No brake pressure....

ok so i dont know if all this is related to each other or just two coincidences. the other day my emergency break light came on for no reason and has not turned off since, and than this morning i get in nd head out to work and realize that i have absolutely no break pressure under the pedal. the car will stop if i put the pedal all the way down to the floor. any help would ne greatly apreacheated.

What you call the "emergency break light" is misleading. It is, in fact, the brake system warning light, and if it comes on it means you have air in the system, or your emergency brake is on. In this case it means you are low on fluid.

Check your fluid level. You are low.

You will need to bleed the brakes to get the air out of the system.

You will also need to find the leak, or the reason you are low on fluid. It could be that low because your pads are completely worn and the pistons are holding all the fluid, or you have a leak somewhere.

I think you have a leak. Usually worn pads won't cause the fluid level to go down to the point where you can't stop (no pressure), but they could set off the brake light, indicating low fluid level. The fact that this happened so quickly (we'll assume) indicates a bad leak, imo.

can this also be caused by a failing master cylinder? also if it is a leak how could i go about locateing it?

It's possible the master cyl is failing, but you still have a leak. The fluid could be leaking into the vacuum booster, but would probably find it's way out the bottom of the booster, or onto your foot...

The only way to locate a leak that I know of is visually. You should see fluid under the car... somewhere. If not, add fluid and start bleeding the brakes. While bleeding you are constantly pressurizing the system and watch all the lines, all around. Sooner or later you'll see the fluid dripping from somewhere it's not supposed to.

If it were a bad master cylinder, the fluid wouldn't leak out, and the brake warning light probably wouldn't come on. The symptom of a bad MC is usually a slow loss of pressure, and when you get to the floor, there's no braking pressure. Pumping the brakes will let you stop the car with a bad MC.

Usually we don't hear about MCs going bad on Rivieras. Mine's still original at almost 190k miles.

Our Master Cylinder went out. The brake pedal would go down to about 1/2" off the floor and if I REALLY mashed it to the floor to stop.

Replaced it and we have good pedal now.

Check the fluid, fill if need be. Bleed all the calipers to make sure. If theres no air and the pedals still real soft way down, replace the Master Cylinder.