I have a small leak, looks like this is the transmission cooler line going into the radiator, it leaked about 2 weeks ago, I pulled the bumper, removed the clip, tightened up the nut going into the radiator and everything was fine. Today it started again. Would hate to have to remove the bumper all over again. Any ideas what could be my cause or tips how to fix it?

 

Pull clip again and replace the O-Ring with a new one (green) in color obtain from O-Ring
supplier so it is compatible with transmission oil.....Good Luck, Nitrame