[389goathead]

Has anyone had problems with new or rebuilt master cylinders?
I had a problem with the front brake locking up, proportioning valve was stuck, dirt in lines. Cleaned it and flushed lines, worked until this spring.
Calipers sticking, replaced with rebuilds, lost all brake pedal, plus old proportioning valve started leaking, I replaced it a unit from an A body, didn't help then with a Wilwood manual adjustable unit. Still no brakes on front, just rears. Appears to be a bad master cylinder. So far I have had 5 different ones on it from new to rebuilt and one from a car that was working. Pedal goes to the floor on all of them. No loss of fluid, no leaks. Have bleed over and over , no better. The rear brakes will lock up, no front. Replaced calipers with a 2nd set, same result. However If I clamp off the front hoses, I get full pedal ! If i take the clamp off the left side I get good pedal, it still locks up the rear first, but it will stop the car. If i clamp the left and release the right side, no pedal, car wont stop.
All these always lead back to a bad master cylinder, but everyone I try has the same result, low pressure seams to be the factor. Has anyone had this problem? Any suggestions....