It keeps you from filling the tank all the way up. It allows an air space for the fuel to expand when it gets hot. If the tank is completely filled to the top, fuel may be expelled from the filler neck when the fuel expands. I believe it is either a federal or EPA requirement. I don't know if the "vent" , as it come to be called, exists on all the VW diesels or only on the ones with the PD motors. I dont think it exists on the gassers. You won't hurt anything by venting the extra air out of the tank, a lot of people are doing it the get the extra range. Somewhere, either here or at tdiclub.com are instructions for removing the vent if you wish. The fuel cap presses this button in when you screw it on, and thus the slight wooshing sound if you didn't vent before hand.

The PD motors run the fuel through the head to get the fuel to the injectors, where it picks up a lot of heat. The excess fuel returns to the tank. I know my Beetle has a fuel cooler under the passenger side area but it don't know if it is cooling the fuel before it goes back to the tank, or before it makes it to the engine. I'll have to look closer at the tubing colors.

P.S. it will also help in future posts to mention the year of your Beetle and any mods in your profile, as there are slight changes over the years. e.g. going from the distributor injection diesel to the PD diesel in 2004.

 

The vent is put on ALL vws. it is only there for the expansion of GASOLINE> Diesel does not expand like gasoline does when it gets hot.

you can safely use the vent button to fill your tank all the way to the top in any TDI. I have performed the ventectomy on my TDI and have never lost a moment of sleep over it.

the fuel cooler is there on all automatic older TDIs because the fuel pump in the automatics is more powerful than the one in the manuals thus adding more heat to the fuel. I do believe that the fuel cooler is aded to all of the newer ones for the reason described above. (fuel thru head)

no worries using the vent or even removing it on the TDI to fill the tank all the way to the top.

 

The vent is there for the gas cars and they just leave it there for the TDI's rather than change the design. gasoline expands quickly under a far lower temp than diesel does. The vent is opened when you put on the cap. A bunch of people with TDIs remove the vent and just fill up all the way. I always vent and fill right up to the top where I can actually see the fuel. FYI- The fuel tanks on the TDIs are plastic rather than metal...


OK =Growler beat me to it...what he said.....Here is a thread about it http://www.newbeetle.org/forums/showthread.php?t=1366&highlight=ventectomy

 

Yep - I had a ventectomy done at a Raleigh area TDI GTG. Prior to the ventectomy, I would press on the button with the dispenser to fill it up.

 

Oh, Aaron, you're the MAN!

 

Can't find button

Wow. I've looked in my 04 NB to see if I see a button in the neck of the filler. I see a plastic piece but no button. Am I missing something or does my year not have it?

 

Wow. I've looked in my 04 NB to see if I see a button in the neck of the filler. I see a plastic piece but no button. Am I missing something or does my year not have it?

I would assume that yours has been removed already? When you fill up next time try pushing against it with the nozzle after the pump clicks off. If you dont hear air escape and see the fuel go down then yours is already removed. I am pretty sure it has been on every year.....

 

I bought it new and I've never had it removed. I don't see any button that the neck of the pump would hit. The only thing I see is a small black plastic u shaped thing in the neck of the filler.

 

Try pushing it in and pull up a little when you fill up. If you hear air coming out, that's it. I didn't know for a long time that the button was the vent thingy! For some reason, I thought it should look different. Oh yeah, it's on the opposite side of the fuel door.

Cori

 

With a gas NB, is it safe to vent the tank if you will be driving a long distance right away?

 

With a gas NB, is it safe to vent the tank if you will be driving a long distance right away?

this is probably the ONLY time it might be safe to use the vent to top off in a Gas VW. say if you were on a road trip (Roswell anyone) and were continuing to drive immediately you would be burning fuel faster than it could expand.

HOWEVER< iirc there are some charcoal filled things in the fenders on Gas cars that arent there on the Diesels. these are there to filter the gas vapors before they get to atmosphere.. not sure what would happen if too much raw gasoline got into them, might make them unuseable. and require replacement.

on a gas car, vent at your own risk. especially if you are in a state/area where they do emmisions checks.

 

If you vent on a gas car, it can very well make the charcoal canister screw up and it will trigger your cel and you will have to have it replaced. Then of course there is the other obvious chance of a major explosion....I personally would never do this on a gas car ever...Just my 2 cents....