Tasmin Breaks

My break pedal has a soft feel to it. Under light breaking it is normal but under moderate to hard breaking it has very little resistance. If you push it to the floor the breaks will lock up. If you pump the pedal it builds up some of its pressure. This problem has come on in the last few days and I have done no work to the breaking system. The fluid is full, but not so clean? My guess is its a bad break booster. Any other ideas?

Sounds like your booster is fine.
If your hydraulic fluid looks dirty it is contaminated. Before doing anything else flush and refill the brake system with fresh fluid and bleed the system.

With the key off, pump the brake pedal five or six times and hold it down when you start the car(what you are doing is relieving all the stored vacuum) Pedal should drop slightly when you start the motor. This indicates the diaphragm and valve in the booster are ok.

Engine running, press with light to moderate pressure on the brake pedal, continue holding pressure on the pedal for 15-20 seconds. If pedal continues dropping to the floor you have a leak in the hydraulic system of your brakes. If no fluid loss from the reservoir, you have an internally leaking master cylinder. Sometimes you can see a trail under the master cylinder on the face of the booster, other times you can see brake fluid dripping down from above the pedal linkage.

When you replace the master cylinder(as I'll betcha that's whats wrong) flush your entire brake system, bleed out new fluid from the bleeders at each wheel. Use a good fluid, and flush it every two years or more frequently in high humidity environments. All non synthetic brake fluids are hygroscopic,i.e. they absorb moisture, act like a sponge in a shower and pick it up and suck it in. This breaks down the molecules in the fluid. First thing the acids formed by the breakdown attack are the rubber, then the metal. Being as the seals in the master cylinder are under high pressure and closest to the exposed brake fluid(the vent in the cap) they suffer damage first.

Fluid driping from under the master cylinder. I guess I need to replace it.