I have a 71 Duster with front disc rear drum manual brakes and I can't seem to get rid of a spongy pedal. I assumed that there was air in the lines so I tried gravity bleeding, manual bleeding, and vacuum bleeding the brakes to no avail. All linings are new. Is it possible to master cylinder is bypassing? If so shouldn't there be fluid at the back of the master where it mounts, because there is not any. Thanks in advance.

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"You know a car is really yours when you've touched every fastener on it." -David Freiburger

Your master cylinder could be bleeding across the front seal (from the front of the cylinder to the rear of the cylinder) without losing any brake fluid past the rear seal. Aside from bleeding, what brake work has been done recently? Did this pedal sponginess just appear recently, or is it a long-running problem?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

Ahhh...makes sense. The sponginess started recently. I installed new pads, rotors, and hoses on the front and everything on the rear is new, I converted to ten inch brakes.

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"You know a car is really yours when you've touched every fastener on it." -David Freiburger

H'mm. Well, plenty of chance to get new air in the system with that list of replaced parts. Are you bleeding in the correct order, starting with right rear, then left rear, right front, and left front? Have you done whatever is called for (I don't recall on that year) to purge the distribution block/proportioning valve of air?

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一期一会
Too many people who were born on third base actually believe they've hit a triple.

I bled it in the proper order, but I'll have to check out the service manual for bleeding the valve. Thanks for the help.

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"You know a car is really yours when you've touched every fastener on it." -David Freiburger