55 Cadillac Brakes going soft HELP!

[55 ledsled]

Hello,
I have a 55 Cad sedan that when I bleed the brakes, I get a fairly tight pedal, but when I start the car the pedal goes to the floor. I have done the following:

-Rebuilt the Master (Kit & lightly honed)
-All New wheel cylinders
-All new brake line
-New filler line (fittings leaked)
-Adjusted up all brake pads
-Cleaned out the small release hole that was blocked inside of the master, because at one point the pedal was building pressure but would not release unless I loosened up a bleeder (Once I cleaned out that hole, I have not been able to hold any pressure)
-No leaks anywhere
-Bleeding many times, done by both manual pedal pressure, and also with a small hand pump vacuum bleeder

The only thing I haven't done is I haven't touched the booster. I haven't rebuilt this. I have been told that if this does not work that I just won't get the extra boost? Is this correct? 

Before I spend money on either a new Master cylinder or pay to have the booster rebuilt, does anyone have any idea of what the heck might be going on? I do have a little brake but not much. My petal will also not return leaving my brake lights on until I pull up the pedal. I have attached photos of the equipment I have on the car.
Any help would be appreciated! Thanks

[LoStreet]

Hi, I should tell you at the start that I am no mechanic.  I hope others more experienced than me (which is nearly everyone on this site) will eventually reply.  But over the past year-and-a-half, I have had four mechanics work on my brakes, with only the last one (and maybe the first one) getting my brakes to work at all.  I will relay two issues that may affect your '55:

1.  The plunger inside the master cylinder is VERY tricky.  It has to be aligned exactly with the pedal.  If it doesn't depress properly, in my case, the cylinder would, for lack of a more technical term, gum up and freeze the brakes.  It is tricky to diagnose because when the car sits, it lets up and the brakes work fine for a short while.  I experienced a couple of times when the pedal was spongy because of this, but not that often like yours.  May or may not be your problem.  I was told by several that often the rebuilds from the standard classic parts houses (won't mention names) are defective, but since you say you rebuilt your own, you would know better how the plunger operated.

2.  All of the first 3 mechanics said brakes would work without the booster working.  I don't know.  All I know is that they never worked right until I replaced the booster with a rebuilt one (to the tune of about $350).  Definitely worth it to me.

Good luck.

[Jeff Rosansky CLC #28373]

The booster amplifies your pressure. A couple things come to mind. First, what about your rubber brake lines. Have you replaced those?
How long will it hold pressure with the engine not running?
We're you able to fully bleed the booster?
Pull off the vacuum line going to the booster. Is there any hint that brake fluid is getting sucked thru? That would indicate a bad seal.
Jeff

[Mike Josephic CLC #3877]

One thing should be mentioned here -- if the
Hydrovac fails, you will not only lose braking power,
you will have total brake failure -- NO BRAKES.

The master cylinder gets it's brake pressure from
the Hydrovac -- it's the weak link in the system.
It doesn't work like a modern "booster".

Since you have rebuilt everything else, I highly
recommend that you have the Hydrovac rebuilt
by somebody who knows how to do it correctly.

Here is one source:
http://www.pwrbrake.com/inventory/search/

Ed Strain used to be the "go to" guy, but his business
was bought out by White Post Restorations.

Mike

[Dave Shepherd]

No mention of bleeding the Hydrovac?

[fishnjim]

You're in the early period of booster brakes, and they had design problems throughout this period until they went to dual systems around '64. 
I'm already old, so I don't need something to make me, so I don't mess around, I yank them and put in modern dual, but if you insist on retaining original brakes, then I'd find a old timey mechanic, not many left, and learn everything I could about my system.  Some of the new parts are problems because the old ones don't exist, and some of the original stuff gets worn/out of tolerance and may never be right again.   About all they can do is put in available replaceable parts.   There's camps that say it's the fluid and camps it's not, and some claim their's works flawless and some never, so it's part of the territory here.  Seems like once they go bad, you go into the twilight zone.   I don't like loosing brakes in a ~5000 lb car with no crash protection.
As I understand it, which maybe incorrect for your year, the booster has to be bled to get pedal and when it loses pedal that fluid is going somewhere it's not supposed to.   I never did find out where, no leaks, I always suspected it was going out the vacuum, because I was adding fluid, but none in the hose or vac reservoir, so they're kinda mystery.   I gave up and yanked it all.  And your's is older vintage than mine, and they were "fixing" problems yearly as they went.

[Mike Josephic CLC #3877]

On the Hydrovac, the brake fluid typically is sucked
into the intake manifold when there is internal
failure.  You can verify this by removing the vacuum
connection and check it to see if it's "wet".

If it is, it has an internal issue.

Mike

[fishnjim]

Well, Mike, '58 did not connect directly to the manifold.   The vacuum line goes to the reservoir on the early cars to provide enough vacuum to actuate the brakes when there's not enough vacuum.   Plus there's a bunch of branches for the vacuum pump, wipers, etc.   Not a direct manifold path like in the later cars.   There's a check valve in line to prevent back flow.   That was part of the mystery.   
The people that changed the system said there was problems at the wheels, but it would drive and stop OK, just all of a sudden lose pedal.   And you had to bleed booster to get it back.  The brakes were supposedly, "rebuilt" and I had pulled and checked all the wheels prior to putting on the road.   It just wasn't safe to drive.
After I started to investigate these boosters, I found a whole litany of issues mostly, last ten years due to internet access, so I don't know if that's due to the age of these units or the parts and materials, know how, being used to repair them now.   There's no failure statistics in the day because they didn't keep them back then.   Probably some at the manufacturers, maybe insurance, but they wouldn't keep or divulge bad info and some defunct.   But the first highway safety act came in '64 from people dying on the highway, so there were some nasty problems during the post war.   I recall the highway patrol safety films of the carnage and family members going through windshields during wrecks.
Frankly, it's moot for me, it's on the shelf, but there's some issues with these early systems that just doesn't seem to go away.   That's why I recommend anyone having problems to be very careful and consider upgrade.   
I'm older than these cars, and I don't recall that much problems with brakes when they were new.   But that has to be in period perspective, there weren't today's knowledge,   
safety, etc. and driving was done a bit different.   I do recall the pre self adjuster brakes requiring frequent adjustment and it was a nice to get that change.

[Mike Josephic CLC #3877]

Hi Jim:

I agree with what you say -- but I was, of course,
referring to the OP's 1955.  On that car, the Hydrovac
vacuum line does go directly to the manifold.  I have
one on my '55 Eldorado.

I've been around a few years myself and yes, like
yourself, I'm older than those cars.

I enjoy your posts, by the way.

Mike

[55 ledsled]

Thanks Everyone!
I did bleed everything correctly starting with the booster, then the main line going to the 4 way splitting block and then from rear to front...about 10 times lol. Brand new rubber front lines as everything is new except the booster and I rebuilt the master. The booster does connect directly to the manifold, and I will double check for brake fluid in it but I dont think there is any because brake fluid that burns makes a lot of smoke. I think I am going to just bypass the hydro booster and see if that is indeed the issue being they want stupid money for a rebuilt unit.

Again, I had the situation where the 2nd tiny hole inside of the master cyl. was plugged that is supposed to release pressure as when I did have brakes, the pressure built up so much that the pedal went solid and would not move unless I cracked a bleeder. That resolved the buildup issue. Now it just goes to the floor.

I will keep ya all posted on what my findings are. Thanks again for your input   

[Bob Kielar]

My 55 Fleetwood brake booster vacuum connects directly to the intake. Where does yours connect?

Keep Cruzin,

Bob Kielar

[55 ledsled]

It connects directly to the manifold.

[Jeff Rosansky CLC #28373]

I think I am going to just bypass the hydro booster and see if that is indeed the issue

Keep it simple before you re plumb the system. Just get a plug and plug the output of the master. If you have pedal then your problem is past that.
Don't forget that if you go to manual brakes you need to install the check valve in the master so it will need to come out again anyway. I think it was about $250 to have my booster rebuilt.
Jeff

[55 ledsled]

Gotcha, plug the main out of the master to make sure the master has pressure before I go on. Thanks for the info on the cost of a rebuild. I was thinking of attempting to do it myself but was not sure if special tools were needed. Thanks again!

[fishnjim]

I did some checking, and here's the exploded view of the booster, but it's only typical as there was apparently some minor changes in '55, orientation, etc. which is not unusual.  Separate part number.   When there's this many parts, anyone can cause problems.   

I'd recommend you get this cleared up completely, before you trust your brakes - a safety system.   The few dollars is not worth the risk.  If this was the first time I've heard this happen, I might think differwntly, but it's too common.

[55 ledsled]

Update!
Plugged the main line out of the master cylinder, and the master that I rebuilt is working just fine. Stiff petal so the master is holding pressure. I guess I will yank out the brake booster and have it rebuilt. I guess now we know that if the booster is bad, that there is a chance that the brakes will not work as expected or just bypass.

Now, does anyone have any experience in bypassing the booster, meaning connecting the main line from the master out to the smaller main line that goes directly into the 4 way splitter. Someone mentioned that a check valve would be needed? Could that person please explain?

Thanks again everyone! This forum has been very helpful to me along the resurrection of my 55.

[Jeff Rosansky CLC #28373]

This thread will explain it better than I can.
Look at the Feb 25th post. 54 had a check valve in the master. 55 moved it to the booster. Based on this if you remove the booster you will not have a checkvalve.
Jeff
http://forums.cadillaclasalleclub.org/index.php?topic=139787.msg327499#msg327499

[55 ledsled]

Thanks. I couldn't find any 54 check valves anywhere on the net for manual brakes, only for brake systems with boosters which I can see needing with the extra boost. Check valves are in place to keep fluid going in 1 direction and not back. Wouldn't you want the fluid to go back to release the pressure from the wheel cylinders?

[35-709]

Residual check valves, the why and wherefore ---
https://www.freeasestudyguides.com/residual-check-valve.html 

https://www.youtube.com/watch?v=6B8a6enp1bg

[35-709]

Also, without a small amount of pressure the strong return springs on the brake shoes would pull them further back to the point that the next time you applied the brakes the pedal would go way down before braking action would occur.  If you applied the brakes again in quick succession you would find the pedal firmer and higher so you would end up pumping the brakes all the time to get a good pedal.  The residual check valve helps eliminate all that.