
14 - EVAP canister
http://users.erols.com/true2scale/evap03.jpg

EVAP canister system, assembly overview 1 - Tank flap unit
2 - Fuel tank
3 - Fuel delivery unit
4 - Intake manifold
5 - Fuel pressure regulator
6 - Fuel rail with injectors
7 - Fuel filter
8 - EVAP canister purge regulator valve -
9 - Test union
10 - Gravity valve
11 - Pressure retention valve
12 - Changeover valve
13 - EVAP canister-In rear right wheel housing, behind wheel housing liner
14 - Leak Detection Pump (LDP) -
15 - Air filter for LDP
 

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Thanks for sharing! Beautiful pictures!!
Now I can start the hunt for my rough idle , and hesitation problems that started just a few weeks after I bought this 3,2 V6 petrol Touareg.

The dealership gave me the diagnostic that the timing chain was too long and that I just had to spend 10500 USD to have them drop the engine and change the chain..
I adopted to buy a low milage engine from a same YM Touareg that had an accident to the rear end.

After swapping engines the problem with intermittent rough idle where the engine eventually stops and hesitation on acceleration is still there...

This car has turned a nightmare and already cost a fortune but I am determined to beat the VW gost...Any good ideas very much apreciated..
 

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Hmm

I also have problem with tank breathing.

DTC: 16825-P0441 EVAP emission control sys incorrect flow.

Haven´t found out whats the problem yet. Only know after crawlig around that I don´t
have a "leak detection pump" or a " Purge Solenoid Valve (N115)".

So its probably the canister itself or some of the vacum lines. And there are alot of lines down there.
 

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Got a code that tells me it's one of my vents, and that also happens to me, where at about 40 litres into my fill up I here some crazy venting coming directly from the tank, and then pop the fuel nozzle shuts off. I wait about 4-5 seconds until the venting ceases, and begin refuelling. It does not repeat itself. My concern now though is about those vent lines? I've been told that it if spurts out t you while your refuelling its the one on top of your tank that doesn't work, (which makes sense because you've got an accumulated pressure n the tank.)And if that's not the case then probably the one in the engine bay. Iunno anyone got any suggestions? Either way it's not a big problem i believe but I would like to get it solved. Plus btw good job on the diagrams, helpful stuff that is.
 

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I hate the idea of just "throwing parts at it" but I fear that is what the dealer will do at considerably more expense. Should I just go ahead and replace the leak detection pump. Would a bad pump trigger the P0455 (large evap leak).

Between this and the current issue I am having with bearing and / or tire noise, I am seriously contemplating if it is the end of the road for my 2004 Treg. I suppose there is a reason we do not see too many left on the road.
 
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