1970 Challenger -
12 month restoration almost over....finishing up brakes.

Everything in my brake system is (brand new) and brakes are bled, holding pressure and working "ok".

In the photo below, the brass distribution on the left (bottom) is leaking from the plug on the bottom of the block (the black thing on the bottom of the block).....but here is the strange part and the big question.

On the bottom of the block, there is something that screws into the block with a small nipple and a rubber seal. THE SMALL NIPPLE can be pushed in like the needle in a tire valve stem...

I can put my finger on the little stem sticking out of the bottom of the brass block and push it up into the block.... When I let go it drops back into place.

This is the area where it is leaking.

Is it normal for a brass block to have this little nipple and be able to push it up into the block like a valve stem ?

Any ideas ?
Mike