One other thought...are those metric threads? Are the threads on either the tank or the bolts stripped?

yeah Im pretty sure they are metric (Germany) I did replace one with a larger bolt type machined screw, I think Im going to try that with the one that is leaking.

Yup check for any surface imperfections on the tank and check all the threads on the tank and bolts. Then what I do is use lock tight on the bolts. DO NOT use the red stuff. I think it is green that is the lowest holding strength, blue is probably ok as well. This will not only help to seal up the threads a little but also keep the galvanic corrosion from happening btwn your bolts and tank. Hope that helps

Jon

thats a good idea Jon thanks