Juice brake problems

[denver9]

I have hydraulic brakes on my 31 Town Sedan. They were installed by the previous owner several years ago.
The brakes have always worked really well until the vehicle sat for a period of time. Recently, we went on an extended vacation and the car was parked for at least six weeks.
Upon our return I started the car and began to back it out of the garage. to my surprise, the brake pedal went all the way to the floor when first applied.
I pumped the pedal several times and the pedal came back to normal and the brakes work fine. After sitting for a couple of days the brakes are still normal.
My guess is that the master cylinder slowly allowed the fluid to leak past the cylinder, normalizing the pressure on each side of the piston.
I am considering replacing the Master cylinder with a dual reservoir unit (the current one is a single cylinder model.)
What are your thoughts on this? Is my diagnosis correct?

[Purdy Swoft]

If you keep the hydraulic brakes, the battery box style master cylinder would be a good choice.

[flatford39]

sounds right...do you see any sign at all of leakage??? When you speak of dual reservoir are you segregating your rear brakes from the fronts?? You may also need to install a proportioning valve. Not sure you need a dual reservoir on a car as light as a Model A.

[34Fordtk]

In my experiance if you can hold your foot on the pedal (with pressure) like you are stopping and it goes to the floor slowly its the master or a leak somewhere in the system.

[Russ/40]

It's hard to say what happened, but you need more observation to narrow it down. You did not say if the fluid level is down. Have you been paying attention to the fluid level? Any sign of leaking at the master cylinder or at the bottom of any of the backing plates? These areas are supposed to be dry.

I had a similar thing happen. I got in the car, and the pedal went to the floor. I checked the fluid level and it was empty. Checked the garage floor and all the fluid was on the floor under the master. All wheel cylinders were leak free. The entire leak was past the master cylinder cup. I refilled the master, and the problem never showed again. That was ten years ago. I use silicon DOT5, and I suspect there was some particle that ended in the wrong place and allowed the leak over an extended period of time, until it went dry.

[Tom Wesenberg]

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First choice is to go back to mechanical brakes.

If you stick with juice brakes, then flush the complete system and use DOT5 silicone brake fluid. Also hone the cylinders and replace the rubber cups as needed before installing the new fluid.

[denver9]

I have no intention of going back to mechanical. there is a lot of controvery on that subject and I believe it is a matter of opinion and choice. I would not bad mouth either choice but I prefer hydraulic. I agree that the battery box mounted master cylinder is a good choice if one has room. On my coupe, I could not use it because I also am running a Chevy S-10 tranny (5 speed with O.D.) and love it. unfortunately it leaves no room for the battery box mounted cylinder.
My sedan has a 39 ford tranny so not sure if it leaves room or not. Will have to check it out. Thanks for the suggestion.

[denver9]

It is my understanding that a dual reservoir allow 1 system to fail while leaving the other system intact. That is the only reason I am considering a dual reservoir.

[denver9]

Originally Posted by flatford39

sounds right...do you see any sign at all of leakage??? When you speak of dual reservoir are you segregating your rear brakes from the fronts?? You may also need to install a proportioning valve. Not sure you need a dual reservoir on a car as light as a Model A.

When I did the hydraulic conversion on my coupe, I installed a proportioning valve. After the first use the brakes locked up. come to find out, the new master cylinder has a built in proportioning valve and the two were working against each other. I removed the external proportioning valve and all was well. The supply house for the master cylinder told me that most new master cylinders have a built in proportioning valve. don't know if that is a fact or not, but something to consider when doing a hydraulic conversion.

[Pete]

If you use a Wilwood dual master cylinder and associated linkage, it has a built in balance bar to easily adjust the front/rear bias without using a proportioning valve.

[denis4x4]

There's a very easy, inexpensive fix that uses the brake cross piece. As you can see in the photo, I'm running a T-5 and the master cylinder is mounted under the passenger side floor board for easy access. I even cut down a brake rod to connect to the MC. In fact, I used existing holes to mount the MC on the crossmember. I threw in a second photo showing how the crossmember was reinforced before somebody makes a comment of cutting an A crossmember for a T5 installation

After reading many of the posts here pointing out that mechanical brakes are far superior to hydraulics, I starting having a complex. After twenty plus years of driving A's with hydraulics, I don't have rusted lines, burst hoses, leaky wheel cylinders or bad master cylinders.

One of the mechanical brake gurus out there needs to tell me what I'm doing wrong!

[Pete]

Originally Posted by denis4x4

There's a very easy, inexpensive fix that uses the brake cross piece. As you can see in the photo, I'm running a T-5 and the master cylinder is mounted under the passenger side floor board for easy access. I even cut down a brake rod to connect to the MC. In fact, I used existing holes to mount the MC on the crossmember. I threw in a second photo showing how the crossmember was reinforced before somebody makes a comment of cutting an A crossmember for a T5 installation

After reading many of the posts here pointing out that mechanical brakes are far superior to hydraulics, I starting having a complex. After twenty plus years of driving A's with hydraulics, I don't have rusted lines, burst hoses, leaky wheel cylinders or bad master cylinders.
One of the mechanical brake gurus out there needs to tell me what I'm doing wrong!

I had to think about it for a minute, wondering why you had to notch the cross member so much but you must have used the standard store bought adapter. I have never had to notch the cross member more than 1/8 inch but I use a home made adapter to take a Chev bell housing.
Much cheaper that way and I can use a Lakewood scatter shield for race applications.

On the brake issue, I have never had any problems with juice brakes
in the 65 years I have been putting them on hot rods so I guess that makes 2 of us that have been doing it wrong.

[V4F]

i was told to put a "residual" valve in mine to keep it from draining back . seems to work fine . it is between the m/c & the "T" fitting that splits the lines & stop lite switch .

[A bones]

My two pennies... If the pedal pumps up fluid is leaving and air is entering some where in the system; such as: fitting, line coupler, and most commonly wheel cylinder cups. On the other hand if the pedal pumps down or drops while holding pressure on it, the master is bad. Also worth saying is, more times than not when a hydraulic system leaks the leak is found at the wheel cylinder. The cause of this is multi-fold: collection of dirt in the cylinder, heat from shoe lining friction, moisture (corrosion) from roadway and temp change, and a lot more vibration than the master.

[denver9]

[QUOTE=denis4x4;909832]There's a very easy, inexpensive fix that uses the brake cross piece. As you can see in the photo, I'm running a T-5 and the master cylinder is mounted under the passenger side floor board for easy access. I even cut down a brake rod to connect to the MC. In fact, I used existing holes to mount the MC on the crossmember. I threw in a second photo showing how the crossmember was reinforced before somebody makes a comment of cutting an A crossmember for a T5 installation


I used the same method of mounting the master cylinder in my coupe (with the T-5) and it works well. The only caution I would add is the master cylinder needs to be shielded from muffler heat. Other than that, I have had no problems.

[chiliman]

I have Dave wiltons Batery box running f-100 trans have enough room works great

[JOES31]

Originally Posted by denver9

It is my understanding that a dual reservoir allow 1 system to fail while leaving the other system intact. That is the only reason I am considering a dual reservoir.

denver9

You are correct. The dual reservoir is a fail safe system and I would not have hydraulic brakes without one. I have mechanical brakes on the Tudor and will not change them to hydraulic. Mostly because I want to keep it original and I basically don't drive that fast where it would make a big difference. Let's make no mistake about it. Hydraulic brakes are better stop faster and above all much safer. With the technology used on hydraulic brakes there is no comparison. Ceramic rotors are now employed in auto racing for their superior heat dissipation and elimination of rotors warping.

Mechanical vs Hydraulic....no comparison.

[denver9]

Chilliman:
I removed the floorboards to get access to the master cylinder (Previous owner should have cut an access hole in the floorboard). While there I took a look at the battery area to see if I would have room for the battery box mounted M/C. As it turns out, the linkage for the Mitchell Overdrive takes up a good portion of that real estate, so that rules out the battery box. The master cylinder is mounted on the passenger side and seems to work fine there.
In response to someone else's comment, I checked the fluid level in the M/C and it was OK. The left rear wheel looked a bit suspect so I removed the drum to inspect. There was no evidence of fluid leak at the wheel cylinder cups. However, there was an inordinate about of brake shoe dust and grime scattered about (Maybe the brakes had been adjusted too tight?)
Thanks EVERYONE for your many responses, they were helpful.
At this point, I think I will just flush the brake lines, clean everything up and see what happens. Will do the dual reservoir cylinder IF and WHEN the existing master cylinder fails. If it ain't broke, why fix it??

[Pete]

"Will do the dual reservoir cylinder IF and WHEN the existing master cylinder fails. If it ain't broke, why fix it??"

Yeah, don't forget, sprint cars and midgets only have one master cylinder and they go over 100 mph twice a lap with the discs glowing red.

[Bruskie]

If your shoes are not adjusted up properly over time the spring tension will slowly pull them back and force the fluid back into the master. This is a common problem with the master mounted under the floor with drum brakes. this isn't an issue with disc brakes