[Superannuated Peregrinator]

Good day gurus. I can hear air leaking from behind the rear wheels. Using my leak detector, I tracked it down to the bottom side of the manifold that holds the air dryer filter behind the left rear tag tire. The leak is coming from where the hex head is located in the attached picture. The picture is the bottom of the manifold to which the air dryer filter is located on top. My question is whether I can try tightening the hex bolt or if that is not recommended? If I do tighten it, how hard can I crank down on it?