1955 Buick Super Brake Issues

[Cronjie]

I bought a 55 Super last fall and among the issues it had was a spongy brake pedal. We inspected the brake shoes, cylinders (none leaking) and did the various adjustments. All looked good. Figured we might have air in the lines so we began to bleed the brakes. On the first opening of the rear passenger bleeder the pedal immediately went to the floor. We were never able to pump it up and get any pressure. We have plenty of fluid in the reservoir but were never able to get any pressure back no matter what we did. Wondering if it might be the booster. Any ideas? Thanks, Paul

[avgwarhawk]

Rebuild the master cylinder. 

[Cronjie]

The booster is the master cylinder. I would like to do that if I know that is the problem and if I can get parts to rebuild it. 

[Cronjie]

I notice Fusick carries rebuild kits. Has anyone used any of these with success? Any tips?

[EmTee]

Check out this thread: https://forums.aaca.org/topic/373397-me-and-my-1956-buick-roadmaster-4-door-sedan-model-72/page/2/#comment-2377155

[old-tank]

6 hours ago, Cronjie said:

The booster is the master cylinder. I would like to do that if I know that is the problem and if I can get parts to rebuild it. 

The master cylinder is separate from the booster.  HERE you can get parts  to fix either or both.  Fuscik gets their parts here.

[JohnD1956]

17 hours ago, Cronjie said:

On the first opening of the rear passenger bleeder the pedal immediately went to the floor. We were never able to pump it up and get any pressure. We have plenty of fluid in the reservoir but were never able to get any pressure back no matter what we did.

The question in this thread begs the answer that no, there is nothing wrong with the booster.  Maybe the master cylinder, but perhaps not depending on several factors as follows:

As you know, the master cylinder in a '55 is under the drivers side floor. This has the potential to place the MC lower than the wheel cylinders which might make gravity bleeding of the system more of a challenge.  

The bleeding sequence has been the subject of discussion before.  Whether to start at the furthest or the closest is the subject of much debate.  It appears both can work but for this particular car it may help to bleed the fronts first. 

Note that this system is closer to cars older than 55 vs newer than 55.  The 56 for example has the MC located low on the firewall, above all the wheel cylinders and will successfully gravity bleed in most circumstances.  So be careful when considering advice relative to newer than 55 Buicks. 

While it would seem that if you had pedal pressure, even if spongy, before opening the bleeder, then you should have it after, but there is the possibility that a cup in the MC got torn in the bleeding process. 

My suggestion would be to raise the opposite end of the car above the bleeder you want to open, then see if the system will gravity bleed before using pedal pressure to finish the job.  I would still go to the back passengers side first as the longest run and the most air to be expelled.  And I would go through every bleeder before expecting any pedal pressure, which I am assuming you did.  You may even want to pull the bleeder valve out of each bleeder to make sure the seat is not pitted or broken and therefore not sealing when closed.

 

 

[60FlatTop]

I have been providing moral support to a friend chasing a brake bleeding problem. My last suggestion to him was picking up a couple of brake line flare plus so he can isolate parts of the braking system working out from the master cylinder. I had used the technique in the past.

 

Isolating the master cylinder and bleeding it to a hard pedal gives you a + on that part. If it doesn't come up to a hard pedal something in that section is amiss.. At the distribution block the front and rear brakes can be isolated. Then through the hoses and out to the wheels, achieving a hard pedal on each step as you progress.

 

Hoses can de-laminate internally and possibly trap air. When in doubt I like to remove the brake hose and slide a piece of #10 wire through it.

 

If you are uncertain of the brake fluid type you can put some water in a saucer and drop a sample of the fluid into the water. Mineral oil based fluid will be absorbed an turn milky. Silicone will bead up and bounce off the surface of the water. You don't want to mix them in the system and there is usually no documentation over years of service. You can test any car by taking a sample from the reservoir or off a bleeder, both would be best.

 

 

[Cronjie]

Well I found the reason for my brake issues. I started disconnecting the lines from the booster to remove it and found that there was very little fluid coming from the line that is connected to the reservoir/ fill tube. I figured it might be plugged with crud or something, so I removed it and dumped it out. Out came a paper disc like the kind that fits up under the cap of a brake fluid bottle. It must have fallen into the tube when someone was filling it up. Once that was out, I cleaned the filler tube and re attached it to the line. Hooked the booster back up and bled the brakes. Plenty of pedal and brakes now.