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Expert
Posts: 1508
 
Location: new york | Hey guys , I have owned lots of 57-9 Plys over the past 30 or so years. We are doing a new system on my convertible and cannot get a pedal. And when we get it its not solid. I bought 6 wheel clys and master all hoses and now all new steel lines and still not right. We even change to a dual master, and still not right. Is it the new parts are just not right? I bought everything from Bernbaum and have not had issues in the past with his parts. The dual master was from NAPA. Is any one else having these problems? |
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Expert
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Location: Chestertown, NY ( near Lake George) | Low pedal, drops, spongy, what is the exact condition? |
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Walter passed away on Jul 29, 2014. We will miss you, Walt!
Posts: 5358
Location: Heaven Above (Formerly Oklahoma City,OK) | Bench bleed the master cylinder. Istall it on the car and then bleed the wheel cylindars starting on the right rear, left rear, right front and then left front. You'll need to bleed both cylinder on the front brakes,
and you'll probably need to adjust the brakes on all wheels before trying to bleed them. That what I've had to do. . . . . . . |
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Expert 5K+
Posts: 8454
Location: Perth Australia | I am curious about the dual circuit master.
I was told by someone that you could not use a dual circuit one on a 6 slave cylinder car because it does not move the fluid properly.
How did you set yours up as I want to use dual circuit brakes
Thanks
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Expert
Posts: 1324
Location: Hickory, NC | Make sure that you have bled the master. I usually mount the master on the car with the lines disconnected and put a plug in the outlet. Pump with my hand very lightly..not moving the cylinder more than a 1/2 inch or so...bubbles will flow out...keep pumping until there are no bubbles. I begin increasing the pedal travel when I cant get any more bubbles. Eventually the fluid will start spraying very strongly. Be careful not to have it shoot all over the car if you have the lid off!
Then connect the line. I adjust the shoes out so there is no travel. Pump the system with fluid...then begin bleeding from the wheel cylidner furthest away from the master working towards the closest. The bleeder screws should be at the top of the wheel cylinders.
I put a dual pot master on my '57 Plymouth with standard brakes...worked fine. I had to adjust the pushrod some if I remember correctly.
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Elite Veteran
Posts: 1090
Location: Auckland, New Zealand. | What is the correct procedure for adjusting the brake pushrod? The manual calls for between 1/32 & 1/8. But where is this measured exactly, since you cannot see where the pushrod contacts the piston in the master cylinder when it’s installed? |
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Exner Expert 10K+
Posts: 10395
Location: So. Cal | The amount listed there sounds like it is measured at the back of the master cylinder. But just check it from the play in the pedal. But you'll need more play than that, from there. Put it at about 3/8-1/2". If you don't have enough play, when the car gets hot, the brakes will always be applied. I found that out the hard way. My '58 Fireflite was dragging when it was really hot outside and the engine fully warm. Gave it more play and the problem went away. |
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Elite Veteran
Posts: 1090
Location: Auckland, New Zealand. | Yes but where exactly do you measure the clearance? Since the pushrod depresses a spring loaded/hydraulic piston, which you cannot see, how do you know when there is/isn't clearance between the end of the pushrod and the piston in the master cylinder?
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Elite Veteran
Posts: 745
Location: Finland | Are you sure you have the right version of the brake shoe return springs and that they are installed correctly? |
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Elite Veteran
Posts: 1090
Location: Auckland, New Zealand. | The question is about master cylinder pushrod clearance. Nothing to do with brake shoe return springs. |
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Expert
Posts: 3851
Location: NorCal | FURY - 2024-10-20 8:37 PM
Yes but where exactly do you measure the clearance? Since the pushrod depresses a spring loaded/hydraulic piston, which you cannot see, how do you know when there is/isn't clearance between the end of the pushrod and the piston in the master cylinder?
You should be able to depress the brake gently by hand and feel when the push rod hits the bottom of the cavity in the MC rear piston.
What is the diameter of your MC, a low soft pedal might simply be a MC that's undersized?
 (Pushrod Adjustment.gif)
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 Pushrod Adjustment.gif (27KB - 274 downloads)
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Exner Expert 10K+
Posts: 10395
Location: So. Cal | Exactly what I was going to say. Depressing it slowly by hand, you can tell when it hits the spring. |
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Elite Veteran
Posts: 1090
Location: Auckland, New Zealand. | Right with the pin that holds the brake pushrod to the brake lever arm removed, I was able to push on the pushrod using my fingers, and accurately feel when it was touching the back of the piston. (There is just no way to tell when it's touching or pushing the piston in with all the other brake linkage drag/brake return spring/power brake booster fork etc going on). Holding the pushrod there, I could then try to insert the pin back in, and I found that it would go in if the pushrod was withdrawn just a tiny amount from the piston. I had already backed off the pushrod about an 1/8 the other day, so perhaps that was what it needed. I'll see what happens after another decent drive. Thanks for the suggestions. |
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Elite Veteran
Posts: 1090
Location: Auckland, New Zealand. | Just when I thought that my pushrod adjustment might have solved my issues, I’ve now got a very weird problem.
I was noticing that my brake lights would be on randomly just sitting in the garage.
When I noticed they were on, I pumped the brake pedal a couple of times and they went off. An hour later they would be on again by themselves. Pump the pedal and they go off. Thinking I must have a faulty switch on the end of the master cylinder, I swapped it out with a new switch.
Last night, the brake lights had turned themselves on again. Pumped the pedal and they went off. Then an hour later they are on again.
What on earth could be causing this?
It obviously wasn’t the switch.
Since the switch operates by hydraulic pressure, what could be causing it to think there is pressure? |
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Elite Veteran
Posts: 745
Location: Finland | I would try to roll the car to see how much the brakes are applied . If it doesn`t feel at all I would consider swapping to a mechanical switch.
Probably the problem is in the dual master cylinder.. |
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Elite Veteran
Posts: 1090
Location: Auckland, New Zealand. | I jacked the car up and turned the wheels freely by hand. The brakes are not on, the hydraulic switch is just saying they are.
This is a factory single brake master cylinder, not a dual master..
I would rather fix the problem than start modifying the car because the problem can't be fixed. Not an option...
22mafeja - 2024-10-26 5:26 PM
I would try to roll the car to see how much the brakes are applied . If it doesn`t feel at all I would consider swapping to a mechanical switch.
Probably the problem is in the dual master cylinder.. |
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Exner Expert 10K+
Posts: 10395
Location: So. Cal | I've had that happen to me before, and it was caused by the hydraulic switch. When I switched to a mechanical switch, the problem went away. Unfortunately, those switches are really problematic. One caused a short that melted the wires on my '57 Windsor. I've had them short out on at least 6 different vehicles. Sometimes it's just best to move to a different solution. People say that they will last longer if you switch to Dot5 brake fluid. It's very possible that your new switch is bad, so you'll need to test it. If you want to test it, just unplug one line and run it through your multimeter to measure the current draw. Just make sure to use the 10 amp version so you don't blow your meter. Another option is to unplug both lines and measure the resistance across the connections. It should be infinite.
 (56Savoy Brake Light Leakage.jpg)
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56Savoy Brake Light Leakage.jpg (19KB - 250 downloads)
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Elite Veteran
Posts: 1090
Location: Auckland, New Zealand. | Thanks for the reply. While under the car yesterday I noticed a drop of brake fluid on the bottom of the light switch on the master cylinder.
I wiped it dry and a little while later a drop was again on the bottom of the brake switch.
So my brake switch is leaking. I have heard that Dot 4 brake fluid can cause this so I will swap the fluid out to Dot 3 and replace the switch again.
Edited by FURY 2024-10-26 8:12 PM
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57 Plymouth brake problems
