# Large EVAP leak - where is the charcoal canister & LDP?



## twocati (Dec 6, 2009)

*** Please note my car is a USA spec. TT - so the EVAP system is different for example compared to a UK version ***

Folks - I haven't driven my car much since it's last dealer service (2000km) at which point a DSG service and a standard oil change was performed (Early November 2013). The car has been in the garage and I would take it out on occasion however last month the MIL came on and I had a friend scan the error code 0455 Large EVAP leak.

We did a reset and I noticed when I went for a drive the display asking me to tighten the gas cap....It did seem a little loose (subjective) so I bought a new one however the engine check light is still on.

I'm not a fan of have the dealership bill me time while they try to locate the issue so I did some research and found this video quite helpful as now I understand the system components.






Good news is a large evap leak is easier to sectionalize compared to a small one.

I've already determined my N80 Purge Valve ( a likely suspect) is functioning correctly as it's not leaking into the intake manifold. In the other direction it appears to be leaking - I should be able to locate where the issue is with a "smoke machine"  and a flashlight!

I also found a diagram of the fuel tank and connections in the knowledge section however what I cant find online is some diagrams or pictures specific to where the *charcoal canister and LDP* (Leak Detection Pump) are located on a MK II - I would appreciate someone posting some links or pictures where these components are located. This will help me in ensuring I've removed any inner fenderwells/panels so they are visible.

Thanks so much!


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## twocati (Dec 6, 2009)

Ok - I found this diagram and I see the charcoal canister (1) and LDP (5)










Now I'm curious where this component resides - is it above the muffler behind the heat shield? North American cars have a interesting trunk floor that has a raised area where this could reside in..










I'm afraid the shape of the charcoal canister and this "hump" are too similar....fk..they both even have 5 "dimples" on the perimeter...how the F do you get to it? Do you have to remove the rear muffler, then the heat shield?










I'll keep searching for the LDP location...


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## brittan (May 18, 2007)

The diagram you have is probably your best guide to locating the components.

The evap system for UK and Europe cars is very different: the charcoal canister is smaller, square in section and next to the engine. We do not have a LDP. Is it located just inboard of the body mount for the trailing arm for the RH rear wheel?


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## TT-driver (Sep 14, 2010)

twocati said:


> .how the F do you get to it? Do you have to remove the rear muffler, then the heat shield


Looking at the way bolt 2 is drawn, I'd say yes, I'm afraid so.

I'd expect the LDP to be on the left of the car, approximately 40 cm in front of the left rear wheel. So underneath the rear seat, accessible from the outside. You may have to remove some aerodynamic cladding.


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## brittan (May 18, 2007)

I should have checked first:

The LDP is at the top of the rear left wheel arch behind the arch liner.

The charcoal canister is exactly where you suspect it is and you do have to remove the rear section of the exhaust and the heat shield for access.


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## twocati (Dec 6, 2009)

Thank You Brittan and TT Driver!

There are may Audi forums however if you own a TT, this is the absolute best for TT owners!

I will have a look for the LDP - I understand it will be on the opposite side of the filler cap.

I'm not clear if it's in the rear wheel well or under the car - I will have a look and report back.

I want to locate everything before I try to isolate the leak. Hopefully it wont be the Charcoal filter.

Thanks again!!


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## brittan (May 18, 2007)

twocati said:


> I will have a look for the LDP - I understand it will be on the opposite side of the filler cap.


Yes.



twocati said:


> I'm not clear if it's in the rear wheel well or under the car - I will have a look and report back.


It's in the wheel well, directly above the wheel and above the well liner.


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## brittan (May 18, 2007)

A view looking up into the wheel well.


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## twocati (Dec 6, 2009)

Exactly as you stated and in your diagram! Thank You!

#2 is the vacuum line that powers the LDP to create pressure.
#5 is the tube going to the Charcoal canister - there is a similar tube on the filler side....

The LDP seems fine - no internal leaks or hoses damaged around it. I don't have the Ross Tech micro can cable yet ( I will order one) so I was unable to do the recommend diagnostics. I did plug the LDP air intake and gently blew in LDP outlet #5 and there was absolutely NO leak  . LDP is fine.

I elected to remove both inner fender well covers as there is one tube from the LDP and another from the other fenderwell (under the filler cap) going to the charcoal canister....

I disconnected the LDP end and plugged the other end. Clearly there is a leak between the LDP end and the filler cap end on the other side of the car ...sadly I can hear air escaping from the charcoal canister area underneath the car when I gently blow into the tube #5 toward the canister......errrrrr..why does the fault have to be in the most complex area to service????

Now I may be lucky in that I may be able to remove the heat shield as I have an aftermarket cat back exhaust that is a fraction of the size of the OEM unit ...I may be able to remove the heat shield without removing the exhaust and possibly the canister for a detailed inspection....and all connections....

I will keep you posted on progress.

*BTW* - I noticed my cable to the down stream O2 sensor dangling outside of its clip under the car as well as the "connector box" was loose (under the car - near the exhaust tunnel) - it rattled - I tightened the metal clip and re positioned the cable and snugged up the connector box.
Also, on occasion I would hear subtle rubbing while cornering hard on right hand sweepers from the left wheel well - it turns out the inner cover "bubbles" out about 1/2" (the right side was fine and tightly follows the inner profile) in the area I would expect the tire to make contact - I will use some rubber adhesive to tuck this in .


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## TT-driver (Sep 14, 2010)

Good work!


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## brittan (May 18, 2007)

twocati said:


> I disconnected the LDP end and plunged the other end. Clearly there is a leak between the LDP end and the filler cap end on the other side of the car ...sadly I can hear air escaping from the charcoal canister area underneath the car when I gently blow into the tube #5 toward the canister......errrrrr..why does the fault have to be in the most complex area to service????


That's just the Law of Sod in operation.

At least you have found the leak! Hopefully it won't be TOO bad to access for the repair.


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## twocati (Dec 6, 2009)

I'm taking a little break ..after successfully being able to remove the heat shield and leaving the exhaust intact!!!!

I wasn't sure if I was out of the woods yet as I was not sure there was enough clearance to drop the canister and maneuver it out around the exhaust. It took some maneuvering but I got it out!

Pluging the inlets and blowing into on confirmed there was a leak and upon inspection I found a crack.

I called 3 Audi dealers and no one had one in stock - the price varied from $140 to $116...CAN - that said I noticed something interesting in that the canister had 2 part numbers.

One part number next to the VW logo was 1K0 201 797 B and the part number next to the Audi logo was 8J0 201 797 D.

If you google them, they appear to be the same part! I was curious of VW / AUDI the price difference.

Interestingly the VW dealer had the part in stock but it was even more expensive at $188 and could not explain why the VW version was more expensive ...this is consistent with ECS also ..asking $170USD for the VW version...

http://www.ecstuning.com/Volkswagen-Gol ... /ES315708/

Yet the Audi version is can be found online as low as $68USD!

http://www.jimellisaudiparts.com/produc ... 1797D.html

That said I ran out of time during my investigation and the dealers closed so now if order tomorrow it wont arrive until Tuesday (it's a long weekend here in Canada )....and I don't want the car out of commission over the weekend...

I elected to repair the crack with my all time favorite Automotive GOOP!

I cleaned up area with my trusty Dremel tool and applied a liberal amount of GOOP....after 40 minutes a did a quick test and it is SEALED!!!

I will install it and will let it cure overnight.

I will continue to research finding a new canister at a great price and have it handy should I need it.

I'll post a picture of the repair - unfortunately I didn't snap a picture of the crack before I cleaned it up an GOOP'd it .


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## twocati (Dec 6, 2009)

Ok here is the photo:



I have to say I really enjoyed my day working on my car - I call it therapy - so different than what I do for a living :wink:

I was intimidated by the complexity of the EVAP system as was going to take it to the dealer - I'm glad I didn't as this would have been a >$1000 CAD repair for isolating the problem and parts...

I'll put everything back together tonight but wont run the car until tomorrow.

Does anyone know how long it would take for the MIL to clear (if this was the issue) or does this require a reset?


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## TT-driver (Sep 14, 2010)

How on earth can something so well protected break? Does it rub against the bodywork?

Job well done I'd say.

I suppose the fault will clear itself, since the system tests itself. But I don't know how long that will take.


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## twocati (Dec 6, 2009)

> How on earth can something so well protected break? Does it rub against the bodywork?


It is protected....perhaps it was defective from the start and finally cracked right through?

Well I'm very very happy to say that after finally taking the car for a drive, the MIL went off within 20 minutes!!!! NO MIL !!!

Cost to repair $0 thought it did take the better part of the day to sectionalize...

That said I have a more serious issue that didn't create a MIL - cam lobe -I'll start a new thread......


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## brittan (May 18, 2007)

Good work!

Cam lobe: :x


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## robbie_boy (Nov 5, 2010)

twocati said:


> Ok here is the photo:
> 
> 
> 
> ...


I have the same Code being thrown on my 3.2. Mine is only telling me that it is a "very small Leak". I guess I'm going to have to do this same thing in the coming weeks. The only issue I have is that I still have the original exhaust [smiley=bigcry.gif]


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## twocati (Dec 6, 2009)

> I have the same Code being thrown on my 3.2. Mine is only telling me that it is a "very small Leak". I guess I'm going to have to do this same thing in the coming weeks. The only issue I have is that I still have the original exhaust


No doubt the "small" leak is harder to isolate as from what I've read the Leak Detection Pump will alert on holes as small as 0.020" !

I also would not assume your leak is in the canister- please note that USA/Canadian cars are configured as my thread however it seems European cars have a smaller canister that is very easily accessible in the engine compartment.

If you have a Ross Tech cable and VCDS software you can repeatedly run tests while you plug off different sections to isolate where the leak is.

The N80 Purge valve is thought to have a high failure rate (mine was fine) and it is not an expensive swap. Also, try swapping out the gas cap with a friend to see if that's the problem.


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