Serious help please - got a fuel leak

[jesters3]

Got home tonight and saw a water trail following my car, on closer inspection it was frikking petroleum from my car!!! Open the cap and it just ****** out everywhere so had to hold the cap on to let the gas out. you can hear it chugging away underneath as it is emptying. I have changed the fuel filter and taken it for a spin but the pressure still builds up and ****** the fuel out.

Any ideas what else I can look for?

 

[S3 Dave]

Sounds bad where is it leaking from?? Nothin to do with the increase in temperature today silly as it sounds??

 

[jesters3]

It is coming out of the cap as the pressure is just building up so much that is is spewing out. Had a good look underneath and could see see any obvious leakage spots but unless I take the bumper off I don't know for sure.

I do agree with the temp thing as it has happened a few times before (build up of pressure) but this time it was BAD!!

I've dug through my Haynes Manual and all else I could see that could cause this is the fuel pump or the fuel pressure regulator at the front. Anyone know of ways to test etc

 

[jojo]

Coming out the cap as in fuel cap?

 

[j4jon]

How much fuel do you have (did you have)? My dad had something similar on his mondeo, when he had more than 1/2 tank fuel the pressure would build up and it would leak from the seal where the filler pipe went into the tank. To fix it it ment dropping the whole rear beam and the fuel tank, it wasn't worth it on a car that was 9 years old and had done 200k so we got rid of it.

 

[simch]

You must have over filed it, there is a venting and expansion system on the audi tanks that can get full up with fluid if you overfill them or have done in the past.

I would take it for a 30 mile blast and use a gallon or so, then just monitor how much you have in there, when the light comes on to warn you of low fuel, then put about 47-48 litres in max. Thsi should leave you a galon space for expansion.

BTW dont park on your drive it will destroy the tarmac! Also, whilst petrol is quicker at evaporating than lethal diesel, be very careful to avoid this happennig, whether it be by getitng it fixed (ideally) or keepiung lower fuel levels. Such leaks can and do kill motorcyclists in wet conditions, so please be cautious!

 

[jesters3]

Well the pressure is building up somewhere in the tank. When opening the fuel cap you can feel the pressure behind it and it sprays the fuel out when you take it off so I have to hold it on and open slightly to release the pressure. You can hear something chugging away (fuel pump I think) underneath when the pressure is released. Popped the bonnet to check the fuel rail and regulator but nothing untoward or weird noises from there only the rear at the tank.

I don't believe it to be overfilling as I have run it to the low level light flicks on but still get this build up of pressure, I then filled it slightly with 10 litres and went out for a blat but when I got back it was ******* out - this time it was trickling down from behind the bumper so like j4jon mentioend it may be a seal that has popped or something as well as the pump working overdrive

I hear you on the leaks and will be cautious, I guess I better not have a fag on the way out tomorrow!
Anyway spoke to Storm and they will have a look at it tomorrow and hopefully route out the problem, they mentioned that it was a common thing the pressure due to heat and what not, but when describing it more and the extensive build up it looks more ominous then that. They know a few guys at Audi so will pick their brains as well to see if they know of anything. I thought about pulling out the pump to have a look but thought best not and just wait till tommorow.

 

[simch]

where do you live fella!? I'm coming round with a bucket, at 1.20 a litre it's well worth catching it!! LOL!


BTW I read on another forum of some diesel cars with plastic tanks being "drilled" when on peoples drive at night, and the diesel drained out!! WTF is this country coming too!!??

 

[simch]

BTW, lend your car to a mate that smokes who wants to give up, they ask him to take the fuel cap off for you! ! Job Done!!

 

[j4jon]

So what was the issue with you car in the end then?

 

[jesters3]

Nothing conclusive.

Fuel lines are clear
Pump is fine
N80 Purge Valve/EVAP system is fine

Only bits left are two hoses connecting the two tanks and the second pump. Storm took off the rear archliner and had a good route round but say the seals look good and no leaks apparent. They also spoke to their contacts at Audi and VW who say 'Thats a new one'; so they are stumped at present. I have had to give Audi a call to book it in and they say they should be able to take a look this afternoon once they get some courtesy cars back.

Gutted really as this is the last thing I need. Still been looking at Autotrader and see a nice 07 8P S3 going......just got to find a spare £20k!!!

 

[abdus]

simch

breather pipes blocked?

 

[jesters3]

Audi called to say that they think it is the gravity valve that is causing the issue or one of the breather pipes; in both cases it is a fuel tank out job at 4.5 hours labour. The gravity valve costs £5 and the breather hose £10 but the flipping labour is over £500!!!. Managed to get a 15% discount due to the age of the car so all in £432.00. So it is booked in for the thursday to get sorted. I met up with the mechanic and spoke to him about it (i've known the guy for while, funnily he is called Guy) and he concurs the situation that Storm found that all is in order and the only two other options is this valve and hose; so fingers crossed it should sort it!

 

[simch]

4.5 hours to remove the fuel tank.....! What nonsense! !

Why not take it to an independant garage - they can spend 6 on it and it will be 40% cheaper!!

Stealers make me laugh sometimes!

 

[j4jon]

Is that Guy at Newbury, he always seems helpful when I've spoken to him.

 

[j4jon]

Thats why we got rid of my Dads Mondeo. Too expensive to get done at a garage and really couldn't be bothered to drop the petrol tank myself.

 

[jesters3]

4.5 hours to remove the fuel tank.....! What nonsense! !

Why not take it to an independant garage - they can spend 6 on it and it will be 40% cheaper!!

Stealers make me laugh sometimes!

I was waiting for you to say that.

Too be honest I wouldn't have a clue what to do in removing a fuel tank and but flicking through Haynes it is definitly way out side my remit. I thought the 4.5 hours is fair enough based on the the work and testing need to be done, still I ain't no mechanic so **** knows plus no way could I find the time to do it myself.

Storm are unable to do it as they are flat out and too busy and there are not really any other Audi specialists locally. There are some run of the mill ones round here but in that case I'll take it to Audi. That way I can feel relatively confident that it willl get sorted and if there are any other parts that are needed or some other fault found then it is a the right place to get what it needs to get back on the road. Plus I get a courtesy car which is what I need rather than sorting out a hire car if had to get Storm to sort.

 

[jesters3]

Is that Guy at Newbury, he always seems helpful when I've spoken to him.

Yeah thyats the one. He is a good sort and doing the work on the car so fingers crossed all is in safe hands.

 

[Lewis0292]

Sent from my iPhone using Tapatalk

 

[kosmamoczek]

If anyone ever finds this thread: this problem is usually caused by swapped fuel return/fuel tank vent lines. Under the hood, on the left, look for three fuel line connectors. They are color coded, and in my car they were swapped by a mechanic.. I literally registered to comment here because it took me two months to diagnose this.