At the request of another member, I have been asked to post up this "how to" guide.

I have done this mod on both my Golf Tdi & my wifes Fabia Tdi, it takes about fifteen minutes to do and it has given us both extra tank capacity, quicker filling and caused absolutely no problems whatsoever.

This is a short guide on how to add about five litres or so extra capacity to your diesel tank and should only be attempted on DIESEL engined vehicles & definitely NOT on petrol engined vehicles.

It is known as the "ventectomy" mod, very common in the U.S.A. and a quick search of this site will cover all the arguments for and against carrying it out.

For those that wish to try it, the procedure is simple and is as follows:

1. Open fuel filler door.

2. Remove Torx screw.

3. Unscrew fuel cap.

4. Remove fuel flap door and inner trim by carefully pulling out at screw hole and moving the whole item (door, seal & drain pipe) towards the rear of the car the whole assembly should come out.

5. The plastic drain hose can be pulled out with the assembly.

6. On the right of the fuel filler neck you will see a black plastic bit protruding out about one inch (on the left on a Golf) The valve you wish to remove is inside this bit & white in colour. Using flat screwdriver it's possible to remove the valve by pushing the white tab in and at the same time levering the valve outwards. This is done via the slot where the valve can be seen in the black plastic outer. It should be levered out away from the filler neck while pusing inwards on the white tab. It helps to push on vent "button" from inside filler neck as well.

7. Remove white valve assembly THIS IS IMPORTANT remove the valve, spring & retainer from inside the white valve assembly and REFIT the white assembly minus the valve etc to the car.

8 Refit the filler door & seal, and secure with torx screw.

Enjoy extra tank capacity & vent free filling !

Pictures of this job being done on a Mk4 Golf (virtually the same) at this link:

Removal of the Fuel vent in an A4 Golf/Jetta

great guide! - I've filled to the brim after this mod and left the car in the heat - no overflow or any other probs - used it for over a year now - absolutely safe for a DIESEL.

On my fabias I used to refill whilst pushing the black nozzle down which gave extra capacity, however my octavia vrs tdi does not seem to have any vent system and I get about the same amount in as the fabia despite the capacity being listed as 10litres more.Any ideas with the octavia?

Will this effect the automatic pump cut off when the tank is full?? If not then I think I'll give it a go!

Will this effect the automatic pump cut off when the tank is full?? If not then I think I'll give it a go!

No it doesn't affect the cut off but you get a sort of bonus warning of the kind of sound you get when a milk bottle is filled from a tap so you know when you're nearing full !

As per Basil I've had both vehicles (Golf & Fabia) modded like this for quite a while now and done a couple of friends vehicles with no problems.

I am a little dubious about this mod . . . is there any chance of fuel coming out if you go around a sharp left hand corner soon after filling up? Reason for me asking is diesel on the road, unlike petrol, won't evaporate readily and seeing as it would probably (if) spill on a corner, would mean other vehicles negotiating that bend would have a nice slippery diesel patch to contend with.

Not trying to put a damp teatowel on anything, I used to brim fill my fabia, but this thought occured to me a while ago and I thought I should mention it in the light of this thread.

I'd hope the filler cap does provide some sort of seal?

I am a little dubious about this mod . . . is there any chance of fuel coming out if you go around a sharp left hand corner soon after filling up? Reason for me asking is diesel on the road, unlike petrol, won't evaporate readily and seeing as it would probably (if) spill on a corner, would mean other vehicles negotiating that bend would have a nice slippery diesel patch to contend with.

Not trying to put a damp teatowel on anything, I used to brim fill my fabia, but this thought occured to me a while ago and I thought I should mention it in the light of this thread.

No sign of this happening at all, being a motorcyclist were this to be the case I would never condone this mod !

Hope that helps.

This is something i'm toying with myself rather than standing there holding the spring loaded switch with the fuel dispenser etc.....

Isn't the filler flap release cable going to need to be detached / re-attached at some point during this as i can't see any mention of it in the guide and i was under the impression it was a git to fit if ever it came off anyway.

Cheers

Dave.

This is something i'm toying with myself rather than standing there holding the spring loaded switch with the fuel dispenser etc.....

Isn't the filler flap release cable going to need to be detached / re-attached at some point during this as i can't see any mention of it in the guide and i was under the impression it was a git to fit if ever it came off anyway.

Cheers

Dave.

Nope, you don't need to touch the cable. The filler cap catch is attached to the body of the car (you can see it in the photo) and the whole door assembly comes off leaving this in place, easy, peasy !

Nope, you don't need to touch the cable. The filler cap catch is attached to the body of the car (you can see it in the photo) and the whole door assembly comes off leaving this in place, easy, peasy !

Nice one..... Might have a go this next week or two.

Cheers

Dave.

I've done this mod today, thanks for the guide!!

I've taken a few extra pics, and will make a Passat specific guide on UK Passats. I will refer back to this guide and credit you Td-eye!

UK Passats :: ukpassats.co.uk :: View topic - Increase your diesel tank capacity - ventectomy.

Thanks again for the guide td-eye

http://www.bmf.co.uk/upload/documents/1195475712_dp01__diesel_poster.pdf

i just push the little bit down with the end of the fuel pump and it fill the extra bit up as well that way dont need to take car apart

i just push the little bit down with the end of the fuel pump and it fill the extra bit up as well that way dont need to take car apart

take it your talkin bout wee black button type thing 2" down on left of filler m8???

http://www.bmf.co.uk/upload/documents/1195475712_dp01__diesel_poster.pdf

I couldn't agree more with the sentiments in that link, I am a motorcyclist, BMF Member & VJMC member.

What I fail to understand though is why you attach it to this thread about the "ventectomy mod" ?

If you are somehow trying to insinuate that by doing this mod you will some how spill diesel on the road, please try and fully understand what the modification entails.

The expansion tank and vent valve (modified or unmodified) is part of sealed system and vents back into the tank under the fuel filler cap & in NO WAY will cause any diesel spills.

Please clarify why you are posting this ?

I would NEVER condone ANY diesel spillage.

The modification is to increase your tank capacity is it not?

Where exactly is this extra capacity coming from?

Is it gained by filling the expansion tank with fuel?

Is it relying on the filler cap to stop spillages?

If the tank is full, and the expansion tank is full, where will the fuel go on a hot day?

The sentiments in the poster are:

- Don't overfill your tank

- Do leave room for the expansion of diesel in your tank

Are you not doing the opposite?

Diesel expansion is negligible, in the case of the fuel tank and temperatures its as good as non existant.

This news release by the RAC Foundation highlights the dangers of overfilling the fuel tank with diesel. If the tank is brimmed, and the fuel filler cap is then inadvertently left off, there is an increased risk of diesel spillage. As with any mods, I believe that insurance companies would expect this one to be declared.

RAC Foundation - KILL SPILLS 2006: FILL IT, DON'T SPILL IT SAYS RAC FOUNDATION

just a question car comps are interested in saving money so why would they fit this valve if not needed?

Just a question i have no knowledge on the subject

Three points.

1)The co-efficient of expansion of diesel is negligible (search for previous posts on ventectomy for further info on this) .

2) The filer cap on the Fabia is designed not to allow diesel to leak out although granted (without stating the obvious) if you forget to replace the cap with or without the mod, it may actually spill out !

3) I can see nothing in this mod that would suggest it might cause diesel to spill and likewise from personal experience I have seen no signs of diesel spill on any of my vehicles. Furthermore, I have not heard of one instance of diesel spill following this mod on the hundereds or more likely thousands of such mods carried out in the U.S.A.

As stated previously if I thought for one moment this mod could cause diesel spills or if anyone can provide hard evidence of this, I will not condone it !

just a question car comps are interested in saving money so why would they fit this valve if not needed?

Just a question i have no knowledge on the subject

It's needed for the petrol engined models.

It's needed for the petrol engined models.

ahhh another problem solved

if...the fuel filler cap is then inadvertently left off...

If the driver is dim enough to forget to put the fuel cap on, especially when all the Fabias I have seen have the cap attached to the car, do you seriously think they would be bright enough to follow this guide?