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Rear brake drag

874 views 3 replies 2 participants last post by  eppy 
#1 ·
I am having an issue with the rear brakes on my 32 ford. It has a 1981 corvette rear with disc and the front is Mustang II disc. I have a 7" booster an adjustable proportioning valve and 2 Lb residual valves one for the front and one for the rear. The issue is that with the vacuum connected to the booster the rear brakes do not fully disengage they drag, if I disconnect the vacuum line and press the pedal once or twice the rear brakes fully release. The front brakes work fine either way. I have no idea why it does this and hope someone can give some suggestions as to what to check for. I have adjusted the proportioning valve fully in both directions and it has no effect. The only way to release the rear brakes is to remove the vacuum line.
I do not know how much vacuum the line has but the car has a large cam. I thought it may be the e-brake, so I disconnected it, no difference.
 
#2 · (Edited)
Put a return spring on the pedal and make sure the pushrod is adjusted so it is just barely touching the master cylinder piston .Floor mounted pedals are notorious for not returning all the way. If everything is adjusted, and you have a pedal return spring installed already, then you may have a defective booster, it is supposed to fully retract when you let off the pedal. If the brakes will disengage when you pull the vacuum line off, that would indicate a defective air valve or sticky plunger.


Later, mikey
 
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