First, I've got a 73 c20. It's 8lug, with discs in front, and drums in the rear. I've been at it all day. I bought the truck and knew there was a brake issue but the previous owner didn't know what was wrong. Brake pedal goes all the way to the floor. The first half its easy, then the second half it's hard like I'm doing a leg press. It barely stops.. BARELY
I'm also getting no fluid to the rear brakes.
I've bled brakes (passenger rear, driver rear, passenger driver, front driver) using the two person system. I've done a tube in a bottle until no more bubbles, and borrowed a vacuum bleeder. No change.
I used a master cylinder bleeder kit to bleed it. Ran lines returning to the fluid back to reservoir, and pumped until no more air.
Blocked the master cylinder off and blocked the 2 outlets. Pumped, and built pressure (only time I've got pressure). I opened one outlet, and the pressure escaped. Tried the other outlet, and same.
I disconnected the rear brake line from the proportioning valve. I ran air from the front of that, and went to the rear. No air, no bubbles, nothing, so I'm believing an issue or clog somewhere along the line?
I also ran fluid into the lines I disconnected from master cylinder and fluid runs out of the proportioning valve.
I don't know what more to do. At this point I'm thinking replace master, booster, and lines. I just didn't want to throw money at it if I could find the issue/issues. Thanks for all the help
