[Tongue Pirate]

Sounds like we have the same guage. If so the correct fitting for the manifold should be taperd in the bottom as to seal the temp sensor between it & the top nut. If you are getting the top nut to bottom out & there is still slop you have the wrong bottom fitting. If the top nut is tight & there is no slop yet it is not sealing up it is possible that your sensor could be bottoming out before the nut can get 100% tight. If you look here you can see my sensor & manifold fitting. It has a 3/8" pipe thread into the manifold.