1950 Plymouth front brakes completely locking up HELP

[canadiandeluxe]

My old car has been giving me issues and locking up the front passenger wheel. I stopped driving it because of this and just had time to remove the drum to inspect if anything was broken or sticking really bad, I was thinking a broken return spring maybe. So I just cleaned it up and put it back together and drove it and thought it was fixed because it was braking normal but then after about 5 stops they went bad again and the front passenger wheel locked completely up after almost no pedal input and would not unlock until car had become completely stopped. I tested again and it kept doing it over and over no matter what speed I was going.

Any ideas guys? Nothing seems mechanically wrong. Would a bad cylinder cause this problem? A bad air pocket in my lines? Nothing seems physically wrong.

[Veemoney]

How old are your rubber brake hoses? They go bad over time on the inside and can plug the return brake fluid.

Edited September 5, 2022 by Veemoney

[canadiandeluxe]

As far as I am aware they could be original yet that could very well be the problem. Why would coming to a complete stop be the only thing that will release them though? I guess then the shoes aren't self engaging?

[Veemoney]

1 hour ago, canadiandeluxe said:

remove the drum to inspect if anything was broken or sticking really bad,

It could be once stopped it has time to seep some fluid back giving you just enough clearance to release the wheel till you brake again. 

 

I took it for granted when you said you checked for "broken or sticking really bad" issues that everything was observed moving freely before putting things back together. I should ask when you pulled the drum and did your inspection did you pull the rubber boots back on the wheel cylinders to see if they had rust inside or lightly actuate the brakes to see they were moving freely? Not sure what or how you checked to see if something was "sticking really bad" to rule that out but a rusty wheel cylinder with a sticking piston/s could also cause the issue. Air in the line would not cause it to lock-up.

 

If you haven't ruled out the wheel cylinders that would be my first guess as to the problem and then the brake hose after that.

[canadiandeluxe]

Ok I was thanking wheel cylinders but ya I had my gf actuate the brakes as I watched and they seemed free but I did not inspected the cylinders in detail and when I got the car running 2 years ago I never took the front cylinders off when I redid the back ones and master cylinder, which all got honed and new seals. That's where I will look next then. THANKS

[kencombs]

Master cylinder push rod adjustment is the first thing that comes to mind..  Or anything that doesn't allow the return ports to uncover when the pedal is released.

[greg g]

First thing to check is the release port in the bottom of the mc reservoir,  take the cap off and shine a light down so you can see the bottom through the fluid.  You should see two ports.  The small one let's fluid into the piston, the larger one relieves pressure when you release the brakes.  Take a piece of mechanics wire and clean out that port to assure fluid is returning to the reservoir.  There needs to be some room in the reservoir for fluid to return.  Second make sure there is about 1 1/2 inch of free play at the top of brake pedal travel before the linkage engages the piston.  Without freeplay, the sesidual valve can't release.

 

Thirdly, any brake fluid on the shoes will cause lockup.

[canadiandeluxe]

I will look into master cylinder too but I did not want to go to that right away since its only locking up the one wheel and like when I barely tough the pedal now but when it worked ok the pedal movement was as expected. I'm leaning to a bad hose or really stuck cylinder 

[Bob Ritter]

It might be time to consider disc brakes, I always had problems adjusting the front brakes on my 1938 Dodge it always seem to pull to the left, disc brakes was the answer to my problem.

[Harvie]

Hello Bob - what disc brake conversion kit did you use?

[canadiandeluxe]

Hey again guys I installed new hoses on my car all three of them for good measure. But I just fired her up and that passenger break will lock up no matter what. I barely touch the pedal and it's locked up on that corner. All other corners are operating fine. I even backed off the front shoe all the way and still just locks up no matter what speed. I think I'm going to try installed new cylinders but if that doesn't fix it any ideas?

[Dave72dt]

If the shoe liings are two different lengths, is it possible they are or can be installed incorrectly

[kencombs]

The most common cause of grabbing/locking brakes on even a light application has been contaminated linings, that's IME.   It doesn't take much brake fluid, differential oil or bearing grease to cause it.  Sometimes, a    good cleaning soak in alcohol can salvage an oily/greasy lining but not always. 

[Sniper]

THIS IS NOT THE CORRECT FORUM FOR THIS THREAD

 

This is the technical archive forum, where already answered stuff of technical value is saved.  As in it's a FAQ section.

 

Use the P15-D24 Forum instead