Just changed the master cylinder since the truck had been sitting and the cylinder had begun to leak at the rear where it meets the booster. Since changing the cylinder twice in 2 days the same problem persists. The pedal pressure with the engine off is as it should be, solid feel and good return. With the engine on, the pedal has a soft feel and goes near the floor, the pedal return is far slower, and the performance is the real question. The brakes do perform better than with the previous cylinder, but there is either VERY little brake function, or they grab suddenly. Pedal feel is quite soft and there is no change in feel whether barely dragging the brake or up until they grab. Also, it is impossible to get the brakes to lock up or to perform a safe panic stop. We've bled in the proper sequence repeatedly, even at the prop valve. And yes, we did bench bleed the master. Help would be greatly appreciated, thank you
Aug 14, 2010 at 4:50 PM