Rear brakes won't bleed?? Proportioning valve?


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Old 10-30-06, 04:32 PM
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Rear brakes won't bleed?? Proportioning valve?

We put new brakes on the rear of a 88 Mercury cougar and have tried to bleed the rear brakes many time unsuccessfully. We only get a tiny amount of fluid coming through. We put on a new master cylinder thinking that was the problem. Still no fluid. We took off a "t" that connects the brake line under the vehicle to the lines to the wheels and it still just occasionally drips so we know it's not in the wheel cylinders. We heard we have to bleed the proportioning valve but are not sure what this means. We know where the valve is but how is it bled and could this be the problem? How do we know if the valve could be bad? Any help would be appreciated.
 
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Old 10-30-06, 04:57 PM
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If you've checked all your brake lines for dents, etc, you can remove this valve, take it apart, and clean it. Sometimes debris can get in there, though rare, it does happen.

In mpost cars there is a floating piston inside that is spring loaded in down position when the brakes are off. When you apply the brakes, and the pressure builds in the brake system, the piston moves up. At some brake pressure, the piston covers the front port so no more pressure will go to the wheels. I assume that is to prevent the wheels getting locked in a panic stop.

There are small ports inside this valve that are probably clogged. Take it apart (noting what came from where) and clean it out.
 
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Old 10-31-06, 07:18 AM
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new brakes? need more info

What is new brakes? ... new shoes? new pads?

If so, why did you even attempt to bleed?

Were you having problem? Why new brakes?

Did you prime the new mc per directions that came with it? It is new and not from a junk yard? The push rod is in correctly, and you did not "adjust" it?

Don't worry about the proportion in valve, just make sure the car is not pointed down hill. Make sure it is level or front is higher than back.

You are bleeding all four wheels? You get good flow from the front? You close the bleeder valve before you assistant lets up on the pedle?

How does the pedel feel? Does is drive and stop ok? Maybe it functions as designed. The rear brakes do very little work. They really only keep your rear end in line with the front wheels on braking.

If you removed calipers, make sure bleeder is on the top. If it is at the bottom, you have left and right reversed.

write back.
 
 

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