Brake Pfroblem

I have a 1956 Oldsmobile Super 88. My friend and I replaced the wheel cylenders and shoes. We bleed the brakes and adjusted them properly. When I took it out to road test it, I had major brake fade. When I got it back to the house I had little to no brakes and the pedal went all the way to the floor. I checked the brake fluid and it was at proper level. We then bleed them again and this did not fix the problem. Anyone had this issue or does anyone one know what the problems is? The oldsmobile has a Power brake system.

 

Did you bleed with the engine running? Are the brakes properly adjusted. You appear to have air in the lines.

 

Did not bleed the brakes with the engine running. We adjusted the brakes properly and checked for air in the lines. I'm thinking my master cylender is bad.

 

when i have had a master go bad i could pump the pedal up and keep a strong pressure and the pedal will hold, but if i only keep a light pressure on the pedal it will slowly go down the the floor.

 

When We bleed the brakes the pressure would build up, but when I drove it the brakes would fade out causing the pedal to go to the floor. I never had this problem with any other brand of car except this Oldsmobile.

 

does the treadle vac unit leak at all? they are a pain- mines was rebuilt twice by a shop and still leaks and does the same thing. options are either go modern and change up the fire wall or rebuild it again. I would do a flush and insure air and any gunk is out of the equation, but mine has never been right.

good luck,

 

I have a similar prob......'60 Belvedere....booster grafted on.....bleeding with engine running.....what's the idea behind that?...I haven't done that but I'll try anything.
Thinking of going to discs but it ain't cheep.

 

I'm not sure if it's the same system as on my Cadillac but if it is there's also two bleeder valves on the power brake unit. Typically if you get brake pressure that fades there's a leak somewhere. If you have to pump it up but then holds there's air in the system.
I'm chasing a similiar problem. When I first push the pedal I hear what sounds like air been sucked into the system. As soon as the sound stops my brakes are at the top of the pedal.
It's always something...

 

These brakes are a real pain. I'm taking it to a shop Monday hopefully they can fix it.

 

I was going to say that the master cylinder primary cup is going bad, but that is a treadlevac you have and that one does NOT use the typical master cylinder approach. There are no primary cups on that model, only a secondary seal in the back of the master cylinder to keep fluid from being sucked back into the power brake unit.

Now comes my question: You say you changed the wheel cylinders? Did you put new copper washers on the front brake hose to cylinder on each side? If you use the old washers it will leak air into the system causing the issues you have. Take it from past experience.

 

I used the copper washers.

 

Old or new ones?

 

New ones that came with the new wheel cylenders. I got them from Canter Auto Parts.

 

Im the one that helped on this. Its not like the caddy hydro vac. Its wierd when the car is sitting the pedal doesnt go all the way to the floor but gets rock hard instead of haveing some cusion to it. I havent driven the car.

Ive delt with hydro vac where your supposed to bleed with the engine running and didnt have much luck. Lots of presure, too much noise and on this car you would die from the exausht. Im ussully pretty good with brakes but ive never worked with the tredelvac.

There appears to be no fluid leaking from it.