Leaking gas tank seal

I have a 99 Cobra convertible and recently had the check engine light come on. Ends up there was a leak in the fuel system. That leak is coming from the donut-style rubber gasket on the side of the fuel tank where the filler neck goes in.

The filler neck goes in about 3/4 of the way up the right side of the gas tank. Which means if it leaks, and you have more than half a tank of gas, you have the potential to have gas leaking out of your tank and onto the right rear exhaust.

The dealer wanted about $700 to fix it. They already greased me for $1,200 to do the 90,000 mile service and replace the plugs and wires, so I bought the $20 gasket and I am in the process of (trying) fixing it now.

Once in a while I did smell gas, but thought I might just be running a little rich or had a dirty air filter or something. So if you smell gas, check this location. It appears that it had been leaking for quite a while before it finally set off the check engine light.

My suspicion is that every Mustang with this style of gas tank and seal will eventually need the seal replaced. Please keep it in mind, and consider carrying a fire extinguisher. :nice:
 
Had a 97 Cobra...but that seal has a bigger opening than the 99+ Mustangs. It leaked on a full tank...replaced it no problem. I have a 01 gas tank in my 81 notchback I am doing a mod swap on...seal was ripped I replaced it.

Just be careful not to break the roll over cut off valve. It is connected to the fuel neck and I broke mine off in the tank on the 01 GT...I dropped the tank, got it out, but now have to fuel rollover valve. Oh well.
 
Just replaced one on my '01 Cobra with 91K miles. It took about 45 minutes. Remove the 3 screws from inside the filler door, loosen the tank straps (make certain the tank is plenty low on fuel), lower the tank and push the filler neck up and out of the tank. The rollover shutoff valve (as stated above) is at the end of the tube, so you'll know you're close when you can see that. Once it's clear of the tank, it's pretty simple to remove, replace and hook back up. Good luck.