89 FS brake problem

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logansackett

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I have replaced everything at the left rear, I think the problem is the proportioning valve. Any way to test my theory? The valve is a dealer item only here in Co. so kind of expensive, can the valve be repaired, or maybe cleaned?

 

Dubl D

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The proportioning valve only has one line to the back of the truck, which tees and is fed to the left and right side evenly. When you say "binds", is this only when the brake is applied or does the brake start dragging?

 
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logansackett

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The proportioning valve only has one line to the back of the truck, which tees and is fed to the left and right side evenly. When you say "binds", is this only when the brake is applied or does the brake start dragging?
Dragging to the point of locking up the wheel.

 
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logansackett

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Have you done any adjusting to parking brakes?
None, can it cause the drag? I ask because it does not start out binding, I can sometimes make several miles before it starts to drag. It feels like it is related to use of the brakes, the more use the quicker it starts to drag.

 

Bronc76

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Did you replace wheel cylinder too? I think sometimes the piston can stick.

 

50joe

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Do you think its possible that the line itself got pinched/kinked, or perhaps something got in it not allowing the fluid to return properly on that side? Thats the way its sounding. BTW, is this a new problem, or something you were trying to fix before?

 

Chrish_jr

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for front brakes:

Sometimes with rubber lines when they get older they start to develope a "funnel" effect. Some show more drastic than others. basically, the line would only alow fluid to move in one direction or be restricted in one direction while allowing the brake pads to fully engage. Cant begin to tell you the number of cars I have helped friends with that had this issue and sadly, its highly overlooked. I'm not saying that this is your problem for sure, but may be worth checking into.

To check this, take the rubber line off and blow through it to get all the fluid out. then blow through it again to see if the air moves freely, then turn it around the blow into the opposite end. If its easy for the air to move one way but difficult the other direction, just replace the hose and it should clear up your problem.

As for the rear:

Make sure everything is put together correctly. Sometimes it can be as simple as just the self adjuster cable and adjuster itself was installed backwards so that each time you hit the brakes driving forward it would tighten up the brake shoes. Generally, the only time the adjuster should be moved on its own with everything attached is while backing up slowly, this is why you may at times hear a "click" sound every so often in the rear wheels. Could be the new cylinder had an issue and wasnt assembled correctly (pretty common from the orange parts store). Check to make sure the lines are working correctly and theres no obstruction of fluid travel. At times I've seen an air pocket cause the same thing but not a common cause.

 
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logansackett

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This was my first time working on drum brakes, so when I was done I took the bronco to brakes plus to have my work checked, good thing cause I had put the shoes on backwards, they fixed that and checked the rest. I assume that the rest is correct. As soon as I can afford it I want to change the rears out to disk. Is there a way to flush the whole brake system, some type of high pressure flush to push out all the old fluid and any foreign material?

 

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