It's a brake line. There are three lines coming out of the proportioning valve - 1 line runs to the rear brakes (gets different pressure levels) and the other two run to the fronts, 1 to each side.

 

no, i didnt circle the brake line, ill see if i can get another angle

its a sort of a black plastic nipple coming off the back of the whole assembly.

 

 

"Oh - I see" said the blind man!

Um, I don't know what it is - it's like a rubber or plastic cap right? All of them have it. That's one of those things (in my world) where if it ain't broke, I don't mess with it LOL.

I believe I've seen articles on here that describe removing it, and maybe a screw behind it, and drilling out inside there, replacing the screw (maybe a longer one or something) and getting different line pressure for brakes - for whatever reason. Maybe try a search on proportioning valve mods, or check the tech section for an article - I know I saw something on here about it.

 

under that black rubber thingy is a place where you can unscrew, i believe, cant remember, to take out the tension spring and a valve to allow certain amounts of brake fluid to the rear and front brakes, i took my apart a couple years ago to adjust for swapping drum to disc brakes.

 

That's the cover to the screw that allows you to remove all the internals of the valve, I don't recommend screwing with it.

Ed