Brake pedal goes to floor

[Kurt Deschler]

When I replaced my clutch master (pedal was going to floor), I took it
apart to see what the failure was. There was a small tear in the rubber
plunger, but not right on the edge as you might think. It was almost
centered between the edge and the piston. The edges of the plunger are
quite firm and the rubber is tough, but once a pinhole starts, the brake
fluid must cut through it like a water cutter.
	-Kurt

> **** I was not clear with my question.
> I wanted to know what happens inside the M/C to cause the "pedal to floor"
> symptom. What breaks inside the M/C?
>
> I'm assuming that the basic operation is similar to a hyperdermic needle
> syringe.
> My guess is that the rubber end of the plunger breaks, or dissolves, or
> folds over iteself, thus letting brake fluid slip past the rubber seal.
>
> Another possibility would be rusted and pitted brake cylinder bore, which
> would allow brake fluid to slip by the seal. But, this would cause a slow
> sinking of the brake pedal . . .not the fast sinking that I have.
>
> SJ