power brake issue

[steve from staten island]

I have installed my front disc brake conversion kit. I cannot safely stop the car, the brakes wont lock up and take a lot of pedal effort. Im thinking my booster which was rebuilt by a shop on the West coast known for booster work, it is not working
How hard should it be to stop a car if the power booster is not working? I took the master off and it seems the rod is adjusted properly. I have vacuum to the check valve. When i take the check valve on and off with the car running and look inside at the diaphragm i see know difference, no movement. Even before the conversion the brakes didn't feel right as far as the pedal. Any thoughts or suggestions are appreciated.

 

[rumcustom]

After running the car and then shutting it off, when you remove the check valve from the booster do you hear a vacuum sound? If not the check valve is not working properly. Are you sure you bled the brakes completely? Lastly, this is an SSBC kit right? I have had good and bad experiences with SSBC. Mostly good but at least two bad. Both times the master cylinder was not sized properly.

 

[69L48Z27]

Put your foot on the brake pedal and start the car, if you feel your foot fall a little when the car starts the booster should be working.

Do you have a hard or soft pedal when try to panic brake?

 

[steve from staten island]

Yes its a SSBC kit. I was not to impressed with the tech either. He was somewhat dismissive and asserted i may not have properly bed in the brakes. I told him i backed the car out of the driveway and drove up and down the street. How can i bed the front discs in if the car wont stop safely at 25 MPH. The master cylinder looking at it, i would think its the proper size. Its the same size reservoir wise as older cars with front discs i had way back when. Im going to check out the booster as you said and thanks

 

[steve from staten island]

Put your foot on the brake pedal and start the car, if you feel your foot fall a little when the car starts the booster should be working.

Do you have a hard or soft pedal when try to panic brake?

It feels hard but requires a lot of effort to stop, way more than a older car with power brakes

 

[69L48Z27]

If they were not bled I would think the high and hard pedal would not be. Soft pedal going to the floor is usually a bleed problem.

Sizing the MC is the bore not the reservoirs.

For instance:
Manual brake in relay any disc combo is 15/16".
Power Disc/Disc is 1"
Power Disc/Drum is 1-1 1/16"
Not sure what Drum/Drum is. Maybe up to 1 1/8".

 

[Fran Blacker]

Is the hose from the intake collapsing ?

 

[WileERobby]

Manual brakes have more leverage engineered into the pedal system. The booster assists the power applied,so without the boost, that's why you feel the difficulty on the pedal. Off the top of my head, I'd say it's either the booster or the check valve

 

[rumcustom]

If they were not bled I would think the high and hard pedal would not be. Soft pedal going to the floor is usually a bleed problem.

Sizing the MC is the bore not the reservoirs.

For instance:
Manual brake in relay any disc combo is 15/16".
Power Disc/Disc is 1"
Power Disc/Drum is 1-1 1/16"
Not sure what Drum/Drum is. Maybe up to 1 1/8".

69L48Z27 is correct. It’s not how the master cylinder looks from the outside, it’s the size of the piston bore. I know the master cylinders in the kits might be shiny new and look like they’re worth trying to keep, but I suggest you get your hands on a stock power disc brake master cylinder and give that a try.

 

[rumcustom]

69L48Z27 is correct. It’s not how the master cylinder looks from the outside, it’s the size of the piston bore. I know the master cylinders in the kits might be shiny new and look like they’re worth trying to keep, but I suggest you get your hands on a stock power disc brake master cylinder and give that a try.

As others have said, test the booster first. That’s free. After you rule out the booster operation, and if the brakes are fully bled, all signs point to the master cylinder.

 

[steve from staten island]

What i found out is when i start the car with my foot on the brake there is no movement, i thought there was the other day but not just now and i tried it a few times. When i shut the engine off and pump the pedal i hear no vacuum noise. With the engine running i can hold my finger over the check valve and it gets sucked in. I can put the check valve into the booster and remove it and i vacuum sucks out but when i shut the car off and try and release the vacuum immediately there is no vacuum. I dont think the booster is working.

 

[rumcustom]

What i found out is when i start the car with my foot on the brake there is no movement, i thought there was the other day but not just now and i tried it a few times. When i shut the engine off and pump the pedal i hear no vacuum noise. With the engine running i can hold my finger over the check valve and it gets sucked in. I can put the check valve into the booster and remove it and i vacuum sucks out but when i shut the car off and try and release the vacuum immediately there is no vacuum. I dont think the booster is working.

That’s right. The booster is leaking. Diaphragm is shot. Needs to be replaced.

 

[rumcustom]

That’s right. The booster is leaking. Diaphragm is shot. Needs to be replaced.

Did u say you verified the check valve is good? If not verify that first before replacing booster.

 

[steve from staten island]

Did u say you verified the check valve is good? If not verify that first before replacing booster.

I held my finger over it with the engine running and it had vacuum. The booster is new and was redone by a outfit in Oregon....
Were the master goes against the booster, there is a sort of spacer could there be a leak there

 

[rumcustom]

I held my finger over it with the engine running and it had vacuum. The booster is new and was redone by a outfit in Oregon....
Were the master goes against the booster, there is a sort of spacer could there be a leak there

With the engine running it it’s supposed to pull a vacuum though the check valve like you said. When your engine is shut off (vacuum drops) the check valve should close to hold the vacuum inside the booster.

 

[steve from staten island]

With the engine running it it’s supposed to pull a vacuum though the check valve like you said. When your engine is shut off (vacuum drops) the check valve should close to hold the vacuum inside the booster.

Its not doing that as i think its leaking somewhere. Were the master bolts to booster there is a gasket/spacer could it leak there? Thank you for your help i appreciate it

 

[moparnation74]

Sounds like a diaphragm or a seal leak.......

Did you send it to Booster Dewey?

 

[steve from staten island]

Sounds like a diaphragm or a seal leak.......

Did you send it to Booster Dewey?

Yes Justin i did. I dont want to believe this new booster is defective, not when Dewey rebuilt it. I used then for just this exact reason of not wanting to remove it once installed . Im out of ideas as far as this problem but it sure looks like the booster is not working properly
The brakes never felt right from the get go and i did have that front wheel cylinder leak before i did the conversion. I will say they did lock up when they were all drums but required a lot of leg pressure. Something is not right and thanks for the help

 

[69L48Z27]

The only test left would be to use a hand vacuum pump with a gauge. Pump it up and if it does not hold then it needs to come out for sure.

 

[Sixpactogo]

Steve, If you are using the stock booster that was on the car originally, that is part of your problem. (if not all of the problem) It is a single ballast booster and you need the dual ballast booster when you upgrade to front discs. I went down that same road with my 68 Charger. Had the booster rebuilt, upgraded to discs and the brakes would not stop the car. I spoke with Cass at Dr. Differential who told me I needed the dual ballast booster. Once I got that problem fixed, I have excellent brakes.