FLYER15015 Posted May 30, 2014 Share Posted May 30, 2014 (edited) Moved this here from another thread that had arbitrarily and without intent gotten hijackedLamar, your friendly modBhigdog,What's the deal with your brakes ????Got us all curious now............... Us BIG car guys gotta stick together................Mike in Colorado Edited May 30, 2014 by MrEarl (see edit history) Link to comment Share on other sites More sharing options...
Bhigdog Posted May 30, 2014 Share Posted May 30, 2014 Loooong story/rant. When I restored the car I sent the booster to a rebuilder in FL. Came back looking good but would not stop the car. Finally figured out it was bad brake shoes and put different ones on. Now the car would stop but the pedal was slightly soft and would stick down if applied heavily. Added an additional return spring to no effect. Called the rebuilder and he said send it back and he would check it out. To those who have never removed/replaced a 57 booster count yourself lucky. Anyway, pulled it out, sent it down and it came back as checking fine. Put it back on and still the same softish and sticking pedal. That's a few years ago. Been nagging me ever since. Finally decided to address the nagging problem again. Bought new linings again, checked everything over, bled the brakes until my wife's leg was sore all to no effect.OK. I decided the MFing booster was bad and started making calls to rebuilders. Talked to one that talked a great story. Really bad mouthed the FL rebuilder and told me for $390 they would rebuild my rebuilt booster and include lining the MC bore with a stainless liner. Well that's a great deal until you realize that it's a displacement type system and the MC bore is a rough casting that NOTHING touches. In other words the guy was BSing me or was clueless. I really feel sorry for the babes in the wood type car owners who are regularly fleeced.Anyway, and now determined to figure this all out I pulled the F***ing booster again. This time I spent hours reading and rereading the manual until I understand how and why it works. Pulled the booster apart and checked and rechecked. The only thing I didn't like was the Florida rebuilder used a LOT of heavy graphite grease on the power piston and for some reason plugged up a weep hole with silicone sealer. Other than that everything looked good. Cleaned it up lubed the piston cup with ATF as per the book and put it all back together.I then filled and bench bled the MC getting all of the air out. Then I vacuum tested the unit by running a hose from the car to the unit on a bench next to the car. First with a tube from the outlet to a jar to catch the brake fluid. Seemed to work good. Then I plugged the outlet to simulate a closed system. EUREKA. the unit worked great with a hard "pedal" and the best part was when I pulled the rod aft the piston retracted with no sticking.So, happy as a clam, I spent most of the afternoon skinning my hands reinstalling the booster. Now I have a nice hard pedal but it still sticks down and won't come back up with out some help or waiting a few seconds. So now the thought is that it MUST be the pedal linkage that's binding but the problem with that theory is that if I turn the engine off and repeatedly depress the pedal it will stick down until the vacuum can is depleted. As soon as there is no vacuum the pedal does not stick. Therefore it MUST be vacuum induced but why just on the car and not the bench. Therefore it must be the linkage. OY VEY.Laying in bed last night I was thinking the only difference in the bench and car test was that in the car I have a rubber dust boot on the push rod/booster. But that should make NO difference because the vacuum can is open to ambient pressure aft of the power piston. OY VEY.So it's back to laying upside down under the dash, skinning my hands with a hot trouble light rolling onto the side of my face, while I try to figure some logical set of conditions that would cause the problem. Link to comment Share on other sites More sharing options...
old-tank Posted May 30, 2014 Share Posted May 30, 2014 Bob, as a test remove or vent the dust boot. Last year I changed the boot on my 55 and the pedal stuck down when applied (that was the only thing that I changed)...removed boot and it worked fine. I could see no reason for this either.Willie Link to comment Share on other sites More sharing options...
Bhigdog Posted May 30, 2014 Share Posted May 30, 2014 Just slid it down the rod away from the booster. No change. Next step is to disconnect push rod from pedal linkage and see if I can duplicate sticking by manually pushing in rod. Not sure if I can get enough clearance to work it. I've walked away from it for the rest of the day. Getting the Olds ready for Ault Park concours. Thanks for the thought though...........Bob Link to comment Share on other sites More sharing options...
buick5563 Posted May 30, 2014 Share Posted May 30, 2014 I had to send back a 58 booster to that guy in Fla also. Does the same thing (still) after another rebuild. Keep us posted if ya figure it out.Sorry for the continuation of the highjack. Link to comment Share on other sites More sharing options...
MrEarl Posted May 30, 2014 Share Posted May 30, 2014 (edited) When I got my power brake master cylinder back from Power Brake Exchange in CA, the boot of mine had been split obviously with a blade. I called them and they explained to me that they do that to all 54 Buick boots in order for the unit to "breathe". Why Buick didn't realize a brake booster needs to breathe is still beyond me.... Edited May 30, 2014 by MrEarl (see edit history) Link to comment Share on other sites More sharing options...
buick man Posted May 31, 2014 Share Posted May 31, 2014 …… "Well that's a great deal until you realize that it's a displacement type system and the MC bore is a rough casting that NOTHING touches."Bob can you elaborate on that thought of a displacement system a little more for us mentally challenged? Link to comment Share on other sites More sharing options...
60FlatTop Posted May 31, 2014 Share Posted May 31, 2014 My '60 has a filtered plastic breathing box on the inside of the passenger compartment. It penetrates the firewall.Remember about 30" of vacuum equals 14.7 PSI, 20" puts you in the 10 PSI range.Bernie Link to comment Share on other sites More sharing options...
john hanson Posted May 31, 2014 Share Posted May 31, 2014 Heres what happened to me. Brake pedal keep sticking down. did like you did changed all kinds of things. then one day I pulled the master cylinder again. I had a nos kit on hand and check the parts out. the one in my master cylinder was a little shorter then the new one. I put the new one in and and problem was solved.This is the spring that is about 4" long inside the master cylinder.and it is not very strong. somebody may have put a Special kit in my 1938 Roadmaseter. You never know.John Hanson Link to comment Share on other sites More sharing options...
Bhigdog Posted May 31, 2014 Share Posted May 31, 2014 …… "Well that's a great deal until you realize that it's a displacement type system and the MC bore is a rough casting that NOTHING touches."Bob can you elaborate on that thought of a displacement system a little more for us mentally challenged? In a displacement brake system instead of a tightly fitting piston forcing fluid out of a cylinder, a smooth rod (piston) is forced into a larger diameter cylinder. Rather than "pushing" the fluid out the rod just displaces a volume of fluid equal to it's size. The rod has a bearing and seals at it's back end and never touches the walls of the MC which need not be smooth or even machined. The cylinder can be tapered so the volume of fluid displaced is disproportionate from initial pedal application............Bob Link to comment Share on other sites More sharing options...
buick man Posted June 1, 2014 Share Posted June 1, 2014 (edited) So Bob, from what you report, there is no way a 1957 Buick MC can be sleeved, and furthermore we assume no way this displacement type piston can go bad from sitting as would happen regularly with a positive sealed type tight piston with rubber ring system?O.K. I get it. But let's suppose for the heck of it, you let your displacement system 57 Buick sit for an extended period of time and discover no solid brake pedal. You immediately assume a faulty MC due to leak by or bad wheel cylinder(s) but can see no leakage from the cylinders. So you naturally then check the fluid level in the MC by popping the top 7/8 nut cap and discover it is down considerably but not empty. Hmm, So you fill it up and seal the nut on top. You then go and pump the pedal but to no avail and again no solid or pump up of the pedal. Hmm, So you disconnect the out going feed line of the MC and again pump the pedal. Assuming a displacement rod would be pushing fluid under any condition, you discover no fluid is coming out of this main line MC ?? So what is the problem here and how can these MC go bad? If the displacement cylinder is not a sealed psi system then it should be displacing fluid out under all conditions of the MC. Correct? BTW: This is happing to me right now and trying to figure why no pedal and no pumping of fluid. You also mentioned this system's rod has a bearing and seals at it's back end to assure what that no fluid is leaked out of the rod travel area/cylinder ? Please clarify and advise. Edited June 1, 2014 by buick man (see edit history) Link to comment Share on other sites More sharing options...
Bhigdog Posted June 1, 2014 Share Posted June 1, 2014 In 57 Buick used either a Moraine or Bendix booster. My comments refer to a Moraine unit. Addressing your comments. The MC could be sleeved with some creative machining but there is no point in doing so since there is nothing that actually rubs or touches the cylinder bore because the displacement plunger is much smaller in diameter than the bore. Indeed the MC bore, as produced by Moraine, has just a rough as cast surface. We can't assume the plunger can't "go bad" from sitting because it is steel with a smooth ground surface finish. In the un-applied brake position the plunger is almost fully retracted from the MC and is exposed to ambient air inside the vacuum can. It can therefore rust and the resultant rough surface degrade the lip seals. To answer your last question. When I said the plunger is supported at it's back end that could be misleading depending on plunger position. The plunger is fastened to the power (vacuum) piston. As the piston moves forward it pushes the plunger into the MC through a lip seal, a bronze bearing, and two addition lip seals. The bearing and lip seals support the plunger and nothing other than the plunger inters the MC bore displacing the fluid into the wheel cylinders which apply the brakes.The Bendix unit is built a bit differently but is very similar in design and operation. They are both totally sealed units ( or should be to work properly )It would be difficult to diagnose your problem from here other than to opine the various MC seals have been degraded, fluid has leaked and been replaced by air, and you have air in the MC and likely the line (s)..........Bob Link to comment Share on other sites More sharing options...
buick man Posted June 2, 2014 Share Posted June 2, 2014 Thank you Bob for the explanations. I have yet to tear into my unit and asked these questions instead of looking into my shop manual but was curious to your replies just the same. It appears now that the end seals can go bad since on mine if you disconnect the only single fluid delivery line out of the front of the MC rendering no resistance and no fluid comes out when the brake pedal is pressed then indeed these seals you speak of must be the culprit. Interesting how a couple of well advertised and renowned MC rebuilders I contacted were eager to rebuild my MC and offered the customary brass or stainless sleeve job for this MC. I will remove and tear mine down and get a fuller understanding and report back. Link to comment Share on other sites More sharing options...
Bhigdog Posted June 2, 2014 Share Posted June 2, 2014 Dave & Mike. I've made some progress but no fix yet. I removed the unit yet again. One bright spot is that I'm getting good at it and can have it out in 30 mins or less. Another bright spot is that I've established that the problem is in the booster and not linkage etc. I guess two trips to the Florida guy wasn't enough. I've also established the fault is in the power piston assembly. I'm guessing some seal/valve is not quickly dumping vacuum when it's asked to. Next step is to disassemble the power piston, by the book, and look for the obvious. I'm also going to make a different style big nut that goes on the unit inside the car under the dash. Mine will have drive dogs rather than flats so it can be tapped tight or loose with a drift and hammer. .....................Bob Link to comment Share on other sites More sharing options...
buick man Posted June 3, 2014 Share Posted June 3, 2014 Well Bob, that's a great idea. Perhaps dogs will be accomplished by cutting U shaped notches on the Hex surfaces with a dremel or whatnot or one could drill holes in a circumference pattern along the face of the nut itself that your drift would match. The OEM nut on the unit is narrow faced and a wider face nut would be required if going that route I suppose. Link to comment Share on other sites More sharing options...
Bhigdog Posted June 3, 2014 Share Posted June 3, 2014 Nut won't have flats at all. Look more like a gear with maybe 8 teeth or cogs. It's relatively easy to reach the nut with a drift to tap it tight/loose. With a wrench not so much............Bob Link to comment Share on other sites More sharing options...
Caballero2 Posted June 3, 2014 Share Posted June 3, 2014 If you have not already done so, try the major brake adjustment detailed on page 9-16 of the Chassis Service Manual.Dan Link to comment Share on other sites More sharing options...
Bhigdog Posted June 3, 2014 Share Posted June 3, 2014 Thanx, but been there done that several times. Problem is definately in the booster. ..............Bob Link to comment Share on other sites More sharing options...
john hanson Posted June 4, 2014 Share Posted June 4, 2014 Would you like to try a new booster and master setupJohn Hanson Link to comment Share on other sites More sharing options...
Bhigdog Posted June 4, 2014 Share Posted June 4, 2014 Perhaps. What do you have in mind. If it's business PM me................Bob Link to comment Share on other sites More sharing options...
buick man Posted June 4, 2014 Share Posted June 4, 2014 (edited) I currently own two Roadmaster 57 Buicks and have had 3 57 Buicks before that, a Special, a Century Convertible and a Caballero over a 45 year span and have never had trouble with the brakes or pedal on any of them. The brakes would put you into the windshield if you want on any given day ! Stay stock you can cure the problem. Edited June 4, 2014 by buick man (see edit history) Link to comment Share on other sites More sharing options...
TG57Roadmaster Posted June 4, 2014 Share Posted June 4, 2014 Have you taken off the air filter cap and applied a small amount of oil to the leather "cup" that's in there? The procedure is covered somewhere in one of the manuals. LargerLargerIt could be something that simple. That solved my similar problem some years ago, and it hasn't been a problem since.Hope it works!TG Link to comment Share on other sites More sharing options...
Bhigdog Posted June 5, 2014 Share Posted June 5, 2014 Thanks for the thought but no that's not the problem. I have increased the rate of the spring that returns the air valve (shown at bottom center ) and that cured the sticking pedal problem, at least on a bench check. Leaving for Ault Park concours tomorrow and won't get chance to install and try the unit in the car. Not sure how the increased rate will affect overall operation of the unit but will find out next week........Bob Link to comment Share on other sites More sharing options...
therios Posted June 5, 2014 Share Posted June 5, 2014 Oh, boy. I hope I have better luck.I just shipped my 57's MC/booster unit to a well-known brake booster rebuilder in Florida. I'll let you know how it turns out.Ike Link to comment Share on other sites More sharing options...
buick man Posted June 5, 2014 Share Posted June 5, 2014 Find a bench and a good overhead light system and tear into it. Then order the parts you need. How hard can this be? That's what I'm doing so we'll see ... Link to comment Share on other sites More sharing options...
Bhigdog Posted June 5, 2014 Share Posted June 5, 2014 57 Booster sticking pedal update. The small spring shown in post #22 at bottom center pushes the air valve open upon pedal release and dumps vacuum from the can allowing the big piston spring to push the piston to the brake un-applied position. Thinking that small spring has weakened over the years I stretched it from .750" to about 1". The unit bench tested good after the "fix". I rough re-installed the booster in the car this AM and it seems good. No pedal sticking and the car stops. The pedal still needs to be adjusted for height and the system bled but so far it looks good. I won't be able to get back to it until next week.If this is the fix for a sticking pedal it's relatively easy to do after the unit is removed. The lock ring is removed and the push rod pulled out along with the spring. Be careful not to lose any small spacers on the air valve. Stretch or replace the spring and reassemble. The hardest part of the job is dealing with the heavy snap ring. If the unit starts sticking again I will replace the spring with a new one rather than stretch the old one. That was a temporary fix but now that the unit is back in the car I'm going to call it done.A couple of questions occur to me regarding a re-builder in Florida. After I got the unit back with a sticking pedal and sent it back why did he say it checked good when even I could duplicate the problem when I bench tested it? Why did he say to just add another pedal return spring when that could never, and didn't, fix the problem? Was he just blowing me off? Why did he plug a weep hole with silicone that is designed to be there and the manual even mentions? Why is a part shown (snubber) missing from my unit? Is the missing snubber part of my problem? .........Bob Link to comment Share on other sites More sharing options...
buick5563 Posted June 5, 2014 Share Posted June 5, 2014 One other thing. When I got the one back that my customer had rebuilt, the brake light switch was broken and there was a dent in the canister. I guess one could blame UPS, but it wasn't really well packaged.I will check that spring the next time it comes in to me. Y'all know how easy it is to just pull it out Link to comment Share on other sites More sharing options...
Bhigdog Posted June 5, 2014 Share Posted June 5, 2014 Taking the turn signal and neutral safety switches off the column helps a lot..................Bob Link to comment Share on other sites More sharing options...
Bhigdog Posted June 18, 2014 Share Posted June 18, 2014 (edited) Finally got time to finish installing the 57's booster and test drive it. Lengthening the spring that I mentioned above fixed the pedal sticking problem. No matter how hard I push on the pedal it returns back with no delay or hesitation. Brakes work fine.It's pretty strange that dumb ole me could figure out the problem and the fix, yet a booster rebuilder in Florida either didn't know what the problem was or just couldn't be bothered to install a proper spring. Stranger still when you figure that with the unit on the bench it would have taken no more that 2 minutes to do so. Oh well. I hope this thread helps someone down the line............................Bob Edited June 18, 2014 by Bhigdog (see edit history) Link to comment Share on other sites More sharing options...
60FlatTop Posted June 18, 2014 Share Posted June 18, 2014 Wait until you get to be my age and start dealing with "professionals" in the medical community. The guy in Florida is going to look like a genius.Bernie Link to comment Share on other sites More sharing options...
Bhigdog Posted June 18, 2014 Share Posted June 18, 2014 Wait until you get to be my age and start dealing with "professionals" in the medical community. The guy in Florida is going to look like a genius.BernieI hear you, Bernie, I hear you. As far as old cars go I truly feel sorry for the guys that have to farm out most of the work to "professionals"...............................Bob Link to comment Share on other sites More sharing options...
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