Fuel Tank Leaking

[Neil Thompson]

after filling my fuel tank to the brim i soon find a heavy discharge of fuel onto the exhaust pipe, not healthy!, I immediately drained the fuel and removed the tank. Problem is the tank looks fair to good condition even above the seam and i cant see where the leak is from. Now it's off is there an easy way to test?, I always run the car fairly full but this time I fully filled it for the Euro Event. One thing I did notice was the filler neck gasket was fairly contaminated on removal, is there a small, small glimmer of hope that I overfilled it and it's overflowed somehow?, as usual, any help appreciated but as quick as poss please gents, ferry leaves Thursday!

Neil

[jameshoward]

I suppose you've checked that all the hoses/return hose fine, and that the hose is new enough/jubilee clips secure? The hoses corrode. Give them a squeeze and see if they're wet or if the rubber has perished. There's the filter in the milddle of the tank (large round one with the hex head on the underside) which has a rubber o-ring, but if you haven't touched it the chances of it leaking would seem slight. Did you drive the car before you noticed the fuel or fill up on a slope? Wondered if it is possible that if you have over-filled that some fuel could have leaked past the cap and out of the tank. I've done that before.

[Neil Thompson]

Thank James, all the hoses good pump end. The leak was from the top of the tank opposite side to the pump, exhaust side. It is the fullest I have ever filled it and looking at a picture i took (attached) the area around the sender unit is very clean as if washed off. The other area that concerns me is the foam external gasket near the filler neck which to me looks contaminated, I'm thinking it may not be the tank at all. Tomorrow early I plan to clean a few suspect areas on the tank, block the two hose outlets, stand on end and re fill with petrol.

Neil

[Neil Thompson]

Crisis Over, for now!', got up early, degreased and dried the tank, blocked off hoses etc, refilled with fuel and checked for leaks. Petrol poured out from the sender unit on the top of the tank, tightened the bolts and cured. Which before anyone tells me I know it was a 5 minute job from inside the boot without removing the tank! Never mind, I am learning - even if it is the hard way

Neil

[Peter van Es]

The cork seal at the top may need replacing... it dries out and loses its sealing properties...

[JamesL]

Can Mrs Neil have her saucepans back now you've taken all the fuel out of them?
Congrats of finding a solution!

[Neil Thompson]

Ha, thanks Tosh, I've just got it back together and filled it to the brim again - no leaks!, I'm now not going near the car again until we set off Thursday afternoon, Hope yours is easily solved and will see you in Belgium Friday.

Neil

[tel76]

As a matter of interest i tried to purchase from MB a new tank sender gasket a few weeks ago,i was told they were NLA and i would have to buy a new sender unit.
I purchased some cork gasket material and made my own.

[gboyd]

Hi:
I have a 70Sl and I have noticed a strong gas smell.  Under the tank, I found that there is a tiny bit of fuel coming from around the front mounting stud.  I am wondering if I may have the same issues stated here or if it could be more serious.



Greg

[Neil Thompson]

Greg if you look at the photo of the tank in the earlier post you will see the shape of the tank near the sender unit aims any fuel to the front mounting, if it is worse when full, lift the inspection cover up in the boot (Trunk?) and check/tighten the 8mm bolts

Neil

[gboyd]

Thanks Neil.  I just tightened up the bolts, and they did seem a little loose.  I went out for a spin ( top down, oh so nice), took some hard corners, did a few strong stops and starts.  Then I checked to see if there was a drip.  Nothing noticeable.  Tats good.  But my trunk still smells like a fuel depot.  And it is definitely coming from the fuel sensor cap.  Now that I have taken that little plastic cover off it definitely seems to be my shell problem.  Could it be the cork gasket I need to replace to remedy this smell?

[Neil Thompson]

possibly so Greg unless the fuel which was leaking has soaked the 'tar' insulating pads on the top of the tank. If this is the case it may smell for a while but will dry up in time

Neil

[71Beige280SL]

Neil,

I recently had the same problem. My mechanic inspected the tank and it was compromised on the top in several areas. See the attached photo. If you look closely, you will see a wet look on the right side and some corrosion. You will also notice some major seepage where the filler neck meets the top of the gas tank (upper left). I noticed your tank has the same wet look on the top...might be the same set of issues. My tank was repaired 2 years ago. As a safety precaution, I chose to replace the tank.

[MrAZ]

A leaking non-vented gas cap will also produce symptoms of a fuel leak.  Using a level, I noticed that the gas tank is bolted into the car with the front of the fuel tank seam about one inch lower than the rear.  My cap leaked when the tank was near full.  Gas ran down the neck and onto the top of the tank where it travelled toward the front of the car (since the tank is mounted in a "downhill" manner).  Fuel then blew toward the back  when the car was driven.
Also, be careful to not use rubber vacuum hoses for the venting hoses, use rubber fuel line.  Plain rubber vacuum hoses will quickly rot.

[Neil Thompson]

Your photo, 71Beige, shows heavy leakage from the sender unit exactly as mine was, the area to the right doesn't to me look a vulnerable area unless its chafed against the boot (trunk) floor, the areas I worry about are the filler neck to tank area and also the seam areas

Neil