Petrol leakage on full tank fill

[ktteoh]

folks, i have heavy petrol smell and leakage from the center top of the tank coming down.

what are the possible causes? everything is well if my tank goes below the 1/2 mark on the gauge.

[shogun]

that is one of the hoses from the expansion tank which sits in my car under rear right wheel well next to the gas tank filler cap. You have to remove the wheel, the inner palstic cover and then all is in front of youe yes. Buy new hoses and clamps, the old hoses are hard like stone and brittle or already broken.
or nr. 4
http://bmwfans.info/parts/catalog/E34/Touring/Europe/520i-M50/RHD/A/1993/march/browse/fuel_supply/expansion_tank_tubing/
http://bmwfans.info/parts/catalog/E34/Touring/Europe/520i-M50/RHD/A/1993/march/browse/fuel_supply/

[e34.535i.sport]

folks, i have heavy petrol smell and leakage from the center top of the tank coming down.

what are the possible causes? everything is well if my tank goes below the 1/2 mark on the gauge.

When I had the same problem and investigated all around... It ended up being the pipe that begins at the back of the fuel tank. Replaced the pipe and no issues since... Easiest way to check is to see where the petrol is coming from by wiping it clean and watch as it travels down the tank. Mine was clearly coming from the back! I had to undo the two straps and lower the tank a little to change the pipe... (I think there's also a little bolt at the filler neck IIRC) - The best tip I can give you is to remove the rear bumper, it's only two nuts under the plastic strip that runs right across it. Makes life MUCH easier.

[ktteoh]

shogun, some questions:

1. can i just use any standard fuel hoses [similar inner diameter ones] and cut it according to the shape and run of the old hoses?

2. do i need to drop the tank as well to access all the hoses - how many altogether?


that is one of the hoses from the expansion tank which sits in my car under rear right wheel well next to the gas tank filler cap. You have to remove the wheel, the inner palstic cover and then all is in front of youe yes. Buy new hoses and clamps, the old hoses are hard like stone and brittle or already broken.
or nr. 4
http://bmwfans.info/parts/catalog/E34/Touring/Europe/520i-M50/RHD/A/1993/march/browse/fuel_supply/expansion_tank_tubing/
http://bmwfans.info/parts/catalog/E34/Touring/Europe/520i-M50/RHD/A/1993/march/browse/fuel_supply/

[ktteoh]

could you let me know which pipe is that from the diagram links that shogun pasted above?


When I had the same problem and investigated all around... It ended up being the pipe that begins at the back of the fuel tank. Replaced the pipe and no issues since... Easiest way to check is to see where the petrol is coming from by wiping it clean and watch as it travels down the tank. Mine was clearly coming from the back! I had to undo the two straps and lower the tank a little to change the pipe... (I think there's also a little bolt at the filler neck IIRC) - The best tip I can give you is to remove the rear bumper, it's only two nuts under the plastic strip that runs right across it. Makes life MUCH easier.

[Bo525i]

I´m following this as my 530 has developed a similar leak..

[Mr._Graybeard]

I've had the gasket around the fuel pump leak pretty badly on an E30. I wonder if the same thing could happen on an E34.

[e34.535i.sport]

could you let me know which pipe is that from the diagram links that shogun pasted above?

#2 where it joins to the tank with hoseclamp (#20) in this diagram: http://bmwfans.info/parts/catalog/E34/Touring/Europe/520i-M50/RHD/A/1993/march/browse/fuel_supply/plastic_fuel_tank/

[sal_park]

Hi,

I'm not sure the link provided by shogun is correct for a late E34 - at least it looks different looking to my 94 525 (admittedly a rhd uk model). Early E34s had a metal fuel tank and later ones had a plastic one. I suggest entering your chassis number in realoem.com and seeing what options it gives you. My E34 (M50 525 rhd) gives me this diagram:

realoem plastic fuel tank diagram (http://www.realoem.com/bmw/showparts.do?model=HD52&mospid=47375&btnr=16_0041&hg=16&fg=05)

and the pipe I had to replace was #2. As e34.535.sport has said you'll need to lower the tank 'a bit', depending on what tools you have available (a dremel would be very helpful here). +5 for taking the bumper off.

Don't even think of thinking about fixing this without first taking the bumper off.

You'll need to remove the black strip around the bumper - comes of in three parts. push the shorter sides parts back to reveal two plastic screw type things - turn them 90 degrees and them pull. They will come out. Eventually. With these out remove the (19mm ? not sure) nuts under the longer trim piece and it should come right off backwards. Here's how it will look with the bumper off, and you can see the pipe #2 in the picture:

http://farm4.static.flickr.com/3570/3357811424_44a3d6ab85_o.jpg

The pipe I replaced was only 20 GBP (from the dealer, 7 days lead time), so probably worth getting over generic fuel hose as it is mostly metal and clips onto the fuel tank. (Strangely I do remember having to buy some fuel hose too, can't for the life of me think why though).

Anyway, this is what the rusted hose look like before replacement:

http://farm4.static.flickr.com/3459/3357057961_890419fbc9_o.jpg

hth

sal

[e34.535i.sport]

+1 on dealer pipe, not expensive at all.

How did you find clipping it back in on the little plastic pieces? The pipe wasn't quite the same shape as my tank so had to leave it out in a couple of places! :p

"Strangely I do remember having to buy some fuel hose too, can't for the life of me think why though" - The other end joins to the tank with a short (3"?) piece of rubber pipe IIRC?! That's where mine was leaking from... :(

[sal_park]

- The other end joins to the tank with a short (3"?) piece of rubber pipe IIRC?! That's where mine was leaking from... :(

That's right - you've jogged my memory. The piece of rubber pipe you're talking about is on the end of the metal pipe that is under the spare wheel well and is the other end to the one pictured in my post above. Given the leak was at the rubber / metal join I figured that I'd replace both pieces to save going back in there (medium arse) and empty a full tank of petrol again (big arse).

BTW the size of the fuel pipe is not obvious, but the part from the dealer had it stamped on it some where.

[sal_park]

How did you find clipping it back in on the little plastic pieces? The pipe wasn't quite the same shape as my tank so had to leave it out in a couple of places! :p

While I was clipping the pipe into some of the plastic clips (using a wooden hammer :) ) there was a couple of 'it'll clip in or break' moment :D

[e34.535i.sport]

While I was clipping the pipe into some of the plastic clips (using a wooden hammer :) ) there was a couple of 'it'll clip in or break' moment :D

LOL! Glad it wasn't just me! :D

[shogun]

I am not sure which tank he has, so he has to check the part numbers based on his VIN. But if I would do it, I would replace all hoses at the same time, thenthat problem is fixed for the next +10 years, otherwise he has to do the same probably on another hose the in the near future.
For the hoses and clamps I used standard fuel hose (not BMW) from the parts shop around the corner based on existing sizes.

[repenttokyo]

my tank does the same thing due to seam corrosion at the top of the tank.

[ss2115]

I have the same petrol smell only when full on my 93 525i Touring.
I know that I'll have to hunt around to find one or more poor hoses but is there any one or more hoses that are more common or more likey than others?
ie: could anyone suggest the best most likely place to start?

It only smells for the first 1/8 of the tank and then disappears, but if I'm only between home and office that can be almost a week of petrol smell.
Its inside the car as well as outside.

I'm pretty sure the tank is plastic.

[e34.535i.sport]

I have the same petrol smell only when full on my 93 525i Touring.
I know that I'll have to hunt around to find one or more poor hoses but is there any one or more hoses that are more common or more likey than others?
ie: could anyone suggest the best most likely place to start?

It only smells for the first 1/8 of the tank and then disappears, but if I'm only between home and office that can be almost a week of petrol smell.
Its inside the car as well as outside.

I'm pretty sure the tank is plastic.

If there's only a smell but no leak you could have the issue I had... (I've had a few petrol wise!)... There's a vent pipe which was seriously corroded on mine and caused a smell but obviously no leak. Get the rear right hand wheel off and remove the plastic cover as Shogun said... It will be blatently obvious if it's anything like mine was... The fuel filter is also in the general vicinity so might be worth replacing that if it hasn't been done and you're going to change some pipes too? Have a look sooner rather than later ... When a fuel pipe goes it's always at the worst possible time so don't wait until it's too late!

[leicesterboy15]

I've had the same problem on both my e34s, both times it was the vent pipe attached to the tank behind the rear bumper, I've had all sorts of explanations for the leak from mechanics, one even said I had a metal fuel tank! A simple magnet test confirmed that this was wrong! Apparently a metal fuel tank was only used in tropical climates and I couldn't source one in the UK - all were plastic, I don't think it relates to age of car, my e34s were 1989 and 1996 and both had plastic tanks. The parts guys and mechanics I spoke to all said they'd never seen an e34 with a metal tank in the UK anyway.

BTW the plastic tank was £600 from BMW and the metal one was £300 IIRC, not sure how they worked that one out but there you go....

[repenttokyo]

my car has a metal fuel tank, and canada is NOT tropical!

[tim eh?]

yeah I had a metal tank, you could tell from all the rust :D. replaced it with a (iirc) $700 metal tank - it wasn't anywhere near the biggest bill i ever had but boy was it ever tough to fork over for that.... i thought a metal tank was my only option, would a plastic tank be better? not that i'm going to change it again .

http://www.bimmernut.com/forum/attachment.php?attachmentid=5425&stc=1&d=1234306624

[e34.535i.sport]

replaced it with a (iirc) $700 metal tank

Mate that musta stung! Least you have peace of mind for a LONG time now. :)

[tim eh?]

yeah it was harsh but gas tanks aren't the kind of thing you want to buy used around here as you can see, and it had already been repaired once. It was a serious 'do i keep this effing car? is it worth this pain and torment?' moment but as you say i don't worry about the gas tank anymore at least.:D

[ktteoh]

folks, looks like my petrol tank is leaking from the upper side. seems like i need to take it TOTALLY out to see what's going on.

what are the steps involved to remove a petrol tank DIY [since i assume it's dangerous with all the fumes etc].

is there any good guide out there.


Hi,

I'm not sure the link provided by shogun is correct for a late E34 - at least it looks different looking to my 94 525 (admittedly a rhd uk model). Early E34s had a metal fuel tank and later ones had a plastic one. I suggest entering your chassis number in realoem.com and seeing what options it gives you. My E34 (M50 525 rhd) gives me this diagram:

realoem plastic fuel tank diagram (http://www.realoem.com/bmw/showparts.do?model=HD52&mospid=47375&btnr=16_0041&hg=16&fg=05)

and the pipe I had to replace was #2. As e34.535.sport has said you'll need to lower the tank 'a bit', depending on what tools you have available (a dremel would be very helpful here). +5 for taking the bumper off.

Don't even think of thinking about fixing this without first taking the bumper off.

You'll need to remove the black strip around the bumper - comes of in three parts. push the shorter sides parts back to reveal two plastic screw type things - turn them 90 degrees and them pull. They will come out. Eventually. With these out remove the (19mm ? not sure) nuts under the longer trim piece and it should come right off backwards. Here's how it will look with the bumper off, and you can see the pipe #2 in the picture:

http://farm4.static.flickr.com/3570/3357811424_44a3d6ab85_o.jpg

The pipe I replaced was only 20 GBP (from the dealer, 7 days lead time), so probably worth getting over generic fuel hose as it is mostly metal and clips onto the fuel tank. (Strangely I do remember having to buy some fuel hose too, can't for the life of me think why though).

Anyway, this is what the rusted hose look like before replacement:

http://farm4.static.flickr.com/3459/3357057961_890419fbc9_o.jpg

hth

sal

[sal_park]

folks, looks like my petrol tank is leaking from the upper side...

Hi ktteoh,

when you say upper side what do you mean ?

do you mean below the 'M' in my picture earlier in the thread ? Or perhaps from around the fuel pump / petrol gauge hatch ? (open the black cover under the boot carpet on the right hand side - see pictures of hatch here (http://www.bmwe34.net/Wiki/tiki-index.php?page=Fuel+pump)

sal

[ktteoh]

by "upper side" i meant the upper side part of the tank that meets the body of the car ... all i can see if petrol stains dripping from the upper side, and trickling down the sides [rear & right sides] of the tank.

i know the above is clear as mud but hope it somehow clarifies ..

btw i look at your link on the black hatch - is there a gasket between the plate cover [where fuel pump & sender linkage is attached to] and the actual surface of the tank? - maybe that's where it's leaking on mine..


Hi ktteoh,

when you say upper side what do you mean ?

do you mean below the 'M' in my picture earlier in the thread ? Or perhaps from around the fuel pump / petrol gauge hatch ? (open the black cover under the boot carpet on the right hand side - see pictures of hatch here (http://www.bmwe34.net/Wiki/tiki-index.php?page=Fuel+pump)

sal

[Derek A.]

I had the same thing. Developed a small crack in the sheet metal - I would get gas smell and a little drip when full. I tried a JB weld patch - but it started leaking again worse. The only solution is to have the tank professionally repaired or replace it.

[Bo525i]

I just changed the other pipe running to the fuel tank, the one on the front of the fuel tank, same clips..

Major PITA without dismounting the fuel tank all together (which I didn´t, no lift and raining too), all lot of crawling on your knees to get the new one back in where the old one was!

Rear changed some months ago and that one is real easy to change in comparison!