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#1 S3 Fuel Expansion Tank
Posted: Tue Sep 08, 2020 5:53 pm
by JoeLondon
Ah.
So, I figured out why the car stinks so much of fuel if I fill up, I changed the gaskets on the sender and the blanking plate thinking that would be it. But, I filled up to check it and sure enough, plenty of fuel smell. Lo and behold I find 2 breather pipes on the side of the tank which are attached to absolutely nothing at all, so currently my expansion tank is the spare wheel well. What could possibly go wrong.
I'm guessing I need a tank of sorts attached to these points. Is this common to be missing? I can't seem to find the part available. I therefore assume if I do eventually find one I may need to part with the other kidney. Is there an alternative?
I need to check if the rest of the system is there, I see there is supposed to be a charcoal canister and a breather housing apparently, are these also located in the rear quarter?
#2 Re: S3 Fuel Expansion Tank
Posted: Tue Sep 08, 2020 6:59 pm
by madjack4
Hi i have done away with my expansion tank after a accident over 2 years ago the tank was destroyed i just blanked the pipes off and drilled a small hole in the filler cap i have had no problems at all i am just careful not to brim the tank then park in the sun in case it expands the fuel and overflows out of the breather hole in the cap
Regards
#3 Re: S3 Fuel Expansion Tank
Posted: Tue Sep 08, 2020 11:34 pm
by lowact
You should be able to see the expansion tank tucked away in front of the filler pipe:
The charcoal canister is in the engine bay, on the footwell bulkhead behind the battery:

#4 Re: S3 Fuel Expansion Tank
Posted: Wed Sep 09, 2020 9:24 am
by JoeLondon
Thanks both for answers - I know what I'll be doing today :)
Colin - you're batting 100% here sir. Thank you very much!
#5 Re: S3 Fuel Expansion Tank
Posted: Wed Sep 09, 2020 9:59 am
by JoeLondon
So, it's a negative on the expansion tank or ancillaries. So perhaps madjacks solution is a go for now, unless I can find a set of these things. Willing to bet they won't be cheap though. I might look at a jerry rigged setup, perhaps a rubber bladder of some sort or an expansion tank from something else.
I assume the carbon filter and breather housing just deal with vapours and no liquid fuel goes any further than the tank itself.
#6 Re: S3 Fuel Expansion Tank
Posted: Wed Sep 09, 2020 11:15 am
by AussieEtype
JoeLondon wrote: ↑Wed Sep 09, 2020 9:59 am
I assume the carbon filter and breather housing just deal with vapours and no liquid fuel goes any further than the tank itself.
If your car is a 72 UK car you will not have to worry about much of that - were not fitted with most of the stuff.
#7 Re: S3 Fuel Expansion Tank
Posted: Wed Sep 09, 2020 2:09 pm
by JoeLondon
Thanks Colin,
Yes, have now discovered that that is mostly US gear - so I have blanked the tubes off with a small looped hose and the breathing will now be done through the fuel cap. That was easy :)
#8 Re: S3 Fuel Expansion Tank
Posted: Mon Oct 12, 2020 10:29 am
by Adamski
Just for the record mine is a 72 UK car owned 42 years!!
I have a locking fuel cap that maybe has a vent but I have great pleasure in filling the car right up and never get any fuel smells,so it seems good as designed. (Makes a change!)
#9 Re: S3 Fuel Expansion Tank
Posted: Wed Oct 14, 2020 5:51 pm
by Adamski
I checked my locking cap and it's non vented. Mine's a 72 UK car. I get no smells.
I've had the tank out some years ago and forgotten the layout. The workshop manual talks about vent lines.
Can someone tell me how the tank is vented and where does it vent to? Thanks
#10 Re: S3 Fuel Expansion Tank
Posted: Wed Oct 14, 2020 9:29 pm
by lowact
72 US spec; charcoal canister on the bulkhead behind the battery.
#11 Re: S3 Fuel Expansion Tank
Posted: Wed Oct 14, 2020 11:57 pm
by AussieEtype
UK specs dont have that - I assume just vents into the expansion tank near the fuel filler.
#12 Re: S3 Fuel Expansion Tank
Posted: Thu Oct 15, 2020 7:21 pm
by Adamski
I suppose there must be an expansion tank up there somewhere but I wonder where it vents to?
I'm not even sure you can get a visual on it?
No smells in car,
#13 Re: S3 Fuel Expansion Tank
Posted: Sat Oct 17, 2020 10:42 am
by JoeLondon
I believe our UK car just vents to the filler cap enclosure, there's what I had assumed to be a drain hole in the corner of the enclosure, apparently theres a pipe running from that near the filler neck, to I guess the expansion tank (all missing on mine).
#14 Re: S3 Fuel Expansion Tank
Posted: Fri Jan 01, 2021 7:22 pm
by Sdinse
FYI
On the US 2+2 its tucked way up over the left rear wheel well (C pillar?) and mounted to the horizontal seam at the back of the wheel well.
#15 Re: S3 Fuel Expansion Tank
Posted: Sun Jan 03, 2021 9:13 am
by MarekH
IIRC, it does feature in the Parts Manual. There is also a full explanation in the tan coloured US Owners Manual, which has extra pages that the same Blue UK booklet does not.
kind regards
Marek
#16 Re: S3 Fuel Expansion Tank
Posted: Mon Jan 04, 2021 10:12 pm
by Adamski
On my UK car that drain hole goes through to the bottom as I poked a wire through it gears ago when wash water would accumulate in the area below the fuel flap. Well worth doing.Still don't know where yje tank vents to. Had it out years ago but forgot.
#17 Re: S3 Fuel Expansion Tank
Posted: Tue Jan 26, 2021 2:32 pm
by Sdinse
On my 71 US SIII it is vented to the carbon canister .
#18 Re: S3 Fuel Expansion Tank
Posted: Sat Apr 03, 2021 4:23 pm
by Fspp369
Following this link..
Could someone tell me how to get this expansion tank out from under the n/s/r body.
I’ve removed the two little screws that were apparently holding it, in but now it just rattles a bit but will not come out. I want it out to blast the body.
Peter
#19 Re: S3 Fuel Expansion Tank
Posted: Sat Apr 03, 2021 5:05 pm
by Bob.
Ho Peter,
The tank should have an insulation pad glued to it and the pad may be glued to or has stuck itself to the wheelarch.

#20 Re: S3 Fuel Expansion Tank
Posted: Sat Apr 03, 2021 6:14 pm
by Fspp369
Bob,
Heap of thanks ...sanity saver!!
Forum rides again.