Can gas leak by a new sending unit gasket and then seal itself?

[Zymurgy]

Ok here is the situation I have never filled the tank past half because it would leak from the sending unit. After nearly 2 years I discovered that I had the rubber gasket between the locking ring and sending unit not the tank (wasn't going to admit this).

I had nearly a full tank yesterday, no leaks and drove it nearly 200 miles. I filled it full today and it was leaking once again, I presume from the sending unit. Once I got it home (7 miles) it smelled of gas but no leak. The gas, in the tank, is still above the sending unit gasket.

My question does the gas actually expand the rubber gasket and make it seal better? When I re-installed it correctly there was nothing wrong with the gasket still pliable and flat.

 

[ceebuddy]

Happened to me, too. Installed the gasket correctly afterwards and then it was all tight.

 

[tallhair]

Expansion could be forcing gas and or fumes out the vent tube or more fumes than normal or otherwise pressurizing the tank and causing the leak where ever it can get out and causing you to smell fumes with or without a leak.

When cool and or not a full tank no leak no fumes smell?

Gas cap seal in good condition? Should be a non-vented cap

Is vent routed properly/exit higher than the tank w/ no holes or breaks?

 

[Zymurgy]

My vent tubes were the next thing I was going to examine more closely. They are routed correctly but still have the original rubber sections. The rubber sections may be the problem. They also have no clamps is this correct?

 

[tallhair]

I don't know what is 'correct' but the ones I've worked on had clamps. The tubes should be flanged if I recall which will help seal but I'm almost positive my RR had spring clamps on those hoses the first time I removed it and I definitely had them on when I put it back .. I never removed a C body tank.

Also make sure the vents are not blocked when you check them .. they are to let air in when the car is running/driving to prevent vacuum collapsing the tank

However a full tank warm gas can cause it to pressure up when you shut the car off and gas can escape through them or siphon out if they are too low

 

[BIGBARNEYCARS]

Mike, To my knowledge I don't think any of the manufacturers ever used clamps on the vent tubes. It's only there for venting pressure vapors, that's why its way up top side. Any signs of leaking at the filler tube or the rubber grommet there? Also a possibility that the draw tube where it goes thru' the sending unit collar has the soldered seal cracked. Bought an A-100 pickup yearz ago that had that issue and the previous owner tried to repair with tub-'n-tile calk. The first fill up I had gas everywhere. Easy fix once you drop the tank and remove it to re-solder but what ah pita. BTW, Last time I checked you could still buy the ground strap from Mother Mopar for bridging the rubber connecting piece for the steel gas line where it connects to the draw tube nipple on the sending unit if you need one? Good Luck with the fix where ever you find it. Keep us posted, Jer

 

[detmatt]

I just inspected the vents on Silver and I don't think they had the original rubber but they didn't have clamps and now they have new rubber and clamps.

Morning Jer! I just bought new the strap that Jer mentioned from Dave at Roseville Moparts. He has them in stock both short and long.

 

[commando1]

Every connection, I believe, had at least one of these:

 

[tallhair]

Those are the ones I was talking about Stan.

 

[65sporty]

My question does the gas actually expand the rubber gasket and make it seal better? When I re-installed it correctly there was nothing wrong with the gasket still pliable and flat.[/QUOTE]

Gas will make it expand but not in a good way, the sender was leaking on the 65 when I removed it for repair the seal was expanded and misshapen twice it's normal size. I repaired the sender picked up a new lock ring and seal, the sender fits tighter now no leak. when it is installed only a small portion of seal contacts fuel

 

[Zymurgy]

Thanks guys it might be sending unit seal and lock. It came out too strong of a pour last time I filled it up for it to be through the vent I believe. However, I can replace the vent rubber lines and install clamps first pretty cheaply.

 

[thrashingcows]

Check your gas cap. I know on the wagon I have to install it only one way, or it will vent fumes. Took me quite a while to figure this out. Not sure why it does this, but it does. I put an arrow on the gas cap with a sharpie, pointing up, so I know what direction to install it.

 

[Zymurgy]

Check your gas cap. I know on the wagon I have to install it only one way, or it will vent fumes. Took me quite a while to figure this out. Not sure why it does this, but it does. I put an arrow on the gas cap with a sharpie, pointing up, so I know what direction to install it.

Thanks for the tip, I will replace that too. I just checked it out and there are cracks in the gasket. I think the gas leak may be the vent lines after all. I crawled under the car between football games and the rubber line were not seated where they should have been.

I ran and bought some clamps, the rubber lines had been replaced, I just forgot I had replaced them. I'll let her cool down put on the clamps, go fill her up and keep my fingers crossed.

 

[moonrunner1972]

Zymurgy,

I had this exact same problem when I removed the sending unit from my 73' Polara. After I replaced the sending unit, I could not get the locking ring to seat properly. My wife was panic stricken when about 5 gallons of gas dripped on the garage floor. I had to syphon about 10 gallons out of the tank for it to fall below the sending unit for the leak to stop. Part of my problem was that I was lying on my back trying to use a drop light to see if the notches were properly aligned. I foolishly purchased the special wrench used to remove and replace the locking ring under the assumption that it would cure my problem. It was only after I put the car on the lift that I was able to see the problem. A flat tipped screwdriver and ball peen hammer were the only tools I needed to stop the leak. While you probably already checked this, it may be worth a second look. Good luck!

 

[Zymurgy]

Zymurgy,

I had this exact same problem when I removed the sending unit from my 73' Polara. After I replaced the sending unit, I could not get the locking ring to seat properly. My wife was panic stricken when about 5 gallons of gas dripped on the garage floor. I had to syphon about 10 gallons out of the tank for it to fall below the sending unit for the leak to stop. Part of my problem was that I was lying on my back trying to use a drop light to see if the notches were properly aligned. I foolishly purchased the special wrench used to remove and replace the locking ring under the assumption that it would cure my problem. It was only after I put the car on the lift that I was able to see the problem. A flat tipped screwdriver and ball peen hammer were the only tools I needed to stop the leak. While you probably already checked this, it may be worth a second look. Good luck!

Thanks for the tip. That is pretty much where my problem was. I seem to be in go shape now, but I haven't filled the tank more than 2/3ths full either. I was having problems when I was 3/4ths or more.