what happens if i dont bench bleed the master cylinder? Will the air in the master cyl bleed out of the brake lines when i bleed those or is it mandatory i bleed the mc?

 

You should always bench bleed the master cylinder before installing it.

 

The master cylinder , when mounted in the truck , is positioned at an angle that traps an air bubble.
The air bubble will NOT come out with conventional bleeding.
Turn a half empty soda pop bottle upside down. How would you get more liquid in the bottle and all the air out with it in that position ?

 

Thanks