Brake trouble shooting help

[bhemingson]

I just bought a 1972 Cheyenne Super. 3/4 ton leaf spring truck. 350 automatic. All stock. The owner said the brakes might need bled. What an understatement. I went to pick up the truck after coming home from a trip. Brake light on. Super hard pedal near the floor. Almost no braking capability. Front master cylinder reservoir near empty. Q1: Is that for the rear brakes? Q2: with that front reservoir dry I probably have air in the lines but how do I reset the proportioning valve as I understand it "clicks" over when brake warning light is triggered.

I added brake fluid and after about 20 minutes driving on back roads to my shop I started to get a little pedal (in my head maybe) and the reservoir still had fluid. What is the most logical place to start to get brakes without just throwing parts and time at it?

[geezer#99]

Front is normally for the rear.
Prop valve needs to be reset.
To do that you need to push in and hold in the button at the front of the valve when you bleed the brakes.
Check your rear drums for leaks first.
Likely you have leaky wheel cylinders.

[Stocker]

^^ What he said.

Sometimes you can reset the prop. valve by pressing very hard on the brake pedal.

[bhemingson]

Thanks guys that's exactly what I need to get started. Appreciate the help.

[demian5]

Almost sounds like a bad master as well. Id be prepared to replace all the hydraulic parts. And check fhr the booster to be full of brake fluid...