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kks_john

411 front brakes lock up gradually...

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alright, I have rebuilt the cylinders. new seals at least, cleaned everything real good and put it back together.

 

basically, when I drive the car, it is fine at first but then the front brakes start to drag and eventually lock up. I can get out and bleed them and they will work just fine for a while more, then the same thing.

 

The only solution I have been able to come up with so far it to keep air in the front lines. this seems to cushion the lines and slows down the process of lock-up.

 

None of the cylinders leak anymore. and no you cannot adjust the front brakes, there are two cylinders that run in series.

 

thanks

-John-

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ive never had problems with my front brakes on mine so i cant help but im converting mine to disc at mo

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i assume drum brakes as you talk about wheel cylinders. how old is the spring kit? you might have one or more that have lost tension. i have had this happen before on an old dodge. mostly rear though as that is where teh ebrake is. BUT it never hurts to look into the possibility. also its weird that there is no adjustment for the front. dual wheel cyls PER drum? post a pic so we can see how its set up and maybe someone would think of something else.

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The push rod from the pedal to the M/C needs to be adjusted. Needs more slack so the piston can return and let the fluid back into the reservoir. It isn't returning to it's rest position and residual pressure is trapped in the system. Each time you use the brakes a little more is added till the brakes seize.

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oh man, I hope it is that simple. I didn't even think to check that. thanks!

 

yes, two cylinders per wheel, one for each shoe. kind of cool actually.

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I agree with datzenmike that this is the most likely problem and is the first thing that need checked. One other thing that i have seen cause this is old rubber brake lines. As the inner liner starts to break down the inner hose can collapse and make like a check valve, only allowing fluid to flow in one direction or only under pressure(pedal applied), but restricted enough to not release the brakes.

 

Jason

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Heard of that too. One for the books.

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dual wheel cyls PER drum? post a pic so we can see how its set up and maybe someone would think of something else.

 

411frontdrumbrake.jpg

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I agree with the other posters that there is constant pressure on the master cylinder that is causing the brakes to lock. I had the same thing happen to my clutch m/c, which would cause the clutch to disengage as the pressure built.

 

HOWEVER, I disagree when you say the front brakes are not adjustable. You do not adjust the wheel cylinders, but you do adjust the graduated peg that goes between the shoes. Turning this takes up slack due to worn shoes and/or drums.

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In the picture posted the shoe adjuster is part number 48. There will be another one for the other shoe also. What is the description of this part from the book??

 

Jason

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Ok, I may have been wrong about the location and style of the adjuster, but I stick by my original assertion that there is one. Just been a long time since I worked on a PL411... I'm trying (and failing) to find a diagram or picture of the brakes online, but my next memory tells me there is an offset peg that goes through a hole in the shoe that is used to move it closer to the drum. Can someone confirm if I am correct?

 

the front brakes on a 411 do not have this peg. the shoe sits on the cylinder on one end and the back of the second cylinder on the other end.

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Ok, I may have been wrong about the location and style of the adjuster, but I stick by my original assertion that there is one. Just been a long time since I worked on a PL411... I'm trying (and failing) to find a diagram or picture of the brakes online, but my next memory tells me there is an offset peg that goes through a hole in the shoe that is used to move it closer to the drum. Can someone confirm if I am correct?

 

The offset peg is pictured above as part 48.

 

Jason

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Thanks. I failed to mention that most picture sites are blocked by my work so I could not see the diagram. Now that I'm home I can see it and yes, that's what I was (next) remembering.

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In the picture posted the shoe adjuster is part number 48. There will be another one for the other shoe also. What is the description of this part from the book??

 

The parts manual lists it as CAM-shoe adjusting.

 

I need to get a decent scanner. The pic in the service manual is much clearer.

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