Venting your diesel

leonsmith · Post by **leonsmith** » Mon Aug 04, 2003 9:03 am

Over at http://www.tdiclub.com the guys talk a lot about 'venting' your diesel whilst filling it up, although i've not seen it mentioned here, and wondered if anyone else knew about it, or were even doing it routinely.

There is a small level just inside the filler neck which gets depressed when you screw the filler cap back on. As it's pressed, the lever opens a valve to let air into the tank. Obviously, this air takes up space meaning that you can't get as much fuel in as you might expect - I can often only get 40 litres into my 45 litre tank, even though it looks completely empty.

'Venting' is the process of pressing the lever a few times with the pump nozzle, whilst your filling, to allow the air to escape. By doing this, you can keep filling it all the way up, allowing you extra miles between fills.

There is some discussion about how much room you need to leave in the tank for expansion etc, but venting is generally considered normal practice for most of the tdiclub members.

Thoughts?

Sadgeek · Post by **Sadgeek** » Mon Aug 04, 2003 12:52 pm

I carried this out a couple of times on my Passat.

I didn't notice any extra going into the tank, as it all seemed to pour out through the overflow, and onto the road underneath.

Dare say I may have got an extra litre or so in, but hardly seems worth the trouble when you leave a smelly puddle behind too

ciden · Post by **ciden** » Mon Aug 04, 2003 6:58 pm

If you're talking about the vent valve in the filling neck...yeah I've used it several times - on my 1.6. You can fill the car to the brim - you get (Babe told me this) around 10L of extra fuel in there, but it's not good to let fuel stand in the pipe. Suppose it's ok if you go on long journeys and you gonna use up the fuel. I drive about 200k's before the fuel gauge starts moving. So I guess it's normal practice in any VW/Audi.

des_pd_ tdi · Post by **des_pd_ tdi** » Tue Aug 05, 2003 12:28 pm

Hmmmm. I'll try it on my car next time I fill up.

Problem is I fill up every 2+ weeks, so I'll have to wait, damn this glorious MPG

des_pd_ tdi · Post by **des_pd_ tdi** » Sun Aug 10, 2003 11:30 pm

Tried this yesterday and squeezed in an extra 5 litres. Ive just come back from Oxford and done 100 miles the diesel needle has moved to the first notch from full on the dial the one before quarter tank.

So I'm pleased. The MFA has a hard time coping and I saw my range comp rise by 50 miles on the way home so I'm well pleased.

100 miles done - 62 MPG

435 left on the range.

Not bad methinks. I'll try and squeeze more in next time.

bertJ · Post by **bertJ** » Sun Aug 31, 2003 4:46 pm

I've carried out the so called 'ventectomy' detailed at http://www.cst.cmich.edu/users/willi1gl ... /index.htm
on my wife's Polo 1.4 Pdi. The only difference is that the valve is to the right of the filler pipe, not the left as on Golfs, etc.
You can get another 10 litres of fuel in and there are no problems with expansion - apparently diesel expands hardly at all compared with petrol.
We get close on 600 miles out of a tank full and you don't have to fiddle about holding down the vent valve lever with the pump nozzle when filling.