Fuel Tank Leak

[sleepy81]

Smell outside RHS of car. Looked underneath & found this.



Found several links on this so will remove rear seat. May need to cut a hole.

[swanicyouth]

Try putting it up on jack stands and welding it.

[Larkin660]

Umm...weld the tank?

[m10n]

Yep mine does it only if filled up. I think it might be a vent hose but haven't dropped tank to deal with it

[legoman67]

remove the back seats and access panels and check the pump area and sender area on the other side. Its very likely its those seals that have gone bad. no need to drop the tank.

[mjrgroup]

The tank is plastic. You may be able to attempt a repair with the correct epoxy.

[Bluesman]

I had leak in my 95 looked like that. It was the rubber hose. R&Rd it, no leak. there is a write up somewhere on replacing it. its not hard. take back seat out and open visual cap turn ignition on and see where the leak is exactly. go from there.

[8eights]

Try putting it up on jack stands and welding it.

?

[sleepy81]

It was the rubber hose. R&Rd it, no leak. there is a write up somewhere on replacing it. its not hard. take back seat out and open visual cap turn ignition on and see where the leak is exactly. go from there.

Thanks all for the replies. My search for tank leak showed 3 posts including that one. I will report what I find when I remove the rear seats.
Weird thing is I always fill the tank right up. This leak though, is fairly substantial so I'm supprised there is such a major failure and not a small leak initially.

[bdiefAZ]

Other sources of fuel leaks are the fuel senders and seals, they can crack with age. My car needed a new fuel pump as a result.

[NevadaMike]

+++
I had the same leak pattern after Dealer replaced the fuel pumps. Dealer-induced failure.
Remove the rear seat and check the seals and connections on the top.

[wokke]

I had a bad leak on my yellow 850 as well and it turned out to be rotten rubber fuel hoses. Don't forget that they are most likely as old as your car

[sleepy81]

Removed the left rear seat & found this. Not pretty.



And under the sound mat and inside the top of the pump?, a pool of fuel. So how is it getting under the seat?








It seems the fuel is leaking past the metal bung in the floor & pooling on top of the tank and in the floor.
A day later I check again & the fuel again pooling on top of the blue plastic casting. Where is the pressure coming from?
Each time I mop it up, it seeps back.
I thought it was from the hose. The photo shows the crimped clamp but it is from a crack between the hose and the round protrusion shown just above it, but at the bottom where the fuel is now pooling.




Looks like a replacement pump is needed unless I can repair the crack.

[wokke]

I've been successful with repairing cracks like this using fuel and oil resistant sealant (Loctite 5910).

[TxGR8White]

I have also tried to "seal" the hairline crack that develops. Sometimes though, the "crack" is actually the plastic shrinking around the electrical connector pins, and this is where you will leak. The repair is temporary at best, it looks like you are in the market for a new pump carrier...

[sleepy81]

So it seems the complete RH carrier with pump at some $530

16141182290

is required. The bare left carrier at only $150 looks like it is not interchangeable.

[TxGR8White]

So it seems the complete RH carrier with pump at some $530

16141182290

is required. The bare left carrier at only $150 looks like it is not interchangeable.

Correct. Left side carrier is NOT interchangeable.

[sleepy81]

Found the leak in the corner of the casting at the tip if the knife blade.



Here is the tell-tail smudge on the inside and the line through it is the crack.



Tried to weld with a soldering tip but access was too limited. Roughed up with a dremel and glued an aluminium patch with some JB weld. I'll test the effect of fuel on the patch before I replace the pump.

[cartoonz]

realize that IF it works (big if), it will only be very temporary.
been there. done that. have the t-shirt.

[sleepy81]

Well its back in the tank. No leaks so far & a sample passed my test of the effect of fuel on JB Weld. Long term?? Easy enough to check from time to time.

[escomike]

I have searched high and low for the procedure for removing the gas tank so I can clean out 10 years of sludge.
Any bit of help would be appreciated!!

- - - Updated - - -

I have searched high and low for the procedure for removing the gas tank so I can clean out 10 years of sludge.
Any bit of help would be appreciated!!
Sorry I have a 91 850i

[Wuffer]

E31 Repair Manual, Section 16. Available for download here: http://www.wuffer.ca/index.php/downl...g-manuals.html

[8eights]

Thanks Tom!)

[escomike]

Wuffer thank you very much!

[clockwork]

I have also tried to "seal" the hairline crack that develops. Sometimes though, the "crack" is actually the plastic shrinking around the electrical connector pins, and this is where you will leak. The repair is temporary at best, it looks like you are in the market for a new pump carrier...

this is what happenning to mine. gas is leaking out through the 3 pin round connector, so I had to order new pump carrier (comes with new pumps too, which sucks cause 3 months ago i just installed 2 new Bosch pumps and filter, ugh, money wasted now)