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gomi_otaku, VW Technician
Category: VW
Satisfied Customers: 3352
Experience:  VW FastTrack '00-'01, VW Academy Chicago and Seattle '00-present, VW Certified
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I have VW Jetta with PO442 (evap system small leak). Ive been

Customer Question

I have VW Jetta with PO442 (evap system small leak). I've been to VW dealership 5 times so far. They have replaced LDP, gas cap, then checked if my software was up to date - it was. Next step they gonna take is take the whole gas tank apart and look for the problem there. I have a feeling that the problem is not even there. I keep throwing in money and get no results (this "next step" is gonna cost me $450 plus whatever they decide to "fix" when they open the tank).

Do I have any alternatives? I need that engine light to go away, but I can't just keep paying them for their fruitless investigations.
Submitted: 7 years ago.
Category: VW
Expert:  JamesH replied 7 years ago.
Can I get the year of your vw jetta
Customer: replied 7 years ago.
Expert:  dan replied 7 years ago.
An easy thing to check is the seal for the fuel pump and sending unit. Pull up the back seat on the passenger side and underneath a piece of carpet is a cover with three phillip head bolts holding it down. Remove this cover and check for any evidence of mouse chewings such as insulation or sunflower seeds sitting ontop of the gas tank.
Customer: replied 7 years ago.
So, I took it to VW, they checked the whole area and said there were no holes or anything of that nature. They said, there are a few valves inside of the tank that they can not check, and they assume that they are the problem (since they checked everything else). They want to change the whole fuel tank.
I don't know how much is it gonna be, but I know it's expensive. Do i have to do this? Again, what are my alternatives?
Customer: replied 7 years ago.
Relist: No answer yet.
Expert:  gomi_otaku replied 7 years ago.

Any good shop should have a "smoke machine" that uses nitrogen and a special fluid to create a fogging smoke inside the tanks and fuel system. They should either be able to detect if there are external leaks with this, or they can simply use the pressure test function of this machine to detect how much pressure drop there is- then spend some time pinching off lines until they figure out where EXACTLY the problem is, instead of just guessing. There are a number of hoses outside the tank. There are no hoses "inside the tank" that can register a leak- the tank is pressurized, and the test involves timing to see how long it holds pressure before the LDP needs to pump again. If it leaks internally in the tank, it's not LOSING pressure!!

Some common areas of leaks are the rubber seal for the fuel pump, the N80 purge valve sometimes gets carbon dust in it and doesn't seal exactly right, and sometimes the rollover valve gets a small leak past the diaphragm (which isn't typically available separate from the tank)