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fuel leak from rear arch area?
Posted: Sat Jul 21, 2012 8:41 am
by e30-EVN
filled my tank up as im going up to see danthe on monday morning (never usually fill her up.!) and noticed every time i boot it she wifs real bad of fuel... the smell is strong.!
ok so i pop into my local jetwash this morning and theres a left bend, give her the welly and when i pull up i notice she stinks, on the floor is a small patch of fluid, dip my finger and its fuel... look up into the rear arch and its wet there (roads are dry), it apears to be up and behind the plastic arch liner area where it is coming from.
what is behind this? and what is likely to be my issue here?
note - anything above 30 quid and when hoofed round left hand bends she stinks in the car, open windows and get rid of the smell for a bit and fine but can anyone please help or advise me as this is obv not ideal
thank you

Re: fuel leak from rear arch area?
Posted: Sat Jul 21, 2012 9:24 am
by mash
The fuel expansion tank sits up in the rear o/s arch, maybe that's full/overflowing. Or a leak in the filler pipe.
http://www.e30zone.net/e30zonewiki/inde ... #Fuel_Leak
Re: fuel leak from rear arch area?
Posted: Sat Jul 21, 2012 9:32 am
by e30-EVN
thanks for the link mate. the car had a brand new fuel tank and associated bits in 2010. i have a reciept here for over 400 quid (the last owner had it done).
what is this fuel expansion tank? can it be removed and the pipes plummed to bypass ?
Posted: Sat Jul 21, 2012 10:07 am
by mash
Its to trap overspills.
Such as when you fill up and go hard around bends
Take the arch liner out, see whats happening.
Looks like this:

Re: fuel leak from rear arch area?
Posted: Sat Jul 21, 2012 10:40 am
by E30BeemerLad
Ant, I used to get a similar situation of a stink of fuel if I wellied it or was a hooligan in a bend and it turned out to be the rubber O ring that sits at the top of the fuel pump/sender unit.
Re: fuel leak from rear arch area?
Posted: Sat Jul 21, 2012 2:31 pm
by Brianmoooore
E30BeemerLad wrote:Ant, I used to get a similar situation of a stink of fuel if I wellied it or was a hooligan in a bend and it turned out to be the rubber O ring that sits at the top of the fuel pump/sender unit.
This is more likely to be it. The collector tank itself doesn't normally give any problems, unless, as on one of my collection, some idiot had welded a patch in the inner arch, from the boot side, without bothering to remove the tank first
Re: fuel leak from rear arch area?
Posted: Sat Jul 21, 2012 5:38 pm
by e30-EVN
Thanks for the replies gents, since my last post I ripped the plastic liner out and took a look.
All the nipples on the expansion tank were fine and no sign of any hole or crack on the tank itself... Chopped a section of the vent hose off and fitted a new piece.
Then took her for an enthusiastic left half doughnut in a carpark. Imediatly stopped and noticed fuel dripping from the arch area onto the floor, did a bit more digging and found a 5 pence piece hole in my filler pipe near the top.!!
What looks to be happening is when hoofed round a lefty the fuel heads up towards the fuel cap and exits through the hole.!
So I found some repair bandage and leak or pipe fix and sealed it for now. It doesn't do it now.
Lee - the fuel pump is new as is the seal. Replaced this before thinking the same. I only found the hole in the pipe when I removed the round rubber surround from the filler neck area. Not happy. How much are these nowa days?
Re: fuel leak from rear arch area?
Posted: Sat Jul 21, 2012 8:51 pm
by mcbonio
Yep as e30-dk says, fuel filler neck.!
I had the same issue when I filled it more than half a tank full, it stank around the rear drivers side wheel arch. Lots of digging and poking revealed a 50p sized hole in the top of the filler neck.
You need to knock off all the dried dirt around the area and give it a good poking with a screw driver.
If this is the case, they are quite easy to change too so dont worry! Easy job.!
Re: fuel leak from rear arch area?
Posted: Sat Jul 21, 2012 10:22 pm
by DanThe
Find a decent one and get it sand blasted and powder coated, then waxoil it before fitting. It wont bother you again

Re: fuel leak from rear arch area?
Posted: Sat Jul 21, 2012 10:32 pm
by Brianmoooore
I assumed that the £400 included a new filler pipe, but I suppose the £400 includes a hefty labour charge as well as parts. As Dan says, find a good second hand one (you won't want to pay BMW for a new one!), get it tarted up, and fitted.
Re: fuel leak from rear arch area?
Posted: Sat Jul 21, 2012 11:15 pm
by e30-EVN
Think I will do that then mates, yeah the bill of sale was over 400 quid. I think the last owner got knocked but I've ended up with a brand new tank for bugger all lol so it can't be bad.
Its amazing the amount of crap that was behind the metal cover that hides the vent pipes ect (which incidently is also buggered), you would think bmw could have designed something a bit better to be honest.!
I've used repair bandage and leak pipe fix. Its oil and petrol resistant so will do for now
Thank you guys
Re: fuel leak from rear arch area?
Posted: Sat Jul 21, 2012 11:31 pm
by mcbonio
Yeah about 5 pounds of soil came out of mine.! Good stuff.!
Re: fuel leak from rear arch area?
Posted: Sun Jul 22, 2012 12:03 am
by e30-EVN
Shocking isn't it.! They could have made it a more sealed arrangement

Re: fuel leak from rear arch area?
Posted: Thu May 02, 2013 1:21 am
by e30pigeon
I have noticed drips of fuel falling from my touring, that are making the ground damp under the rear door in front of driver-side rear arch.
Is it still safe to drive the car?
Is this likely a fuel filler in need of replacement, too, or something else?
Thanks!
Re: fuel leak from rear arch area?
Posted: Thu May 02, 2013 7:28 am
by Grrrmachine
The leak will be caused by any of the options already mentioned in this thread. You need to examine it yourself to identify which one it is.