Leaking 1974 gas tank

[z4life92]

Hey everyone I have a 260z and the gas tank leaks if I fill it up past half tank. I changed the sending unit and I changed the oring and lock twice but it still leaks! I watched it leak from the unit so I know for a fact It comes from there. Also I capped off all the unnecessary vents. So my question is WHAT THE HECK IS WRONG WITH MY TANK?? And if i do infact need a new tank where might I find one for cheap preferably used as I dont have much cash like the typical college student. anyways HELP PLEASE!

[beermanpete]

If the fuel is leaking past the o-ring then the tank or sender unit might be bent or have a small flaw in the sealing surface such as a scratch or pitting due to rust. Inspect the surface carefully for any irregularity.

The sender unit has a feed-thru for the wire. Perhaps it is leaking at the feed-thru.

[BTF/PTM]

Seam leak?

It's a sloppy way to troubleshoot, but if it is a seam leak and it's anything faster than a slow drip you should be able to fill the tank a little past half way and spot it with a flashlight. Wipe the tank down first and you'll see the source of the leak when the light hits the fluid.

The above mentioned check of the level sender sealing surface is a good idea, too. Again, if the leak is from there, you'll see it with a flashlight.

As a final note, it may be a good idea to take the tank out of the car at this point. Pain in the arse, but you'll have a full view of every angle of the tank and you can use a very small amount of gasoline and just roll the tank around as needed. Or, you could just take this opportunity to replace the tank with another one *shrug*

[Powderkeg]

I don't think the gas tank has any "unnecessary vents". I could be wrong though.

Look into getting the POR-15 tank coating system.
Also search on this site for removing the gas tank. It's not that difficult.

Good luck.

Dave Ruiz

[olzed]

Are you sure it's not a leak from the filler hose?