Sable Brake Issues

Ok, I have taken my car now to the third place with no help - let's see if someone here can help me! Here's the story:
First time - I was backing out of a parking space and my brake pedal went to the floor, I brushed it off and kept going. A mile down the road I went to put my foot on the break to make a right hand turn, going approx. 25 mph, and the pedal went to the floor once again. So I continued going straight and pumped the break, thankfully they came back and I pulled off the road and was towed to the car repair. They were unable to duplicate the problem or find anything wrong - but went ahead and replaced the master cylinder just in case. NEXT - Three weeks later, driving down the road, 45 mph, getting ready to turn, put my foot on break, and it goes to the floor again! While panicking pump break (was in traffic) and I do get pulled off and stopped on the side of the road. When the tow truck gets there he notices fluid coming from underneath vehicle - looks and says it's coming from master cylinder. Take car back to the same place - the replace the master cylinder again (FREE of course). NOW - Driving down the road, 55mph - car is slightly vibrating, pull off, turn off engine, get out and look at car/tires/etc. - and I smell the same smell i smelled before - BRAKE FLUID!!! NOOO So i decided to drive a couple more miles up to the repair shop. Got in the car, and as soon as I started it and put my foot on the brake it went the floor! Then when I got to the repair shop it did the exact same thing for the repairman. But he still couldn't find anything wrong!!?!!?!?! So I took the car to a FORD dealership - they couldn't find anything wrong. Now it's at another Ford Dealership that supposedly my family trusts. Today they just came back saying they can't find anything wrong either. I don't know what to do - it's like i'm gambling with my life when I drive the thing! I don't want to drive it, but I don't have much of a choice either.
It's a 1996 Merc Sable GS

I had the pivot pin on the brake pedal fail so the whole pedal assembly had to be replaced. 98 Sable Wagon. Works fine now. If you are leaking fluid it is incredulous that a repairman cannot find the leak or point of failure.

Well it's not leaking now (supposedly), the only time it visibly leaked was after the first master cylinder was replaced. I haven't seen any leaks under the car, although I do smell the brake fluid smell on occassion. Could be residue left over I know, but almost a month later? I don't think so.

Well it's not leaking now (supposedly), the only time it visibly leaked was after the first master cylinder was replaced. I haven't seen any leaks under the car, although I do smell the brake fluid smell on occassion. Could be residue left over I know, but almost a month later? I don't think so.

Any fresh residue around the wheel calipers??
Also if you have a small pinhole in a line it may not leak a drip when stopped but spray out when you push the pedal. Try that a few times when parked on a clean surface.

I'm no expert but I had that happen on another vehicle.

The fluid is still full, so no apparant leakage of any kind they say.

Well if there are no leaks and if the brakes work and the pedal no longer goes to the floor it is likely that the problem was the Master Cylinder and is now functioning correctly so you should be OK. If the master cylinder was leaking it may have dripped into various nooks and crannies in the engine or engine compartment so you would continue to smell it, esp. when hot until you get the engine and undercarriage (steam) cleaned. Get someone to do that as you don't want to mess up any electronic items or you can just put up with the smell if not too bad. Drive carefully and check the fluid periodically.

I have a 2003 Merc Sable that has brake problems exactly as you have described (e.g. losing brake pedal). Had a mechanic inspect the brakes but can't find anything wrong. Yet still lose brakes sometimes. Did replacing the master cylinder on your Sable correct your brake problem?

I took the car to a FORD dealership and the only thing they could come up with is that since the Master Cylinder isn't FORD it's not working correctly with the vehicle. SO....put in a 3rd M.C., and since then - no problems. But I still drive carefully, just in case.

Sounds to me the master cylinder isn't getting bled after it is installed. This can cause fluid to come out the resv. and spill...And by a visable inspection how can a person tell whats wrong when the problem is on the inside? Most places have no ideal how to bleed brakes that have ABS. Some will tell you different. It is very important to have your brakes power flushed after a M/C is replaced, or the ABS assb.. More than half the people you ask about power flushing will have NO ideal what your talking about. Just about all manuals tell you about power flushing. May be something to check into and get done.