I have a '78 F150 supercab 4x4 and last year, I went through the entire brake system and replaced the stock vacuum booster, master, prop valve (to an adjustable Wilwood version), all new nicop lines, stock front calipers, and braided flex lines front and rear. The stock booster/MC combo was crap to say the least, and I almost went for a ride going down a long hill on the test drive (the rotors got red hot and basically did nothing). Good thing for knowing to gear it down.

Anyways, it then sat over winter and I got a hydroboost/Wilwood MC/Saginaw PS pump combo and installed it. I got the PS system bled of air and it works great (at least as great as can be gathered while the front is on jack stands), but I'm having a hell of a time bleeding the brake system. I bench bled the MC--a few times now, I gravity bled the calipers/rear cylinders, I vacuum bled all four, and I had my son do the 3-pumps-then-hold routine. I'm pretty sure the fronts are alright, but I couldn't get more than a trickle out of the rears, even when my son was pumping them. And no matter what I've done, the pedal always just goes right to the floor. When I ran the engine, the booster assisted nicely in the pedal's trek to the floor, so that seems to work. I also went through all the fittings and gorilla'd them to just shy of rounding over with a flare wrench. My next step is to undo the lines and blow air through them, but I don't know why the master doesn't give any resistance. I'm so frustrated I'm about to take it to the scrap yard--it's already a summer and a half working on it without being able to enjoy it on the road. Anyone else ever have trouble bleeding these cursed things? Am I missing something? I also have a Motive pressure bleeder I haven't tried yet owing to the fact it's a total pain to setup, but I might try that if worse came to worse. And this isn't my first rodeo with brake systems and I generally have good luck with them... until this beast.

 

My two thoughts are... Did you check the adjustment of the rear shoes? How did you set the new proportioning valve up when you bled everything?

 

They are close... they drag a little bit, but not much. And I spun the valve all the way out, which should be "most brake".

 

I think all the way counter-clockwise is least pressure at the back and all the way clockwise is the most.

I say look around and make sure there are no leaks from anywhere and if that checks out bleed it all again. I recently changed everything out and I went through 2 liters of brake fluid getting all the air out. I also started with the bed up at an angle and finished with the front up at an angle. If that doesn't work call Wilwood and ask.

 

Thanks for the input Yeah, there's an arrow on the **** that points to least braking or something like that and I turned it to the stop on most braking. One other thing is I noticed the bleeders are junk... they leak more fluid around the threads than through the hole and I really have to torque them down to get them to seal (assuming they do). Gotta love quality control. I'll try the putting the front and back at angles... that sounds like a good idea.

 

Might try some new bleeder valves since your going to make a mess anyway.

 

check to make sure bleeders are not plugged with gunk, seen that happen before.

 

Sounds like a bad MC. I know its new but that's not a guarantee its not defective.
When you bench bled your MC was it super super tight and very hard to push?

I recently did my brake system and it took me almost an hour to properly bleed my MC in the vise. Fking Bubbles!!!
I couldn't even push it an 1/8" by hand, which hurt like a ****, when I stopped and installed it on the truck.
If you don't have air in the lines that's about the only thing, I think, it could be.

 

I'm not sure they're the right bleeders for the cylinders. It wouldn't surprise me if the PO cross threaded whatever size bleeder he had laying around into it... they're really loose when they're turned out even a little. I see Autozone has cylinders for about $14 each. They're the only things in the whole system I didn't change since I want to convert to rear disc sooner or later.

It wasn't super tight... it had the usual amount of resistance and the bubbles stopped after 5 or 6 pushes (I pushed about 30 times with breaks in between the last time I did it--no bubbles at all). Wow an hour? If it were me, the MC would have been taking flying lessons Last year when I went with the stock MC, it took 3 tries to get a reman that "worked". The first had some pretty bad scoring in the bore--well, what I consider bad anyways, the second had quite a bit of metal filings in it and the 3rd was the "charm". That's why I went with the Wilwood... I hoped they might have a little better QC than Cardone.

 

Did you check the brake booster rod length and the master cylinder bore depth ?

The rod should be 0.01'' shorter than the bore depth.