Brake Pedal goes to floor as I apply brakes repeatedly

[Clipper81]

Hi, All.

'73 Squareback, with original front discs.
This started a couple of days ago. Previous to that, the brakes were fine.
Haven't worked on brake system in months. Reservoir is full. No sign of leaks.

When I step on the brake pedal, it is high and hard.
If I let off the brake pedal completely, and reapply, it is high and hard.

If I am braking. and I let up pressure a little bit, then apply more pressure, the pedal goes down a little bit.
If I do that 4 or 5 times in a row, the pedal goes down a little more each time, and eventually goes to the floor.

After that, if I let off the pedal completely, then step on it, it is high and hard again.

...Help! Anybody experience this? Do I need a new master cylinder?

Thanks...

[Rex lucy]

that or a rebuild would be a good idea.

[KTPhil]

Agreed, this sounds like a Master problem. While you are at it, replace the four soft lines and flush the system.

Replacement Masters may have different ports, so compare carefully, and perhaps change out a front line to make it fit.

[Clipper81]

Just a quick follow-up, so it might be stored in the collective wisdom base...

It did turn out to be the master cylinder Getting it out was a bit of a challenge; it had been in there awhile. But it solved the problem. Thanks to all!