Brake Problem

[Red63440]

Last year I converted my 1964 Fury to disk brakes. To do this I had to change from a single pot master cylinder to the new dual pot master cylinder and also changed the lines and distribution block to split the front and rear brakes. Everything has been installed and all bled but now I have to stand on the pedal to even get the car to slow up at idle. The factory booster doesn’t seem to be working at all now and I’m at a loss as to what to do. I don’t want to send the booster out for rebuild if it’s not the problem. If I clamp off the vacuum line to the booster I get a hard pedal, removing the clamp from the vacuum line allows the pedal to go about half way to the floor but the brakes don't work any better. If someone sees something I did wrong please speak up,

Thank you

 

[Jerry Hall]

What is the bore size on the master cylinder?

 

[Red63440]

1 1/16”, it’s the master cylinder supplied with the disk brake kit from Leed and designed to work with the factory booster.

 

[BeepBeepRR]

Dual diaphragm booster?

Bought this for the road runner. It was a drum drum car put a front disc kit on but the new booster quickly failed.

Bought one of these from pirate jack and no problems since.

Bendix Style Mopar 1966-1970 B Body Power Brake Booster Conversion Kit BCK8536-1 OEM Style for 1966-70 Charger, GTX, Road Runner, Satellite

Shop Pirate Jack for disc brake conversion kits, master cylinders, brake boosters and much more. We carry parts for Fords and GM made vehicles.

piratejack.net

 

[Don Frelier]

I mentioned it to my son. He suggests bench bleeding the master cylinder.
I've been able to replace them and just leave the lines a little loose pump the brakes slightly once or twice and tighten them back up on the master.
If that is successful you don't even need to bleed the system.

 

[Red63440]

The original master cylinder that came with the kit proved to be faulty. I returned it to Leed and they bench bled the replacement so it’s already been done. When I picked up the replacement master cylinder was full of fluid, and the outlets were capped.

 

[Red63440]

Dual diaphragm booster?

Bought this for the road runner. It was a drum drum car put a front disc kit on but the new booster quickly failed.

Bought one of these from pirate jack and no problems since.

http://[URL]https://piratejack.net/mopar-1966-1970-b-body-booster-conversion-kit/

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It’s on a 1964 Fury so I’m sure it’s a Midland booster.

 

[Don Frelier]

The original master cylinder that came with the kit proved to be faulty. I returned it to Leed and they bench bled the replacement so it’s already been done. When I picked up the replacement master cylinder was full of fluid, and the outlets were capped.

Just because they claim to have done it...
If I do it myself it removes the question mark.
You could maybe make some lines and jumper them back up into the reservior and do it in the car.
It might show you something as well.
Just some ideas.

 

[Ron H]

The ‘new’ booster and especially the MC were suspect with my conversion hassles. There are 3 checks I’m aware of to test the booster using a pump vac gauge and they indicated it was fine. Upon BB the MC, one reservoir wouldn’t end bubbling after a bunch of tries, replaced it. I had tried bleeding it in the car then back off on the bench. I believe, if you maybe haven’t done it, is re-bleed the brake system after installing the new MC as the lines have the chance to get air in them reconnecting them.

My car has a mild cam and the required vacuum is right around the border line of what’s needed so installed a reserve canister for extra measure. My setup requires an 8” dual booster. Hard pedal can, not always, indicate there might be air trapped in the system. Elementary thing is the caliper bleeders being on the top. Inspect the gap btw the booster rod and MC also assure that the rod is pushing the piston sufficiently complete. Another check, with a helper is to watch the action of the calipers/pads while the helper presses the pedal. Hold the pedal and see if the rotor can still be turned by hand. Include assuring the pads aren’t cocking/binding. Had this hassle once.

There’s a bunch of possible gremlins including the rear drums being adjusted, line condition, and in my case the drums were old and maxed-worn replacing them along the route of killing the gremlins.

Stuff you may know about, related or not, just tossing some of this out recollecting my conversion.

 

[Red63440]

Thanks for the input…front disks are operating properly, bleeders on the top. Rear drums are new and adjusted properly. All lines are new except one and fluid flows easily. Cam is just slightly larger than a 383 magnum cam so I don’t believe there is a problem there. Vacuum line is off the intake where it was before all of this started. This just has me totally frustrated…..!

 

[Ron H]

This just has me totally frustrated

I know - I feel your pain. Best of luck on the hunt.

 

[Red63440]

More brain cells die every day, pretty soon I’ll just be totally stupid.

 

[Red63440]

Who are the booster rebuilders that people trust to do a good job at a reasonable price?

 

[dvw]

If removing vacuum fom the booster changes the pedal fell it is doing something. The booster should hold vacuum over a period of time. after the engine has been run let it set. Then pull the check valve out of the booster. You should hear air rush in. If you don't its leaking. You also state you are not getting much fluid from one line. Which Line? I just did a manual disc conversion on a 68 Satellite fo a customer. The factory rear drum brakes were untouched and in good shape. It had a hard pedal with very poor stopping power. The issue turned out to be 2 causes. The master cylinder bore was the wrong size (to big). We went down to a 1" bore. Second the rear flex line was restricted allowing very little fluid flow to the rear brakes. With the wheels in the air have someone apply light pedal pressure. Can you rotate any of the wheels?
Doug

 

[Red63440]

Doug, I replaced all the lines except the line that runs to the rear brakes inside the frame. Car is from the west coast and line is very good, all other lines and hoses are new. New disk brake conversion on the front, new drums and 90% shoes on the rear. Master is 1” or 1 1/16” bore mounted on the factory Midland booster, master cylinder is made to work with the conversion kit and is a C body master for power brakes and is also new. When booster is connected pedal goes 1/2 way to the floor and you have to stand on the pedal to stop the car. When the vacuum is disconnected from the booster pedal is hard and you still have to stand on the pedal to stop the car. The cam in the engine is an Elgin and just slightly larger than a factory magnum cam. Vacuum is drawn from the intake manifold. When the car is up on jackstands when you step on the pedal, the wheels stop.

 

[Don Frelier]

When we moved the car last week I thought the pedal should be higher and harder with the booster disconnected.
It did have some mushiness when I pressed hard on it.
But then again I've never been in your car before...

For comparison:
If I roll my Plymouth down my driveway without running the engine (which has a pretty good grade downhill) I need to press on the brake pedal pretty firmly.
It will stop just not real easily.
When running it stops with little pedal effort.

 

[Red63440]

Other than the position of the pedal the car is hard to stop running or not….maybe I just need to throw out an anchor!

 

[BeepBeepRR]

Do a peddle test.. Sit in the car with the engine off. Push the brake peddle in till you cant any more. Then fire up the car and see if the peddle drops further. If so the booster is working. If it pushes back its possible you have an internal leak.

 

[Jerry Hall]

It concerns me that you have a hard petal without the booster. In a non assisted brake system that indicates a internally clasped line, usually the rear line. Try what @BeepBeepRR indicated. I don't ever change just one line, but do all three. They can look very good, but still be bad.
As for bore size, a 1" bore usually does both power and non power systems, but I don't think the extra 1/16" makes much difference.

 

[Red63440]

I made a call to John at Leed and asked him a few questions. The booster is good but the adjustable valve for the rear brakes was turned all the way out which means the flow of fluid to the rear brakes was reduced by 55%. I reattached the vacuum line to the booster and did the pedal drop test and the booster is good. Took it for a spin around the block and it runs great although a little noisy….head pipes and inspection is next. Thanks for all the input!!