I have a 78 ford f250 and im having soft pedal and rear brake issues problems. Every thing is new i mean everything. brake lines, hoses, calipers, wheel cylinders, booster, master cylinder. I bleed the brakes at each bleeder till all air is removed. for the life of me i cant get the rear brakes to lock up even on dirt. I adjested the brakes till they have goog drag and still nothing. I was thinking it was my proportioning valve that went bad but when i bleed the rear brakes i get good flow back to the rear bleeders. I adjusted the booster push rod to within spec. The only thing i can think of is i might have to bench bleed the master cylinder again. this is a ground up restoration everything that could have been replaced was. any input?

 

Do they pump up hard or are they always soft?

 

They pump up hard when the engine is off but while driving they are soft.

 

You still have air in your lines. I can promise you. Check and make sure that all of the fittings tight and then you will just have to bleed them. I had the same problem on my 73 f-250. The master cylinder went out and when I replaced it there was so much air in the lines that I ended up taking it to a shop and have them do it.