Leaking water temp sensor, help please

[RickKlem]

TO30

I posted this question in the wrong area and I was ask to post it here.

I installed a new water temp gauge and the temp sender is dripping. I know there is an issue with some temp sensors being too long , causing the mounting nut not to tighten down, this is not the case. The temp sensor is not bottoming out on the back side.

I have tightened down on the nut as much as I can, but it still leaks.
Can I use a sealer or silicon around the sender to help seal it?

Thanks
Rick

 

[714_run]

take a lock washer twist it open put around the tube twist it back flat tighen the nut against it

 

[J.Wondergem]

Does the nut have a hair line crack?

 

[Tom Bowman]

Rick, I used thread seal tape on mine.
And, like J. Wondergem suggested, check for a crack in the fitting, which I had. (Photo attached.)
In addition, I think a previous owner had done some creative plumbing to attach the sensor to the gooseneck, and messed up the threads. I finally found an adapter kit that included a fitting that worked. (Other photo attached.)
My gauge works, and doesn't leak, but I sure ain't gonna mess with it again!