I have a slow leak coming from what appears to be the passenger side gas tank strap on my '87 GTA. The leak drips down onto the heat shield and slowly works it way to the driver's side, then drips off the shield to the ground. I did my best to inspect the line(s) going in at the top of the tank. I didn't see any leaks from any of the rubber lines where they connect to the metal lines going to the tank. I did my best to take some decent pics..

Image #1 below is the tank strap area on the driver's side:



Image #2 below is the passengers side. Notice the black gasket is shiny and the tank appears to be dry on the other side of the gasket. When I pushed up on the metal strap, the gasket oozed gas. The small clean strip in the blackish leak area is where I used my finder to rub the tank to confirm it was wet.



My working hypothesis is that the gasket has become misaligned over the years (the tank is original) and tank strap has been rubbing directly on the tank to the point it perforated it. Any thoughts or advice?

 

Get to work. You've got a tank that needs to be emptied and removed so a fuel leak can be fixed.

 

Your diagnosis may be correct. Or it may have rusted through in that area. Either way, QwkTrip is not wrong!

 

Okay... work, I shall do. What are the pros and cons of repairing the tank vs replacing? Aside from cost, obviously.

 

Well, the two sides are this;

If it's rusty/rotted from the inside causing the leak, then yeah replacement is really the only way to go . A pinhole leak in an otherwise clean tank would of course be fixable.

New tanks can be a mixed blessing indeed, yeah they are new, but there are lots of reports of aftermarket tanks fitting badly, especially WRT the filler pipe .

 

FWIW, I bought a replacement tank around 2014 (the filler neck was mangled on my original tank) and the quality left a lot to be desired. The filler neck on the new tank technically fits through the little plastic insert behind the fuel door, but it rubs more than I'd like. I also had to do a little work to get the fuel pump mounting ring (not sure of the proper term) to fit - just a few minutes with a screwdriver and some pliers, but still disappointing for a "factory replacement" tank. Then had to try several gas caps before I found one which fit properly.

Of course a replacement might be the only way to go.

 

It could be leaking any where, and of course running down hill. To find those pesky, mystery leaks, i use talcum powder. Clean everything best you can, then sprinkle powder every where. Turn the key on, or start it,...it will become more obvious where the actual leak is coming from. A small mirror and flashlight can be very helpful. I've used this method to find many mystery leaks over the years and it works good.

 

That's good advice, I will do this. I watched a Youtube video on how to remove the tank. Looks like a PITA....

If I could possibly find the source of the leak without removing the tank, that would be a major schwing. But knowing my luck, the whole damn thing will have to come out...

 

You can do it in a days time, no problem. Put it up on stands at the frame as high as you can, unbolt and drop your stuff down (watch your brake line!). You will probably need new end links, so get them ahead of time. It can be done with the stock muffler just dropped laying on the axle. It is not that bad, hardest part I would say is to just get motivated and start. The leak is most likely coming from the top and working its way down the straps anyway. Poking around is just wasting time. Do what QwkTrip said and this will be a distant memory.

 

It is common for gas tanks to rust out under the straps. The rubber cushions hold moisture, which over time take a toll.

There are gas tank epoxies that can be used for repair. I'm not saying that it is a great idea or a fail. But is one fix to consider.

Another solution is to use a plastic 4th gen gas tank. Not easy, but can be done.

RBob.

 

My car is one that has seen very little moisture over the years. No rust at all anywhere on the vehicle. And I live in Colorado, so even if and when it does get wet it dries quickly. But the cushions are original, so I would replace them. Can this be done without removing the entire tank?

 

Could the leak be possibly coming from the top of the tank at the fuel pump locking ring? Is it common for that rubber seal to go bad? I know mine is original from 1987

 

About the only way fuel would leak from the tank top unit O-ring seal is if the tank is overfilled, or of the pressure or return lines were leaking/spraying directly against that seal. Even then, the O-ring (or tank metal) would have to be dereriorated to allow a leak.

More likely the lines themselves have problems if the leak is from the top area.

 

I found the leak: I have a very small hairline crack about 1 inch from the strap. The crack is maybe 1/4 inch that runs across (perpendicular) along the edge of the tank mold line. Working now to patch it. I'll post a picture asap.