I've Got No Brakes!!

Hey all, we've been working on my little brother's 1956 Desoto Firedome 331 and we've ran into a snag. No brakes. We've replaced the master cylinder, replaced all the wheel cylinders, replaced the brake shoes, flushed the fluid and bled the hydraulic system, checked the hard lines for damage, replaced the soft lines, checked the combo block for leaks, and verified the master cylinder pushrod length.

So, after all this the pedal really only contacts at maybe the bottom inch of travel, and feels like there's no contact until that point. Only thing that hasn't been tinkered with is the power brake booster, but that typically causes a hard pedal. But the location troubles me, The booster and the master cylinder are bolted separately on the firewall.


What do you think could be causing this? Idk how the booster is connected, it seems like at the minimum the hydraulic brake system should be operating..

 

have you tried adjusting up your brake shoes?

 

Bench bleed the master?

 

Adjust all the wheels up to a slight drag. Make sure the push rod to the M/C has a very small amount of freeplay .020 thou is plenty ,just want to make sure the M/C piston is returning all the way. My Motor's manual shows that booster to be a Hydrovac style ,should have one line going into it from the M/C and one out. You need to bleed this first , bleeder closest to the big end first.

 

Another vote for bench bleeding the master. My roadster had this same issue.

 

Pushrod adjustments on booster & master first guess. Second would be brake shoe adjustment. Front wheels tighten in same direction as wheel rotation, rears, lead shoe same as rotation, trail shoe opposite direction

 

Another vote for bench bleed the master.

 

Make the horn really loud

 

If I was you I would give Jerry or Eddie a call.
chuck

 

Yeah, no avail.

I did prior to installing the new master cylinder. Still, no.

Now we're talking...

HAHA yeah except he's scratching his head with me.

I think i may have found it, since the master cylinder isn't on the snout of the booster, there's a lever that piggybacks the brake lever, and there's a small hole in which you have to unwedge the brake lever and the power brake lever to accurately check the freeplay and adjust accordingly. Sheesh. Chilton's guide ftw.

 

the booster? since its the only thing that hasnt been tinkered with?

 

yeah but a defective vacuum brake booster would cause a hard pedal, not a soft pedal. plus the base brake circuit should be operational, just the power not working.

i think it's the lever trick. instead of measuring freeplay off the pedal you need to unwedge the power brake and brake levers first.