Finding fuel tank leak

[EdW]

Last couple of fill up's in my 98 Corolla, could really smell gas outside the car until the level got below about a half on the gauge. Slid under and took a look at the tank, at first thought it may be the small section of rubber breather hose next to the mail fill line from the fuel neck that connects the small vent tube to the tank. But after looking again on the next fill up's, it seems the top of the tank may be the source, judging from the "stains" so to speak, as they seem to be coming from the top of the tank and down the rear top side.

So I'm wondering if there's a chance the issue could be one of the three round seals on the top of the tank (Fuel pump assy seal, check valve assy seal, or the cutoff valve assy)?

It looks like dropping the tank is a bit involved, and chances are the straps are rusty and going to be shot on removal, so it would be great to be able to determine what's going on before dropping it. Especially if I need a new tank... also hate to buy a new one if it is a seal or hose.

Just had a thought, is there an access plate under the back seat bottom I could use to take a look at the top of the tank?

Thanks in advance for any suggestions.

Here's a link to the tank diagram:

http://www.utoyot8.com/FullImage.asp...-++(9708-++++)

[Bennie]

There is an access cover under the rear seat.

[Milky]

^^^ yup, there is one. it is sealed up with some black goop, dont know what else to call it really, but use a flat head screwdriver or prybar and slowly work around the cover, prying up as you go. it will pop off.

[EdW]

Thanks for the replies. I'll take the seat out tomorrow and have a look.

This has been a great car and "only" has 100k on it, but in the last year plus it feels like it's getting eaten by the rust monster. So far a rear strut, 2 brake lines, the evap VSV, the exhaust, and now possibly the gas tank have all failed from rust. Am hoping the tank is just a seal but I think that's optimistic.

[Bennie]

EdW, That brings up a good question. Do these things even have metal tanks? It wouldn't surprise me at all if they are plastic but I don't have any idea. Anybody know?

Sounds like your car has really taken a beating from rust. I live in MN and we're know for salty roads and my car is pretty clean. I've had to patch a couple spots in front of the rear tires and in the spare tire well but I've got a lot of miles on my car so it's pretty expected.

[EdW]

Finally got around to taking a look, tank is metal for sure. Pulled that access cover under the rear seat, but the tank is up so close to the underbody, there's really no space to be able to look around unfortunately. Even trying to look from the upper edges with a flashlight and mirror was difficult and I couldn't see much.

Also realized that the exhaust runs right under the righ 1/3 of the tank, so I'd have to drop that first to get the tank down. It's a bit rusty and "delicate" looking, so disturbing it may be trouble.

Have one more idea, using my compressor to put some low pressure air into the fuel neck and spraying the sides and seams of the tank with soapy water to see if I get any bubbling?

Then again, with gas going through the roof, I may not be able to afford more than 3-4 gallons at a time, so I may just end up living with it as is!

[1998rolla]

there are products that can seal pin holes in tanks but im not sure if they work when the tank has rust on it and to apply the product the tank needs to come off. from the sounds of it fixing a leak this way isnt going to work for you but i figured i would let you know

[EdW]

Thanks for the info, that was my first plan, depending on where the leak was. I used it once in the past with good luck and would definitely give it a try again. That tank was rusty but I cleaned it up and the product adhered well. But the leak was visible and fairly easily accessable too...