Bob_Spidell
Yoda

Online
Bob Have you tried making a cork gasket?. I was having great difficulty with mine as it looks to be a hand built tank and they did not reinforce the bolt area, just used self tappers to hold the sender in on a rubber gasket. I could not get a seal so I reverted to the installation of a 'bolt in' washer style plate (inside the tank) in two halves containing six rivnuts to line up with the self tapper holes and tried that with a rubber gasket and M5 bolts- no good, so in the end I made a good old cork gasket and that has sorted the problem out, as I could get a reasonable torque on the bolts.
Bob
Thanks for the tip, Bob. Yes, I've tried cork and two types of rubber (silicone?) gaskets, with and without fuel-resistant sealant. No luck, although my test has been to fill the tank to the bottom of the filler neck which might be a bit extreme.
I'll have the car at my house soon so I can fiddle with it some more. Do you know what the thread TPI is?