I have a 1992 940 Turbo sedan that I bought used in 1998. It has about 140k mi. on it I think, but I am not sure because the odometer/speedometer works intermittantly due to some sort of electrical issue.

When the fuel tank is more than half full or so, fuel leaks down the fore part of the tank, even though all the fittings seem to be aft. Once the fuel level is below about half, the leaking seems to stop. The leaking is slow enough so that the dripping is limited to a brown, smelly gas residue, as opposed to a large amount of obvious gasoline.

Logically, this would appear to indicate a hole or crack in the top portion of the fuel tank, but I have never had it off and don't know the architecture. The Chilton manual I have for this has no drawings or photos of the tank and fittings.

Are there any other leak scenario possibilities that could account for the observed behavior other than a fuel tank with a hole in it? Are there any fittins on the fore section of the tank anywhere?

If any of the experts out there could offer a suggestion, I would be much obliged! Thank you.

I would suggest that you have a split in the seam of the tank. There should be no fittings in the forward end of that tank. In fact all the fittings on that tank should go through the sender with the exception to maybe one nipple that is again in the very rear and it mounted way up on the top like the other fittings so that if it leaked it would only do so on a full tank. You are just going to have to roll under it and take a serious look at it. If you find that it is indeed a crack or split in the tank you probably will have little to no choice but to change out the tank. Depending upon location you can try a JB weld bandaid on it when it is low on fuel and see what that does for it. Those tanks are normally very very tough, I had one in the shop recently that was deformed as part of an accident. I sealed it up tight, applied compressed air to it and heated up the dented area with a hot air gun and it popped right back out and you could not even tell it had been dented.

mark

Well, you were right, it was a 1/2" long split starting at a seam. Unfortunately, the split was at the bottom front seam. Apparently, it leaked imperceptibly unless the tank was more than about 1/4 tank full. When full, it would leave nasty puddles of gas residue. Judging from the location of the leak, I suspect that some sort of road debris impact was the cause.

I looked into repairing the tank and might be able to do so, but found that this seemed to be a problem with insurance companies, so I ordered a new tank. With the new gasket, I will be out about $350 for the new tank.

Thank you for your very valuable advice!

Did you have to go with a new tank? Fuel tanks are one of those things that for the most part are either good or they're not. I do not know what the availibility of bone yards is in your neck of the woods but I'd be willing to bet you could've saved some serious wampum by going that route. Glad to hear you've got it diagnosed though and are in the home stretch on fixing it.

Good Luck,
Mark

My schedule doesn't allow me the time luxury to go through the U-Pull-It boneyards and remove a tank, and junkyards want about half of what a new one costs. I figured for the extra $175 over a used one, a new one would provide the extra confidence level and peace of mind. Thanks.

Fair enough, it is hard to go wrong with a brand new factory part. Some guys thrive on that stuff but while there can be a cost savings involved in boneyards they can also be a pain in the ass and a colossal waist of time.

Mark