'41 Hydraulic Brakes

usered

usered

Senior Member
I've put "41 hydraulic brakes on a Model A frame. Mounted the single master cylinder to the frame under the body and used 3/16 brake lines.

I've adjusted the brakes (many times) and have a pretty good patter of use on the shoes to the drums.

Problem is the brakes have always felt soft. Never have been able to lock them up.

I'm wondering if the I should have used 1/4 brake lines on the old single master cylinder?

Options would be to convert to dual master cylinder would be safer but room for it becomes an issue or convert the lines to 1/4.

Any thoughts on this, is this the problem?
 
This system requires 1/4" lines. That's what it was when designed. How did you get 3/16" lines to fit any cylinders?
 
Diameter of brake lines or type of master cylinder has nothing to do with soft pedal. Soft pedal is likely due to shoes not fitting drums perfectly. MC under the floor also makes bleeding more difficult. Put some bendix brakes on and you won't have any trouble with a soft pedal because they are way easier to adjust.
 
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The 1/4" line will move more fluid
but regardless of the tubing size the pedal should be hard.
The smaller line requires more pedal travel to move the amount of fluid to move those big wheel cylinders but other than a lower pedal the pedal should be hard.
I would recheck the shoe adjustment with 8 adjusters you need to have them right .
The other thing is if the master is mounted under the floor consider putting residual valves on the front and rear they stop the fluid from draining back into the master and hold a small amount of pressure in the line.


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The line size shouldn't be your problem creating the soft pedal. With either size the line is full before and after you apply the brakes. I run all 1/4 lines because that is how the system was designed and I don't think I am smart enough to second guess the engineers that designed it. Any chance you are getting flex in your master cylinder mounting bracket and that is causing your soft pedal feeling? How about some pictures of your master cylinder mount? Are you using silicon brake fluid (which traps air and causes a soft pedal)?

Charlie Stephens
 
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Any chance your drums are way oversize (over .060) and what you are feeling is the drum flexing?

Charlie Stephens
 
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mrtexas said:
Diameter of brake lines or type of master cylinder has nothing to do with soft pedal. Soft pedal is likely due to shoes not fitting drums perfectly. MC under the floor also makes bleeding more difficult. Put some bendix brakes on and you won't have any trouble with a soft pedal.
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I agree with you that the Bendix brakes are much better than Lockheed brakes but I don't think changing will solve the soft pedal problem. The soft pedal is somewhere other than the type of brakes. I have never heard "spongy" as a characteristic of Lockheed brakes.

Charlie Stephens
 
Bleeding the brake system with the master under the floor is best done with a pressure bleeder. Otherwise it will take a very large amount of fluid and lots of "pump and hold" to get all the air out of the system. If you are using DOT5 (silicone) fluid), instead of DOT3, getting a "hard" pedal will be very difficult. I'd take the car to a shop with a pressure bleeder to finish the job.
 
If you bought new modern offshore production wheel cylinders did you take them apart first to see if they were mace correct---I have seeen many that the bleeder passage was not drilled to the top of the cylinder so trapped air can escape----some the hole is as much as 1/3 the way down from the top ---no matter how much bleeding you do you can't get the air out

If rebuilt they have to be taken apart and inspected too----the last several times I was supplyed with rebuilt cylinders from one of the places that advertizes a lot I learned to take them apart and wash out the brass shavings stuck in the rubber cups
 
supereal said:
Bleeding the brake system with the master under the floor is best done with a pressure bleeder. Otherwise it will take a very large amount of fluid and lots of "pump and hold" to get all the air out of the system. If you are using DOT5 (silicone) fluid), instead of DOT3, getting a "hard" pedal will be very difficult. I'd take the car to a shop with a pressure bleeder to finish the job.
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I have found all of above to be true. However, I have installed "Speed-Bleeders" on my '51 (which has the master under the floor) and I had no problem at all bleeding it by myself. Granted, I was just flushing the system to fill it with fresh fluid, but I moved a lot of fluid with little trouble. It may be different with a new fill of a fresh system, but I will never have another car without "Speed-Bleeders".
 
usered said:
....Problem is the brakes have always felt soft. Never have been able to lock them up.

I'm wondering if the I should have used 1/4 brake lines on the old single master cylinder?

Options would be to convert to dual master cylinder would be safer but room for it becomes an issue or convert the lines to 1/4.
.....
Click to expand...

The 3/16" lines and single (vs Dual) master cylinder are not the cause of your problem. Posters have provided some good ideas on what to look for. We'd all like to hear how you solve the problem.
 
Thanks everyone for the feed back I will follow up on a couple of ideas you had. At least I know now that the lines aren't the problem.

Let you know what I find out.
 
Roger W Gerow said:
Just a thought. If you installed ;new lining without having it arched to the drums, that might be an issue.
Click to expand...

Same thought occurred to me. Arching shoes to drums is an important step to a good brake job, that is overlooked because arching machines are not that common anymore.
 
This is one way shoes are ground to fit the drum-(Barrett Brake Doktor)---this does it on the car and centers the shoes at the same time, a adjusting tool is fit into the drum and the tool is adjusted to cut for a perfect fit

the other machine the shoe is put in a fixture, the drum diameter is dialed in and a sanding drum cuts the lining to the diameter of the drum-----then on a 41 the lower pivots have to be used to center the shoes
 

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Arching brake shoes to fit the drum use to be one of the very important steps to a good brake job. In some cases the linings could be ground to fit the drum, however, if the shoe was badly out of round the shoe had to be re-arched to fit the drum prior to grinding the linings.
It became a no,no to grind/arch linings over thirty years ago with the asbestos scare that became so common.
It is very common to have problems with '39-41 brakes because of the difficulty of adjusting the lower adjusters which center the shoes within the drum. Ford had a specific tool for this purpose. Some mechanics made their own tool by cutting away the face of a drum which allowed the modified drum to be mounted to the axle, then the adjustment could be checked with a feeler gauge.. Very fool proof if you have a spare drum to sacrifice, of course it requires both a front and rear.
I changed my brakes from '41 to '42-48 just to eliminate the adjusting problem..
 
Barnfind08 in post 2 got it right; while there may be still be other problems; 3/16" lines and Lockheed brakes do not get along.

It's about flow and feel; not about pressure being equal thru-out the system once the brakes are applied.
 
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