MASTER CYLINDER PROBLEMIhave

[69Chevelle L78Deluxe300]

I spent about 50 hours trying to bleed the rebuilt master in my 69 chevelle with silicone and everyone told me the problem was silicone fluid. What I finally figured out was the original proportioning valve located below the master cylinder was sucking in air when I released the pedal but not leaking fluid out when I depressed the pedal . I put a new one on and had no problem bleeding.