I have a 1986 lincoln continental, how do u knw the master cylinder is bad? on 1990 Lincoln Continental

brake petal goes all the way to the floor, no fluid on tire or on the ground.

Asked by for the 1990 Lincoln Continental
1 answer
could be leaking at brk booster or pedal will go to the flow. could also be leaky wheel cyl if pedal goes to the floor. seek proper diag