Brake Questions/Help

[WhiteFox012]

I've read through a lot of threads about the brakes but haven't seen any that fit the issue I'm having so sorry if it's been discussed.

I took the car out the other day and noticed the brakes felt funny. (2000 GT convertible with stock calipers and drilled/slotted rotors). I went into the store and came back out only to find my brake pedal now went to the floor. I pumped the pedal with the car running and the pedal got really firm. I left the store with brakes that felt off but we're stopping the car. After driving a few minutes, I lost brake pressure again and the pedal went to the floor with no stopping power. I pumped the brakes and the pedal went firm again. If I continued to press with the firm pedal I had no stopping power. If I pumped the pedal once or twice, they felt normal. If I didn't pump them, the pedal would go soft and I had no stopping power. If I pumped them 3-4 times, the pedal would go firm with no stopping power. I'm super confused as to where to begin with this thing.

Few things to note: I just bought this car and it sat while being for sale for at least a few months.
Also, every so often I will loose power steering. The previous owner said its been like that since he bought the car

 

[Neuron]

If no leaks then the master cylinder shouldn't let the pedal go to the floor I would think.

 

[Northwest_stang]

If it sat depends on how long or old the fluid is. If the brake fluid is dark you will need to replace it. However if it has been running bad fluid for a long time then the new fluid will more or less cause the seals in your master cylinder to give way.

This happened to me. So I go a new master cylinder, a crap ton of new fluid so I can flush the entire system. Also new transmission fluid. Our hydro boost system uses transmission fluid to add pressure to help stop. If your trans fluid is old/bad or has a lot of air in that system you will loose pressure.

So 50-75 for a reman master cylinder, 30 buck in brake fluid and 50 in trans fluid if that bad or old too

 

[1990 5.0 LX]

Sounds like the brake booster unit is adios.