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DrP

1963 Brake Booster failing to boost

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Installed a rebuilt booster from Booster Dewey. Replaced master cylinder, all new lines, all new brake hardware; everything. Filled with Dot 5, then bled system. Good brake pedal but booster does not provide boost. Vacuum to booster is good. Any ideas what I should do before taking it off and sending it back? Desperate.

 

Thanks,

Dale 

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I agree. That little square-edged O-ring makes all the difference. Ask me how I know. Booster Dewey will send you one. I can't say enough good things about their service to ROA and other vintage car clubs. 

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Would this apply to 64 as well? One of our chapter members has experienced this for some time before and after work by a reputable professional mechanic.

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When I installed a dual master cylinder on my '64, I contacted Booster Dewey and he advised me to reuse the rubber boot gasket that came from my original master cylinder.  I asked him about the "square" o-ring and he told me that it wouldn't be necessary.  I don't know if the original can be used in lieu of the "square" o-ring or if the '64 setup is different than the '63 setup.

 

Ed

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Thanks to all for advice. Believe this will be the solution as it did not go together using the O-ring as it should have. In the process of removing and re-installing. I'll let you know.

Dale

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Just installed the O-ring from Booster Dewey after the third time we've had the booster off. Didn't seem to help. Bled the system - again. Still getting a "hard" brake pedal and no boost. Vacuum to booster good. It seems the push rod to master cylinder may not be plunging all the way. Is there an adjustment needed on the rod? Are there specs for the adjustment? Could it be a faulty booster?? How do I measure that? Booster Dewey says not likely and we should measure brake fluid pressure at 800 psi specification. (Don't have a gauge that goes high) Anyone else have this dilemma when installing rebuilt booster and m/c?

Getting frustrated so any help is appreciated.

Dale

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                      What you have is a defective rebuilt brake booster. If pedal height is normal and firm and you have to stand on the pedal with

two feet to stop......you have a bad booster. Send it back to Booster Hughie, Dewey and Louie. We see defective reman boosters all the time in my shop. About one out of five we install has to come back off because it does nothing at all.

Edited by Seafoam65 (see edit history)

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Sounds like a frustrating problem. I'd remove the master and verify the piston moves freely through full stroke. Booster Dewey has a very good reputation but I am a surprised at the suggestion to check fluid pressure to 800psi. Unless we are missing part of the conversation, that is a rather odd recommendation considering the symptom of no boost. It sounds like the valve inside the booster that opens vacuum to the front side of booster is not working.

Out of curiosity, try connecting a vacuum gauge into the booster tank circuit. Start engine to build vacuum then shut off. It should hold vacuum. Then apply brakes and see if vacuum drops off with each push of the pedal. If not, the internal valve is not working. Once you confirm 100% the master is not at fault, the booster needs returned which is a real pain because of the time lost then fight over who pays the shipping charges but if booster is defective they need to cover costs both ways.

 

One more question. Do you have braking action to the wheels but just a hard pedal? You should still have braking action only it will take a lot more force on the pedal. If no action verify master cylinder as above then try pushing brake pedal without the master bolted to the booster to insure pedal moves freely.

Edited by JZRIV (see edit history)
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Be sure you have an adequate vacuum supply to the booster! Is it possible the current vacuum hose is collapsing and blocking the proper volume of vacuum? Might you have a vacuum leak on the supply side which you are not hearing because the engine is running?

I know it sounds amateurish but before I went thru the labor and hassle of removing/returning the unit I would use a new length of vacuum hose (I already have it in the shop) and another running car as a vacuum source to completely eliminate the possibility you have a problem on the supply side. After all, this is the issue you had before replacing the booster, right? I would double check my diagnosis before I condemned (along with the hassle/cost) of another mechanic`s work.

I have been burned a couple of times with carb base gaskets collapsing into the vacuum chamber under the carb and dropping vacuum levels below the threshold level of the booster. Good luck,

  Tom Mooney

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I had the same problem. and found that the vacuum hose to the booster was leaking at the booster, so a small clamp

was used. No more problem!!!

Rocket 88

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Thanks JZRIV, Tom and Old Crow and others. Did all these suggested checks and troubleshooting but still hard pedal and no boost. Talked with Booster Dewey and agreed it is likely the booster. So....booster is coming off and return for inspection and re re-build. Will advise. 

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Well, got the booster off to Booster Dewey and he said they totally disassembled it and found an internal "hose defective". Got it back on the car and everything is working fine. Just a pain having to remove and replace several times. Now it's drivable and on to other small repairs.

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On 3/15/2016 at 5:17 PM, Seafoam65 said:

                      What you have is a defective rebuilt brake booster. If pedal height is normal and firm and you have to stand on the pedal with

two feet to stop......you have a bad booster. Send it back to Booster Hughie, Dewey and Louie. We see defective reman boosters all the time in my shop. About one out of five we install has to come back off because it does nothing at all.

Mr. Seafoam, I had a new dual master cylinder replaced on my rebuilt Dewey brake vacuum booster.. The brakes with the single master cylinder were working fine until the dual master cylinder was put in. I have brakes with the new dual master cylinder

, but not power brakes. It is a hard pedal, but I do have brakes. Would you care to speculate the problem?  Many thanksRed Riviera Bob

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Taking the O ring off the single master cylinder and reinstalling on the new dual master cylinder. I’ll keep the forum aprised of progress.

Red Riviera Bob

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On 4/11/2016 at 1:35 PM, DrP said:

Well, got the booster off to Booster Dewey and he said they totally disassembled it and found an internal "hose defective".

 

Dewey rebuilt and cad plated my "60 booster quite a few years ago. I was happy with the service.

 

"Defective hose" is interesting. Vacuum and fuel hose diameters have changed over the past few years and most come on an external MM size, yet marked fractional per the ID. I had a hell of a time with the Corbin clamps on my fuel lines last time I worked on the '60. The OD of the 5/16" lines is just a bit smaller and the clamps won't clamp. I bought about 20' of fresh and ended up digging out a length that is probably 15-20 years old to get things the way  way I wanted with the original clamps. It is possible something like that happened.

 

As I read the first few comments I wondered why vacuum had not been applied as part of the original diagnosis. I have a couple of MyTeeVac hand vacuum pumps with a bunch of hoses and fittings that I use fairly often. They are real handy for verifying hoses, connectors, diaphragms, and stuff like that. Handy tool.

Bernie

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6 hours ago, Red Riviera Bob said:

Taking the O ring off the single master cylinder and reinstalling on the new dual master cylinder. I’ll keep the forum aprised of progress.

Red Riviera Bob

Putting the ‘square O ring on solved the problem. Thanks to all for the help.

RRB

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6 hours ago, 60FlatTop said:

 

Dewey rebuilt and cad plated my "60 booster quite a few years ago. I was happy with the service.

 

"Defective hose" is interesting. Vacuum and fuel hose diameters have changed over the past few years and most come on an external MM size, yet marked fractional per the ID. I had a hell of a time with the Corbin clamps on my fuel lines last time I worked on the '60. The OD of the 5/16" lines is just a bit smaller and the clamps won't clamp. I bought about 20' of fresh and ended up digging out a length that is probably 15-20 years old to get things the way  way I wanted with the original clamps. It is possible something like that happened.

 

As I read the first few comments I wondered why vacuum had not been applied as part of the original diagnosis. I have a couple of MyTeeVac hand vacuum pumps with a bunch of hoses and fittings that I use fairly often. They are real handy for verifying hoses, connectors, diaphragms, and stuff like that. Handy tool.

Bernie

The Mighty Vac hand held tool is a great tool. The first time I tried to use it I had no vacuum on every line I tested. It took awhile before I saw the tool had two settings. If you want to measure vacuum the tool has to be set on vacuum.

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