There is no bleeder on master. Should or may be two on the Hydrobooster you found. This is not a seperate system, all fluids go thru all the parts. Be VERY careful when trying to loosen the bleeders on the Hydroboost, don't want to snap off. Best to use hex socket, go slow, loosen some, tighten back up, loosen little more, back and forth till comes out easy. Also, the rear wheels will probly have two cylinders in them, may need to bleed both.
I would check for a leaking metal line or wheel cylinder leaking before messing with MC. Setting around is bad on brake systems, specially if in tall grass area.
