Fuel System: Tank leaks when full

[Geigs]

Hi all,
When I fill the tank, it leaks until some fuel is used. Not a lot of fuel leaks out, but enough to make the garage reek. It seems to drip from the top, front end of the tank. Any suggestions on how to fix? Thank you.

[BobPalma]

Sure, Steve: Chances are excellent that the gasket around the fuel gauge sending unit is bad.

Get a new gasket and the requisite little copper washers for under the screw heads from one of our vendors. Replace it from inside the trunk. No need to drop the tank. BP

[joncon]

My 63 Cruiser was doing the same thing. The gas was coming out around the screws that attach the gas gauge sending unit. After the fuel level dropped in the tank it would stop leaking. I removed the screws and put some silicon on the threads and it stopped leaking. You might see if yours has the same problem.

[Geigs]

Thanks for the tips. I will give it a try.

[altair]

I agree with all of the above, I have a Lark tank out of the vehicle and I plugged all of the openings and pumped some air in the tank and the only place the soap bubbles appeared was around the fuel sender gasket.

[paintim613]

Sure, Steve: Chances are excellent that the gasket around the fuel gauge sending unit is bad.

Get a new gasket and the requisite little copper washers for under the screw heads from one of our vendors. Replace it from inside the trunk. No need to drop the tank. BP

I had same problem with mine. What Bob said. After unsuccessful attempts with rubber gaskets, a cork one finally solved the problem. Also, I don't fill tank completely anymore.

[TWChamp]

I had to install a new tank float when I bought my Champion last year. I cut the sender gasket out of rubberized cork that I bought at Fleet Farm. It held up fine, but now that I have the tank out to remove the 20 year old liner material, the gasket curled up, due to the crap gas it was exposed to. Does anyone know what material would be good and not be affected by crap gas? Thanks, Tom

[jrlemke]

If you use the copper rings, make sure you get soft copper. The first time I replaced the sending unit, I wound up with copper rings that were too hard and did not crush. They leaked after a very short time. Got soft copper and have had no leaks for 2 years.- Jim

[CJMiller]

If you use the copper rings, make sure you get soft copper. The first time I replaced the sending unit, I wound up with copper rings that were too hard and did not crush. They leaked after a very short time. Got soft copper and have had no leaks for 2 years.- Jim

If they're too hard, try gently heating them with a propane torch, don't go crazy just till they turn reddish. Then cool them in water. The faster you cool them the softer they become. It's temporary, the copper will harden again in time. The process is called annealing if you want to Google for more info. (I guess it goes without saying,but this isn't something done with the washers on the tank)

I couldn't get my sender to seal with the modern neoprene gasket. Once I made one out of rubberized cork it was dry as a bone even with the tank completely full.

[Skybolt]

I ran into the same thing years ago with my Lark. I replaced the original float/sender unit and had a leak at one of the screws. The car always smelt of gas, especially once parked in the garage, and after a drive I smelt of gas. I swapped out the cork gasket with a neoprene one I made myself and used a Loctite product on the screws. No problem since. I was unaware until this post that those copper rings existed for the gas tank. I believe they are part number 187763, washer, special. I might find some one day but as it's not a concourse car I have found a working solution and until it becomes a problem again I will leave well enough alone.

Len

[mbstude]

I'll offer something just because it may help someone.. After this many years, a lot of times the "wood screws" holding the sender in no longer do a good enough job of keeping things tight (the hole wears out, etc). A mechanic friend came up with a solution a few years ago after getting fed up with one that he couldn't get to seal. After this fix it hasn't leaked again and he's since done it to probably a dozen other cars.

What he does is drill the screw holes out (after removing the tank and filling it with water), tap them, run little bolts through the holes from the inside out (tricky but doable), slip the gasket and sender over the bolts now sticking up out of the tank, and cranking it all down tight with nuts and lock washers. All of the threads are coated with a sealer.

A little more involved than doing it through the hole in the trunk floor, but these cars are WAY beyond their expected service life and sometimes you gotta do what you gotta do..

[TWChamp]

MB, that sounds like a good solution that wouldn't wear out again.

[kmul]

Don't forget to disconnect the battery while working with sending unit,you don't want a spark

causing a explosion or fire SAFETY FIRST !

[mbstude]

I'll offer something just because it may help someone.. After this many years, a lot of times the "wood screws" holding the sender in no longer do a good enough job of keeping things tight (the hole wears out, etc). A mechanic friend came up with a solution a few years ago after getting fed up with one that he couldn't get to seal. After this fix it hasn't leaked again and he's since done it to probably a dozen other cars.

What he does is drill the screw holes out (after removing the tank and filling it with water), tap them, run little bolts through the holes from the inside out (tricky but doable), slip the gasket and sender over the bolts now sticking up out of the tank, and cranking it all down tight with nuts and lock washers. All of the threads are coated with a sealer.

A little more involved than doing it through the hole in the trunk floor, but these cars are WAY beyond their expected service life and sometimes you gotta do what you gotta do..

I received an email after I posted this from my friend that I mentioned.. So to add a little more info...

"Saw where you mentioned the gas tank sender 'fix'. Some things you might want to add...

The repop senders don't have enough 'meat' around the holes to properly take the 'wood screws' and aftermarket seal washers. The washers you get from SI are flat copper and not the original copper asbestos seal rings. Those are NLA. I seal the threads on the bolts or studs with loctite and let it cure overnight. That stuff is impervious to gas when cured. Also need to open up the sender holes a tad for the new studs/bolts. I have seen many tanks that have had various screws (machine and 'wood') shoved in the holes in an effort to fix the leaks. Some tanks need the surface where the sender sits 'adjusted' as previous boneheads over tighten everything and warp the opening in an effort to get them to seal..."

[rockinhawk]

Another possible sorce of the leak could be the rubber hose connecting the filler tube to the tank. I had those go bad on a Lark and a Silverhawk