Dansk fuel tank leak

ThomasB · 08-10-2012, 12:53 PM

I recently installed a new 65L tank into my 1970 911E because the old one was very rusty. The new tank is a Dansk.
I also replaced the fittings because the PO seems to have cut off the small filtering net on the inside of it. Of course I also renewed all gaskets.

Unfortunately I have a fuel leak at the gaskets/fittings (4) and (6) in the picture. It was noticeable after first filling the tank and letting the car stand overnight.

I then tightened both of the fittings VERY tight and the leaks are now less but still there. About 5 ml over night, barely a few drops, but thats 5 ml too much for me before the cover goes back on.

So I took the tank out again today and really want those leaks gone when I put the tank back in. Would it be advisable to use aluminium crush washers here?

I have a few oil tank crush washers left, they seem to fit the diameter of those fittings.

DW SD · 08-10-2012, 01:27 PM

1. Yes, I would try AL.
2. You also could use some form or sealant on both sides of the washer. I'd use something very high quality and suitable for fuel, of course.
3. I've successfully used washers from Earl's which have AL and a rubber o-ring seal in crush washer (fuel, too) applications.

Doug

ThomasB · 08-10-2012, 01:32 PM

Quote:

Originally Posted by DW SD

1. Yes, I would try AL.
2. You also could use some form or sealant on both sides of the washer. I'd use something very high quality and suitable for fuel, of course.
3. I've successfully used washers from Earl's which have AL and a rubber o-ring seal in crush washer (fuel, too) applications.

Doug

Thank you. I have ordered some Loctite 577 which won’t arrive until monday. It is an anaerobic pipe thread sealant and 100% gasoline resistant.
I’ll put it that on the threads and use the AL washers. I hope that solves it.

DW SD · 08-10-2012, 01:38 PM

Glad to help. I'd try with AL and see what happens in the meantime. These shouldn't seal on the threads themselves. They should seal on the flat surfaces vs. the metal crush washer. I'm not sure thread sealer is the right product. I'd use something like guys are using to seal the engine case-halves together and only use it on the flat surfaces.

Did you debur the sealing surfaces? I'd try that, too. Carefully run a fine flat file (or 320 grit wrapped around a flat bar stock) SQUARELY across the sealing surfaces on the tank.

Doug

RSTarga · 08-10-2012, 02:07 PM

I can't recall but i think fibretight seals work better with fuel. I wouldn't bother with any sealing compounds on the threads.

steve911T · 08-11-2012, 05:00 AM

I had the same problem when R and R of my fuel tank on my 70T. I did not have to use any sealant, just a breaker bar where I could and torqued the heck out of it. The leaking stopped. In the old tank, they have a plug with a large metric allen that really needed lots of torque to stop the fuel from seeping. Good luck. Steve

ThomasB · 07:03 AM

I now tried the red fiber-plastic (is that fibretight?) seals, AL and CU washers. All of them leak. I let my mechanic put on the CU ones because I thought I must be making some stupid mistake but nope, same result.
We also sanded/deburred the sealing surfaces the best we could and with the tank positioned overhead so no debris could fall into it, unfortunately that didn't help either.

Mind you, it leaks just minuscule amounts but a fuel leak is a fuel leak to me, even if it is just a single drop every 24 hours.

I’ll try again on monday with LOTS of torque and the fuel resistant Loctite 577 which seems to be made for these applications.

porwolf · 08-11-2012, 05:27 PM

Could it be that the entry and exid threaded bases are warped? If so, it would be hard to get any washer to seal properly. Happened to me once on the oil pan on my landcruiser. But the specialty shop had experience with that situation and was able to flatten out the spout which fixed the problem. What about using RTV silicone in addition to aluminum washers for your gas tank?

Nancy C · 06-06-2014, 05:48 AM

I know this is an older thread, but can you tell me about your experience with the Dansk replacement tank? Was it a good fit, or did it require modifications to fit your car? Were you able to resolve your leak around the fittings? Thanks.

sebastianroher · 03-09-2015, 01:28 PM

Quote:

Originally Posted by nancy c

i know this is an older thread, but can you tell me about your experience with the dansk replacement tank? Was it a good fit, or did it require modifications to fit your car? Were you able to resolve your leak around the fittings? Thanks.

+1