# P0455 Large EVAP Leak



## VisionQuest78 (Oct 1, 2009)

99 1.8T Passat AEB
Been getting this code for awhile now, P0455 Large EVAP Leak. I ran the basic settings test on measuring block 071. I could hear the LDP cycling and the purge valve was clicking away. The error code in the test says Large leak and the test states system not ok. The only other thing that MIGHT be relevant... during the test it switches between reed open and reed closed. But when im just taking measuring block info it stays at reed closed. Should it be switching back and forth as the valve opens and closes during normal operation? Any help with further diagnostics would be great!
I changed the gas cap less than a week ago, thinking this might be the cause. I smell a gassy/exhaust smell at start up and sometimes during driving. Fuel filter was replaced recently, but EVAP codes were present before this. Im pretty sure that there are no leaks from that. And this last time a few miles before the CEL came on the car was kind of stuttering and almost fealt like it was misfiring. But no misfires, only DTC was the ever present (as of late) P0455.


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## vwemporium (May 27, 2002)

*Re: P0455 Large EVAP Leak (VisionQuest78)*

I have a Vision oh great 071-070 tests.
You could have rodent damage.
On top of the tank.
Easy to isolate with vise grips and a vacuum pump.
Sometimes a can of smoke from radio shack.
Pinch off lines coming out of LDP pump and run test each time to isolate.








Oh and please post an auto-scan it may help.
Best,
Jack



_Modified by vwemporium at 11:40 AM 10-28-2009_


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## VisionQuest78 (Oct 1, 2009)

Ill have to wait until (if it ever) stops raining today before i get out there. But do you care to elaborate a little more? I need to get my hands on a repair manual so i can get a better understanding of how the EVAP system is laid out. But, clamp off each hose one by one and run the test again... whenever the system passes the test that means that whatever is leaky/faulty will be on that line? Is that correct? And then if there are multiple possibilities on that line i apply the clamp just before each of them to isolate it even further?
Also,is there a link to how to do the smoke test with a can of smoke from radio shack? I just recently heard about this, but i dont really know what is involved. Didnt even know you could buy smoke at radio shack, even though they do blow enough of it on occasion! haha


_Modified by VisionQuest78 at 9:21 AM 10-28-2009_


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## vwemporium (May 27, 2002)

*Re: (VisionQuest78)*

No, its time for you to get the manual read then get back to us if you didnt understand what I wrote.


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## VisionQuest78 (Oct 1, 2009)

*Re: (vwemporium)*

I plan on it. but in the mean time a little clarification is all i really needed. If you dont want to, hopefully somebody else will.


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## vwemporium (May 27, 2002)

*Re: (VisionQuest78)*

Not that I don't want to.
I want you understand the system better to help you.
As for the lines, one by one crimp off and run the test 071 to isolate.
No substitution for common sense with a visual inspection of all lines
and top of tank.
Best,
Jack


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## VisionQuest78 (Oct 1, 2009)

*Re: (vwemporium)*

I appreciate the help. I understand the part about crimping the lines...you said the same thing i did in my post above... crimp off each line one by one and run the test. But then, i guess the results is what i need clarification on. I crimp off the line, i run the test...and the system still fails the test? That means that the leak or fault isnt on that line and i need to move on to the next line? Or that means thats the line the problem is on?
What makes sense in my head is that if crimping off that line makes the system pass the test, then that means that is the line with the problem. If the LDP can maintain vacuum in the system with the that line closed off (when it couldnt before the line was crimped) then that means thats the line with the opening causing the system test to fail. Right? Thats what i said above. Am i wrong?
The Haynes manual is the best i can do for now. I know its nothing compared to the Bentley, but i cant afford that now and i dont want to wait for it to arrive in the mail.


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## vwemporium (May 27, 2002)

*Re: (VisionQuest78)*

You are correct sir.
Now go isolate.
Oh and when you pass and find the line, don't leave a crimp in because it will cause other problems that are much more money.
Fix it.
Best,
Jack


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## VisionQuest78 (Oct 1, 2009)

*Re: (vwemporium)*

haha, thanks Jack.
I thought i had an understanding of the procedure...i guess i just had to word it better.
Im going to go pick up that haynes manual now and then hope that it clears up enough to get some work done outside. Thanks again. I will report back when i have some new info.
Just for clarifications sake...does the reed remaining closed except during the test mean anything? Seems like it should open and close during normal idle, shouldnt it? It does during the test, but thats it, as far as i could tell. Maybe i didnt watch it long enough in the measuring block...


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## vwemporium (May 27, 2002)

*Re: (VisionQuest78)*

RTFB buddy. Read the factory book








Robert Bentley is recommended.


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## VisionQuest78 (Oct 1, 2009)

*Re: (vwemporium)*

Ok, so i managed to isolate the leak down to a much smaller area, but i ran out of time tonight to totally track it down. But i want to see what everyone thinks. I started from the LDP and plugged hoses and lines one by one and ran the EVAP system test with VAG-COM. I just went section by section. I got all the way up to the gas tank and then switched to the front of the car and worked my way back to the gas tank. So i have it isolated between the main vapor line the exits the evap canister and the gas tank. And im pretty sure there isnt any rodent damage on top of the tank, i saw no evidence at all of anything making a home up there. So im pretty sure that that is one of three hoses/lines. Its either the main evap line from the evap canister....








Or its the U shaped hose that runs above and over the filler neck. There is also a smaller hose that i couldnt get a picture of that runs from right behind this U shaped hose (right behind the filler neck) and it connects lower down on the neck again not too far above the actual tank...








Or there is a hose that runs over the top of the tank and between the bottom of the car. I assume this is the area that i hear about being a common spot for rodent damage. If this hose is damaged im not sure how to get to it? Does the tank have to be lowered???....








A few of these spots i can just disconnect the hose and plug it and run the evap test again and see if i get a pass or a fail. But if it comes down to being the tank or the hose on top of the tank im not sure what to do really to figure out the problem? Im praying its one of the easy hoses or the hard line from the canister! If i have to lower the tank and/or replace it...im not psyched about that obviously.
Does any one have someinput or suggestions from here???
























_Modified by VisionQuest78 at 7:14 PM 10-29-2009_


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## vwemporium (May 27, 2002)

*Re: (VisionQuest78)*

Ok Nice pics
Now drop the tank slightly to inspect for damaged lines or rodent damage where you cant see. Don't take out just lower on support to inspect.
Take a mighty vac to every section of line capping off at the other side to verify there is no leak.
If the tank has a screw hole in it or damage it can be repaired with a plastic welder, which is a glorified soldering iron. So hope its the tank.
Easy repair, if the lines are damaged. This is also easy to make or get from dealer.
It is very rare that a LDP fails but again most repairs can be done also with a plastic welder.
I have only seen one LDP fail ever due to a faulty installed fuel sending unit o-ring. A stupid person inducing problems making the pump try to pump a tank forever, with a MIL for 2 years.
I have seen loose connections so verify all connections and add a little grease to help the o-rings seal tight.
Again use the 071 test to assist if you are in the right area.
Best,
Jack


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## VisionQuest78 (Oct 1, 2009)

*Re: (vwemporium)*

Thanks Jack,
Im about 99% positive its the tank, or the lines/hoses that run above the tank that arent easily seen. After posting the pics above i went out the next day and checked the rest of the lines and hoses i could get to, and everything seemed fine.
I do have a couple questions about a areas that i came across and i havent been able to find any info. Right next to the filler neck (to the right, with the white zip tie holding it in place) there is a valve (i think?)...i have no idea what it is though? Could this be a possible source of the leak? Heres a pick...








And then there was this white plastic connection. It had a spring inside and was basically just a push connection. The smaller black hose that runs of a 90 degree out of the picture frame also had a push connection on it, and it seemed to plug into another valve but i couldnt get a good pick. These both are right behind the filler neck to and the only way they were really visible was with the fuel door removed and with your face right up to the whole...its way back there. But again i cant find any info on what they are? The lines going into these valves and plastic parts are in good shape, but i have no idea on the valves themselves.








I am confident the LDP is fine and working as it suppose to, and i am also confident in all of the connections in the whole system at this point, except for what is above the fuel tank and between the floor board.


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## vwemporium (May 27, 2002)

*Re: (VisionQuest78)*

Yeah don't think this is your issue.
You would hear it leaking in a location like that when running the test for sure.
Spray glass cleaner all over and run 071 use the foam suds to find, since its pumping and not sucking the tank area.
Best,
Jack


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## VisionQuest78 (Oct 1, 2009)

*Re: (vwemporium)*

so it was infact that valve that is the last picture in my above post. The white part you see is snapped clean off the end of the valve...and its DEFINITELY not supposed to seperate. For those who may want to know, its called a bleeder valve and the part number is 4B0 201 736 A. I managed to get the old one out and new one back in with out dropping the tank, but it was an absolute nightmare! Took some pretty creative thinking. It would have definitely been much easier to just drop the tank.
But no more CEL and no more large EVAP leak!


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## vwemporium (May 27, 2002)

*Re: (VisionQuest78)*

How did that break?
Was the car in accident?


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## VisionQuest78 (Oct 1, 2009)

the girl i bought this from had backed into/through/over a railroad tie or rail road tie embankment, and it was in that rear corner of the car. So that was my guess. The fact that it started as a small leak and then eventually turned into a large...i just assume that it was cracked and then progressively got worse.


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## sciroccodriver (Jan 18, 2004)

I'm about to have to locate the same type of issue in my '01 A4. Not looking forward to it.


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## VisionQuest78 (Oct 1, 2009)

*Re: (sciroccodriver)*

well, using VAG-COM and running the EVAP system test repeatedly, while plugging lines one by one and step by step wasnt bad. I am SOOOO glad i purchased the VAG-COM software, i cant imagine owning this car without it! But me and friend spent hours trying to track down this leak. But we were both going into it as totally NOOBS too. Spent quite a bit of time finding things, and tracing lines and figuring out how the system worked. If you're starting off with more knowledge than that it wont be too bad for you hopefully. Having done it once and finally succeeding in fixing it, i could do it again in a third of the time atleast. but good luck!!!


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## Uwe (Jan 16, 2000)

*Re: (VisionQuest78)*


_Quote »_ Having done it once and finally succeeding in fixing it, i could do it again in a third of the time atleast.

This is typical of almost anything you do on a car. In the late 1970's I remember replacing the water pump on my first car twice in one day because the "new" pump leaked worse than the one I took out. Doing it the second time went just about 3 times as fast as doing it the first time because I now knew exactly what to do. 
-Uwe-


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## sciroccodriver (Jan 18, 2004)

I gave up and took my car to Absolute in Durham NC. Evan hooked up the smoke machine and found the leak in about 30 seconds. Months ago I installed an exhaust and the clamp closest to the muffler and spare tire well rubbed a hole in the plastic hose that goes from the LDP to the Evap can. Quick fix and my problem is gone. Thanks for this thread.


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