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Fuel vent DIY for mk4 VW Jetta, New Beetle, Golf, and Passat TDI

Apr 15, 2014 at 10:38 PM
Fuel vent DIY for mk4 VW Jetta, New Beetle, Golf, and Passat TDI
  • Fuel vent FAQ for 1999-2005 VW Jetta/2006 New Beetle/Golf and 2004-2005 Passat, Volkswagen TDI

    difficulty: 1/5

    to see the mk3 TDI vent FAQ, please refer to 1000q: mk3 fuel venting

    Introduction

    All mk3 and mk4 VW TDI used a fuel tank vent in the fuel filler neck to vent air out. Venting is when you press on the vent to release trapped air to add more fuel to the tank, extending your car's range per tank. Look inside the filler neck and you can see a button, see below for detailed pics. Press on it when the tank is almost full and you will hear the hiss of air venting. This lets you add about 2 extra gallons of fuel. Venting does not increase fuel economy at all, it just lets you add a little more fuel to increase miles per tank. You can also remove the vent's spring loaded internals so that you don't have to press on the button making venting faster. This is shown in this article. This does not apply to mk5 cars (2005.5+ Jetta).

    Warning: Do not do it on a gasoline car. Gasoline vapors are flammable and should not be released to the atmosphere. A gasoline fuel tank is connected to the engine emissions system and they burn these vapors. Removing the vent or otherwise altering the fuel filler neck could cause a fire hazard!

    The TDI vent only connects the filler neck and the fuel tank. It's not connected to anything else like an emissions system. This is because diesel is a heavier fuel than gasoline and the vapors are not flammable at room temperature and pressure. This procedure doesn't release any extra diesel vapors and later Jetta/Golf TDI fuel tanks are vented to the atmosphere anyways. Venting also works on b2 passat and a2 jetta diesel but those are pre-TDI and outside the scope of this article. The vent is normally opened with you put the fuel cap back on.

    The only problem venting could cause is if you were to fill the tank all the way up to the very top of the filler neck and then park the car in the heat. Heated diesel expands much less than gasoline so the likelihood of overflowing fuel is very low but spilled diesel can melt asphalt and should be immediately cleaned up. Vent at your own risk! If you vented all the way, just drive a little bit to lower the fuel level and you should not have any problem with fuel spills. Disclaimer: As with any other information on this website, it is done at your own risk! This website is not responsible for damage to your driveway, any persons and/or property resulting from any tips you found here!

    Truck high flow fuel pumps are larger and can cause foaming if you fill at their max speed. The high flow large pumps will not fit all the way into the mk5 filler neck due to a blocking rib. The mk5 cars don't use this vent anyways.
    Do not attempt this on a gasoline car because it is part of their emissions system, gasoline evaporates much more, and it can create a fire hazard. The air space may also help prevent fuel spills in a crash when the tank is full, especially important with a gas car since gas is more volatile than diesel. The gasoline vapors are normally trapped and burned in a gas car and the vent helps route vented gas back to the fuel nozzle instead of into the atmosphere. The TDI does not use a "carbon canister" or "evaporative emissions" system.

    While you are working on the fuel door, here is another mod to make it pop open much further when you press the release button: 1000q: fuel door spring open wider mod

    Procedure for mk4 Jetta, Golf, New Beetle, and Passat TDI
    - additional notes for New Beetle below

    Here is a video with the fuel tank removed for illustration. Not shown is backflushing the vent of any dirt before putting the vent body back. Below are detailed instructions.



    Open the fuel filler door and remove the T-20 torx bolt by the filler door lock. Remove the filler cap and stuff a clean paper towel down the fuel filler to avoid getting dirt inside.
    [​IMG]

    Pivot the rubber surround boot out and to the right. As you pull it out you will have to pull the entire assembly to the left. The fuel filler door comes out with it. Set aside to get more room. The latch strike can also be pulled off. Pinch the sides and slide it off the latch solenoid button.
    [​IMG]

    There is a small tab on the rear of the vent body, push up on it (white arrow) while pushing the vent button towards the rear of the car (the direction of the yellow arrow). This should push the white plastic vent out. Pictured below is the vent body halfway out. The 2004-2005 VW Passat TDI fuel vent body is black instead of white. Clean the o-rings and backflush the vent tube to prevent dirt from getting pushed in when you put the vent back.
    [​IMG]

    You don't push the black plastic tube out, only the black button and the parts inside the black plastic tube. It will look like this (below). There are two tabs holding the vent internals in the vent body, pull them slightly out and the vent internals should come out under spring pressure. You can discard or keep the vent internals. Marked with a white arrow below was where you had to push up during the last step (vent is upside down).
    [​IMG]

    Backflush the vent tube with carb or brake cleaner (not water) to keep the vent tube clean.

    Put the vent body back (minus the internals) and make sure the white tab snaps the vent body back in place. The vent internals are now removed, letting you vent faster and easier.

    New beetle TDI fuel tank vent additional notes
    You can remove the vent in the NB 2 ways. The first way is identical to the above instructions. The second way may be easier, you remove the right taillight to get access to the back of the vent. Instructions for the NB are below.

    Open the rear hatch and pry off the oval taillight cover on the inside of the car. Unscrew the plastic knob that holds the taillight in place.

    Insert a screwdriver at the 8 o'clock position looking at the light to release a metal clip holding the taillight. Remove the taillight. If the taillight doesn't come out easily, the clip is still holding the taillight.

    You can now access the vent body from the rear instead of removing the fuel filler door and rubber surround. The rest of the instructions are identical to the above. Below is a picture of the vent as viewed through the rear taillight position.

    [​IMG]