Hey guys! My 72 F100 has brakes that are for s#$%*! I have replaced shoes, hardware. I have bled the whole system. I have adjusted brakes according to book. I still have weak stopping. The pedal isn't hard. It feels normal to a little soft. I changed the master cylinder when I got the truck. As I recall there were two rods that came with the master cylinder...a shorter one and a longer one. I used the longer one as I have a booster. What the heck is going on? Am I missing something easy? My parking brake cables need to be reattached as they are not hooked to frame as the book shows. Is this messing up my hydraulic braking?
Thanks guy.

 

On my '72 F-250, the differential valve is activated whenever there has been a drop in the fluid pressure in either the primary or secondary brake system. It's the mechanism that makes it so that, in case of such a failure, the truck might still have brakes on either the RF & LR wheels or the LF & RR wheels, depending on which system lost pressure. I would think an F-100 would have the same basic system design.

The valve is located down on the left frame sidemember and you can find it by following the brake lines out of the master cylinder. If you've bled the brakes properly and have done all the other things you mentioned, I'd start looking at the pressure differential valve then move on down the lines.

Once tripped, it apparently stays tripped unless and until you re-center it. The symptoms include lousy braking and, when you're bleeding your brakes, a remarkable difference in the amount of fluid released between one side and the other. [That's the very problem I'm having right now...the valve on mine is tripped and I'm looking for an easy way to reset it and/or a source to find a replacement cheap.]

Good luck!!

 

Presupposing just for the sake of giggles that the source your braking problem is anything like what I was talking about, you might be interested in this thread I ran across in the '67 to '72 old truck forum:

https://www.ford-trucks.com/forums/s...threadid=102575

 

The cables are not messing up the brake system. I would suspect your shoes are not adjusted properly. Do a search in the 67-72 forum on my name and see how I did mine with all four wheels off the ground.