968 Fuel Tank Leak Update - Hopeful Fix
04-16-2014, 08:47 PM
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968 Fuel Tank Leak Update - Hopeful Fix
I thought I’d give an update on the leak in my ’95 968’s fuel tank. After a lot of searching and spilled fuel, I was able to locate the leak and I’m surprised it’s not a more common problem.
In any event, what has happened to my fuel tank is this. A flex hose from the external filler neck is what connects the external filler neck to the fuel tank itself. The fuel tank has a neck that is about 3 inches long that sticks out from the tank itself. I have a 1.5” crack at the very base of the fuel tank neck where it connects to the tank itself. The tank body is remarkably soft to the touch and it appears that over time (since 1995) the tank neck has flexed toward and away from the tank and “plastic fatigue” has caused this crack. The tank is FAR more flexible than the connecting flex hose and when I press on the tank or move the hose, the tank flexes right where the crack is.
My problem has been trying to find something that will bond to the plastic tank and be a barrier to fuel. 3M has the only product I could find that is supposed to work. It’s called DP8005 and while the cost of the 2 part adhesive is cheap at about $35, the gun to apply it with the required tip makes the total about $150. It is due to arrive today and I will post photos of the crack and hopeful repair in the hopes it helps someone else in the future with their 968. It will be unseasonably cold here for a day or so, so the repair may have to wait until this weekend.
Fingers crossed!
In any event, what has happened to my fuel tank is this. A flex hose from the external filler neck is what connects the external filler neck to the fuel tank itself. The fuel tank has a neck that is about 3 inches long that sticks out from the tank itself. I have a 1.5” crack at the very base of the fuel tank neck where it connects to the tank itself. The tank body is remarkably soft to the touch and it appears that over time (since 1995) the tank neck has flexed toward and away from the tank and “plastic fatigue” has caused this crack. The tank is FAR more flexible than the connecting flex hose and when I press on the tank or move the hose, the tank flexes right where the crack is.
My problem has been trying to find something that will bond to the plastic tank and be a barrier to fuel. 3M has the only product I could find that is supposed to work. It’s called DP8005 and while the cost of the 2 part adhesive is cheap at about $35, the gun to apply it with the required tip makes the total about $150. It is due to arrive today and I will post photos of the crack and hopeful repair in the hopes it helps someone else in the future with their 968. It will be unseasonably cold here for a day or so, so the repair may have to wait until this weekend.
Fingers crossed!
04-26-2014, 01:27 PM
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Hopefully this helps someone in the future. If anyone has questions just let me know. My car developed a wicked raw gas smell. Any time a window or the sunroof was opened beyond a crack it was awful. A lot of searching revealed a think crack in my coupe's fuel filler neck right where it exits the tank itself. I've put a few pictures here to give a decent view. The red arrows point to the crack but isn't really seen in the photo. The leak found, the next problem was how to repair it. The fuel tank is made of polyethylene which has one massive inherent problem. Almost nothing except polyethylene itself will stick to it! My first thought was to rough the area up with sandpaper and pour some melted polyethylene onto the crack and surrounding area. But that would mean draining and flushing the tank and that means removing it. Right now I can't afford the cost of removing the tank and if I did remove it, I would just replace it. A call to 3M revealed a product called DP8005. It's one of the only epoxies that will adhere to polyethylene. It's actually a structural adhesive. Finding a place that will sell individual tubes wasn't easy but in the end you have to buy the DP8005 in a 35ml 2 part cartridge, a gun to use the cartridge, a 10:1 plunger and a mixing nozzle. I had to buy a 12 pack of the nozzles. Total was about $160
According to 3M no prep of the area beyond removing grease and dirt is necessary and the 2 part epoxy has a 3 minutes time frame for use once mixed. Since the plastic was cracked, the first think I did was use a sharp point to make relief holes at either end of the crack. I used a test light probe. I scuffed the area with sandpaper (even though the instructions didn't say it was necessary) and cleaned it with brake cleaner. The instructions were simple. The mixture swirls around in the mixing nozzle and came out a bit more liquid than I had hoped. I went around the entire base of the filler neck slowly. I tried to be careful not to get any on the body of the neck where I would have to replace the filler rubber flex hose. Full curing time is 24 hours.
Once cured, the adhesive had a sort of micro bubble appearance. My fear was that while it might be a strong bond, it might not be air tight and still allow gas vapor to escape. The greatest surprise was when I removed the mixing nozzle and fitted a new one. It STILL worked! The seal from the nozzle to the cartridge was so good that the epoxy parts in the cartridge didn't dry out! So, I made a second pass over the first application. The next day I was able to do the same thing making a total of 3 applications. And to think I was angry at having to buy 12 nozzles!!!
Well it's been 3 days since the 3rd application fully cured and knock on wood it's sealed and no gas smell even with both windows wide open. As an aside, I have also decided that to keep the old hoses and anything further happening to the tank, I'm making it a habit of cracking open the fuel filler cap after each decent drive of 50 miles of more to relieve the strong vacuum created in the system. I think that going from full down to a quarter of a tank puts a tremendous vacuum strain on these parts that have been doing their job since 1995 on my car.
Pic 1 shows the filler hose still attached and I'm pointing to the crack
Pic 2 has poorly drawn red arrows showing[IMG][IMG]
[/IMG][/IMG][/IMG] the length of the crack, about 1.5". The hose is removed and I have painters tape over the opening.
Pic 3 shows the finished seal after 3 applications from the single 35ml cartridge.
Hope this helps.
Ron B.
According to 3M no prep of the area beyond removing grease and dirt is necessary and the 2 part epoxy has a 3 minutes time frame for use once mixed. Since the plastic was cracked, the first think I did was use a sharp point to make relief holes at either end of the crack. I used a test light probe. I scuffed the area with sandpaper (even though the instructions didn't say it was necessary) and cleaned it with brake cleaner. The instructions were simple. The mixture swirls around in the mixing nozzle and came out a bit more liquid than I had hoped. I went around the entire base of the filler neck slowly. I tried to be careful not to get any on the body of the neck where I would have to replace the filler rubber flex hose. Full curing time is 24 hours.
Once cured, the adhesive had a sort of micro bubble appearance. My fear was that while it might be a strong bond, it might not be air tight and still allow gas vapor to escape. The greatest surprise was when I removed the mixing nozzle and fitted a new one. It STILL worked! The seal from the nozzle to the cartridge was so good that the epoxy parts in the cartridge didn't dry out! So, I made a second pass over the first application. The next day I was able to do the same thing making a total of 3 applications. And to think I was angry at having to buy 12 nozzles!!!
Well it's been 3 days since the 3rd application fully cured and knock on wood it's sealed and no gas smell even with both windows wide open. As an aside, I have also decided that to keep the old hoses and anything further happening to the tank, I'm making it a habit of cracking open the fuel filler cap after each decent drive of 50 miles of more to relieve the strong vacuum created in the system. I think that going from full down to a quarter of a tank puts a tremendous vacuum strain on these parts that have been doing their job since 1995 on my car.
Pic 1 shows the filler hose still attached and I'm pointing to the crack
Pic 2 has poorly drawn red arrows showing[IMG][IMG]
[/IMG][/IMG][/IMG] the length of the crack, about 1.5". The hose is removed and I have painters tape over the opening.Pic 3 shows the finished seal after 3 applications from the single 35ml cartridge.
Hope this helps.
Ron B.
04-26-2014, 01:28 PM
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04-26-2014, 01:29 PM
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04-26-2014, 01:29 PM
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04-29-2014, 05:49 PM
#8
Don't think you should pull a vacuum on the tank. The emissions system should remove the excess vapors of a properly operating system.
I have 2 968's and a 951 and have never had any indication of a vacuum on any of them.
I have 2 968's and a 951 and have never had any indication of a vacuum on any of them.
04-29-2014, 06:04 PM
#9
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Ron: This is interesting, I too had a strong fuel smell and replaced the sending unit gasket, it solved about 95% of the problem. Last week when it started getting warmer out, and after a long drive, I could get a hint of fuel smell. Wonder if I have the same issue.
10-15-2017, 11:30 PM
#11
Hello,
At the track this weekend I did fill up and when I returned and parked for a while, I noticed a good dripping of fuel coming from passenger rear (right where the fuel tank is!). Looking from underneath, it looked like it was coming from higher up and I suspect it was the same issue as described here. I have a 95' 968 and sitting in garage now with 1/2 tank, no leak. I haven't ever seen this issue until this weekend. However I do notice a fuel smell in the garage.
My question is, how do you approach to look at filler neck? If you go the 'in trunk' route, do you just rip away all the glued carpets? Also there is the rear seatbelt in the way which looks like a PITA to remove. If you go from underneath, can you even do that without removing fuel tank and other items?
Any help here is appreciated as I start to investigate this.
At the track this weekend I did fill up and when I returned and parked for a while, I noticed a good dripping of fuel coming from passenger rear (right where the fuel tank is!). Looking from underneath, it looked like it was coming from higher up and I suspect it was the same issue as described here. I have a 95' 968 and sitting in garage now with 1/2 tank, no leak. I haven't ever seen this issue until this weekend. However I do notice a fuel smell in the garage.
My question is, how do you approach to look at filler neck? If you go the 'in trunk' route, do you just rip away all the glued carpets? Also there is the rear seatbelt in the way which looks like a PITA to remove. If you go from underneath, can you even do that without removing fuel tank and other items?
Any help here is appreciated as I start to investigate this.