If it were my truck I would remove the second line back to the master cylinder and plug the second outlet on the booster output, and see how the brakes function, hope that helps.
If I am unable to locate part numbers for the master, it very well could be the only option. Any idea if these master's have a part or serial number stamped on it anywhere? I am yet to find any solid info on the operational difference between the 11" and 12.75" hydro-vac systems. I wont lie, I like the idea of more brakes, its never a bad thing especially as this girl will load heavy.
If you are going to keep the two line MC and can't find a replacement...just send it out and have it sleeved and a new kit installed.
I am looking into this possibility currently.
If you refer to the original image, you can see the discoloration and rust in the master area of the firewall. Whatever seal used to be on the master cap is long since gone, and that return line puts some serious pressure back into the master clearly as it shoots it everywhere on the firewall as well without that seal. This was the main reason for replacement.
To be clear, both the master and hydro-vac still function fine, but the significant corrosion means limited life. With the engine out I figured its best to refresh everything as I have to do the brake lines regardless. Ill work with Napa again tomorrow on these items and report back with what I find.
Somewhat related topic, is there a master list parts book for these trucks somewhere? None of the factory manuals carry part numbers, and its killing the efficiency of finding parts and cross referencing part numbers. Just curious. Id buy it in a heartbeat.
